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    SubjectRe: [announce][draft4] HVCS for inclusion in 2.6 tree
    Ryan Arnold wrote:
    > +int hvcs_free_partner_info(struct list_head *head)
    > +{
    > + struct hvcs_partner_info *pi;
    > + struct list_head *element;
    > +
    > + if (!head) {
    > + return -EINVAL;
    > + }

    style: single statements don't want braces


    > + while (!list_empty(head)) {
    > + element = head->next;
    > + pi = list_entry(element, struct hvcs_partner_info, node);
    > + list_del(element);
    > + kfree(pi);
    > + }

    list_for_each()


    > + return 0;
    > +}
    > +EXPORT_SYMBOL(hvcs_free_partner_info);
    > +
    > +/* Helper function for hvcs_get_partner_info */
    > +int hvcs_next_partner(unsigned int unit_address,
    > + unsigned long last_p_partition_ID,
    > + unsigned long last_p_unit_address, unsigned long *pi_buff)
    > +
    > +{
    > + long retval;
    > + retval = plpar_hcall_norets(H_VTERM_PARTNER_INFO, unit_address,
    > + last_p_partition_ID,
    > + last_p_unit_address, virt_to_phys(pi_buff));
    > + return hvcs_convert(retval);
    > +}
    > +
    > +/*
    > + * The unit_address parameter is the unit address of the vty-server vdevice
    > + * in whose partner information the caller is interested. This function
    > + * uses a pointer to a list_head instance in which to store the partner info.
    > + * This function returns non-zero on success, or if there is no partner info.
    > + *
    > + * Invocation of this function should always be followed by an invocation of
    > + * hvcs_free_partner_info() using a pointer to the SAME list head instance
    > + * that was used to store the partner_info list.
    > + */

    since these are exported functions, please use kernel-doc style so that
    they may be picked up by automated documentation tools


    > +int hvcs_get_partner_info(unsigned int unit_address, struct list_head *head,
    > + unsigned long *pi_buff)
    > +{
    > + /*
    > + * This is a page sized buffer to be passed to hvcall per invocation.
    > + * NOTE: the first long returned is unit_address. The second long
    > + * returned is the partition ID and starting with pi_buff[2] are
    > + * HVCS_CLC_LENGTH characters, which are diff size than the unsigned
    > + * long, hence the casting mumbojumbo you see later.
    > + */
    > + unsigned long last_p_partition_ID;
    > + unsigned long last_p_unit_address;
    > + struct hvcs_partner_info *next_partner_info = NULL;
    > + int more = 1;
    > + int retval;
    > +
    > + memset(pi_buff, 0x00, PAGE_SIZE);
    > + /* invalid parameters */
    > + if (!head)
    > + return -EINVAL;
    > +
    > + last_p_partition_ID = last_p_unit_address = ~0UL;
    > + INIT_LIST_HEAD(head);
    > +
    > + if (!pi_buff)
    > + return -ENOMEM;
    > +
    > + do {
    > + retval = hvcs_next_partner(unit_address, last_p_partition_ID,
    > + last_p_unit_address, pi_buff);
    > + if (retval) {
    > + /*
    > + * Don't indicate that we've failed if we have
    > + * any list elements.
    > + */
    > + if (!list_empty(head))
    > + return 0;
    > + return retval;
    > + }
    > +
    > + last_p_partition_ID = pi_buff[0];
    > + last_p_unit_address = pi_buff[1];
    > +
    > + /* This indicates that there are no further partners */
    > + if (last_p_partition_ID == ~0UL
    > + && last_p_unit_address == ~0UL)
    > + break;
    > +
    > + /* This is a very small struct and will be freed soon in
    > + * hvcs_free_partner_info(). */
    > + next_partner_info = kmalloc(sizeof(struct hvcs_partner_info),
    > + GFP_ATOMIC);
    > +
    > + if (!next_partner_info) {
    > + printk(KERN_WARNING "HVCONSOLE: kmalloc() failed to"
    > + " allocate partner info struct.\n");
    > + hvcs_free_partner_info(head);
    > + return -ENOMEM;
    > + }
    > +
    > + next_partner_info->unit_address
    > + = (unsigned int)last_p_unit_address;
    > + next_partner_info->partition_ID
    > + = (unsigned int)last_p_partition_ID;
    > +
    > + /* copy the Null-term char too */
    > + strncpy(&next_partner_info->location_code[0],
    > + (char *)&pi_buff[2],
    > + strlen((char *)&pi_buff[2]) + 1);
    > +
    > + list_add_tail(&(next_partner_info->node), head);
    > + next_partner_info = NULL;
    > +
    > + } while (more);
    > +
    > + return 0;
    > +}
    > +EXPORT_SYMBOL(hvcs_get_partner_info);
    > +
    > +/*
    > + * If this function is called once and -EINVAL is returned it may
    > + * indicate that the partner info needs to be refreshed for the
    > + * target unit address at which point the caller must invoke
    > + * hvcs_get_partner_info() and then call this function again. If,
    > + * for a second time, -EINVAL is returned then it indicates that
    > + * there is probably already a partner connection registered to a
    > + * different vty-server@ vdevice. It is also possible that a second
    > + * -EINVAL may indicate that one of the parms is not valid, for
    > + * instance if the link was removed between the vty-server@ vdevice
    > + * and the vty@ vdevice that you are trying to open. Don't shoot the
    > + * messenger. Firmware implemented it this way.
    > + */
    > +int hvcs_register_connection( unsigned int unit_address,
    > + unsigned int p_partition_ID, unsigned int p_unit_address)
    > +{
    > + long retval;
    > + retval = plpar_hcall_norets(H_REGISTER_VTERM, unit_address,
    > + p_partition_ID, p_unit_address);
    > + return hvcs_convert(retval);
    > +}
    > +EXPORT_SYMBOL(hvcs_register_connection);
    > +
    > +/*
    > + * If -EBUSY is returned continue to call this function
    > + * until 0 is returned.
    > + */
    > +int hvcs_free_connection(unsigned int unit_address)
    > +{
    > + long retval;
    > + retval = plpar_hcall_norets(H_FREE_VTERM, unit_address);
    > + return hvcs_convert(retval);
    > +}
    > +EXPORT_SYMBOL(hvcs_free_connection);

    > +/*
    > + * The hcall interface involves putting 8 chars into each of two registers.
    > + * We load up those 2 registers (in arch/ppc64/hvconsole.c) by casting char[16]
    > + * to long[2]. It would work without __ALIGNED__, but a little (tiny) bit
    > + * slower because an unaligned load is slower than aligned load.
    > + */
    > +#define __ALIGNED__ __attribute__((__aligned__(8)))

    does this definition really belong here?

    it also seems like the name would be likely to conflict with some
    existing symbol.


    > +/* Converged location code string length + 1 null terminator */
    > +#define CLC_LENGTH 80
    > +
    > +/*
    > + * How much data can firmware send with each hvc_put_chars()? Maybe this
    > + * should be moved into an architecture specific area.
    > + */
    > +#define HVCS_BUFF_LEN 16
    > +
    > +/*
    > + * This is the maximum amount of data we'll let the user send us (hvcs_write) at
    > + * once in a chunk as a sanity check.
    > + */
    > +#define HVCS_MAX_FROM_USER 4096
    > +
    > +/*
    > + * Be careful when adding flags to this line discipline. Don't add anything
    > + * that will cause echoing or we'll go into recursive loop echoing chars back
    > + * and forth with the console drivers.
    > + */
    > +static struct termios hvcs_tty_termios = {
    > + .c_iflag = IGNBRK | IGNPAR,
    > + .c_oflag = OPOST,
    > + .c_cflag = B38400 | CS8 | CREAD | HUPCL,
    > + .c_cc = INIT_C_CC
    > +};
    > +
    > +/*
    > + * This value is used to take the place of a command line parameter when the
    > + * module is inserted. It starts as -1 and stays as such if the user doesn't
    > + * specify a module insmod parameter. If they DO specify one then it is set to
    > + * the value of the integer passed in.
    > + */
    > +static int hvcs_parm_num_devs = -1;
    > +module_param(hvcs_parm_num_devs, int, 0);
    > +
    > +char hvcs_driver_name[] = "hvcs";
    > +char hvcs_device_node[] = "hvcs";
    > +char hvcs_driver_string[]
    > + = "IBM hvcs (Hypervisor Virtual Console Server) Driver";
    > +
    > +/* Status of partner info rescan triggered via sysfs. */
    > +static int hvcs_rescan_status = 0;

    implicitly rather than explicitly zero statics


    > +static struct tty_driver *hvcs_tty_driver;
    > +
    > +/*
    > + * This is used to associate a vty-server, as it is exposed to this driver, with
    > + * a preallocated tty_struct.index. The dev node and hvcs index numbers are not
    > + * re-used after device removal otherwise removing and adding a new one would
    > + * link a /dev/hvcs* entry to a different vty-server than it did before the
    > + * removal. Incidentally, a newly exposed vty-server will always map to an
    > + * incrementally higher /dev/hvcs* entry than the last exposed vty-server.
    > + */
    > +static int hvcs_struct_count = -1;
    > +
    > +/*
    > + * Used by the khvcsd to pick up I/O operations when the kernel_thread is
    > + * already awake but potentially shifted to TASK_INTERRUPTIBLE state.
    > + */
    > +static int hvcs_kicked = 0;

    implicitly rather than explicitly zero statics


    > +/* Used the the kthread construct for task operations */
    > +static struct task_struct *hvcs_task;
    > +
    > +/*
    > + * We allocate this for the use of all of the hvcs_structs when they fetch
    > + * partner info.
    > + */
    > +static unsigned long *hvcs_pi_buff;
    > +
    > +static spinlock_t hvcs_pi_lock;

    = SPIN_LOCK_UNLOCKED ?


    > +/* One vty-server per hvcs_struct */
    > +struct hvcs_struct {
    > + spinlock_t lock;
    > +
    > + /*
    > + * This index identifies this hvcs device as the complement to a
    > + * specific tty index.
    > + */
    > + unsigned int index;
    > +
    > + struct tty_struct *tty;
    > + unsigned int open_count;
    > +
    > + /*
    > + * Used to tell the driver kernel_thread what operations need to take
    > + * place upon this hvcs_struct instance.
    > + */
    > + int todo_mask;
    > +
    > + /*
    > + * This buffer is required so that when hvcs_write_room() reports that
    > + * it can send HVCS_BUFF_LEN characters that it will buffer the full
    > + * HVCS_BUFF_LEN characters if need be. This is essential for opost
    > + * writes since they do not do high level buffering and expect to be
    > + * able to send what the driver commits to sending buffering
    > + * [e.g. tab to space conversions in n_tty.c opost()].
    > + */
    > + char buffer[HVCS_BUFF_LEN];
    > + int chars_in_buffer;
    > +
    > + /*
    > + * Any variable below the kobject is valid before a tty is connected and
    > + * stays valid after the tty is disconnected. These shouldn't be
    > + * whacked until the koject refcount reaches zero though some entries
    > + * may be changed via sysfs initiatives.
    > + */
    > + struct kobject kobj; /* ref count & hvcs_struct lifetime */
    > + int connected; /* is the vty-server currently connected to a vty? */
    > + unsigned int p_unit_address; /* partner unit address */
    > + unsigned int p_partition_ID; /* partner partition ID */
    > + char p_location_code[CLC_LENGTH];
    > + struct list_head next; /* list management */
    > + struct vio_dev *vdev;
    > +};
    > +
    > +/* Required to back map a kobject to its containing object */
    > +#define from_kobj(kobj) container_of(kobj, struct hvcs_struct, kobj)
    > +
    > +static struct list_head hvcs_structs = LIST_HEAD_INIT(hvcs_structs);
    > +static spinlock_t hvcs_structs_lock;
    > +
    > +static void hvcs_unthrottle(struct tty_struct *tty);
    > +static void hvcs_throttle(struct tty_struct *tty);
    > +static irqreturn_t hvcs_handle_interrupt(int irq, void *dev_instance,
    > + struct pt_regs *regs);
    > +
    > +static int hvcs_write(struct tty_struct *tty, int from_user,
    > + const unsigned char *buf, int count);
    > +static int hvcs_write_room(struct tty_struct *tty);
    > +static int hvcs_chars_in_buffer(struct tty_struct *tty);
    > +
    > +static int hvcs_has_pi(struct hvcs_struct *hvcsd);
    > +static void hvcs_set_pi(struct hvcs_partner_info *pi,
    > + struct hvcs_struct *hvcsd);
    > +static int hvcs_get_pi(struct hvcs_struct *hvcsd);
    > +static int hvcs_rescan_devices_list(void);
    > +
    > +static int hvcs_partner_connect(struct hvcs_struct *hvcsd);
    > +static void hvcs_partner_free(struct hvcs_struct *hvcsd);
    > +
    > +static int hvcs_enable_device(struct hvcs_struct *hvcsd,
    > + uint32_t unit_address, unsigned int irq, struct vio_dev *dev);
    > +static void hvcs_final_close(struct hvcs_struct *hvcsd);
    > +
    > +static void destroy_hvcs_struct(struct kobject *kobj);
    > +static int hvcs_open(struct tty_struct *tty, struct file *filp);
    > +static void hvcs_close(struct tty_struct *tty, struct file *filp);
    > +static void hvcs_hangup(struct tty_struct * tty);
    > +
    > +static void hvcs_create_device_attrs(struct hvcs_struct *hvcsd);
    > +static void hvcs_remove_device_attrs(struct vio_dev *vdev);
    > +static void hvcs_create_driver_attrs(void);
    > +static void hvcs_remove_driver_attrs(void);
    > +
    > +static int __devinit hvcs_probe(struct vio_dev *dev,
    > + const struct vio_device_id *id);
    > +static int __devexit hvcs_remove(struct vio_dev *dev);
    > +static int __init hvcs_module_init(void);
    > +static void __exit hvcs_module_exit(void);
    > +
    > +#define HVCS_SCHED_READ 0x00000001
    > +#define HVCS_QUICK_READ 0x00000002
    > +#define HVCS_TRY_WRITE 0x00000004
    > +#define HVCS_READ_MASK (HVCS_SCHED_READ | HVCS_QUICK_READ)
    > +
    > +static void hvcs_kick(void)
    > +{
    > + hvcs_kicked = 1;
    > + wmb();
    > + wake_up_process(hvcs_task);
    > +}

    why not a semaphore or completion?


    > +static void hvcs_unthrottle(struct tty_struct *tty)
    > +{
    > + struct hvcs_struct *hvcsd = tty->driver_data;
    > + unsigned long flags;
    > +
    > + spin_lock_irqsave(&hvcsd->lock, flags);
    > + hvcsd->todo_mask |= HVCS_SCHED_READ;
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > + hvcs_kick();
    > +}
    > +
    > +static void hvcs_throttle(struct tty_struct *tty)
    > +{
    > + struct hvcs_struct *hvcsd = tty->driver_data;
    > + unsigned long flags;
    > +
    > + spin_lock_irqsave(&hvcsd->lock, flags);
    > + vio_disable_interrupts(hvcsd->vdev);
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > +}
    > +
    > +/*
    > + * If the device is being removed we don't have to worry about this interrupt
    > + * handler taking any further interrupts because they are disabled which means
    > + * the hvcs_struct will always be valid in this handler.
    > + */
    > +static irqreturn_t hvcs_handle_interrupt(int irq, void *dev_instance,
    > + struct pt_regs *regs)
    > +{
    > + struct hvcs_struct *hvcsd = dev_instance;
    > + unsigned long flags;
    > +
    > + spin_lock_irqsave(&hvcsd->lock, flags);
    > + vio_disable_interrupts(hvcsd->vdev);
    > + hvcsd->todo_mask |= HVCS_SCHED_READ;
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > + hvcs_kick();

    spin_lock_irqsave isn't necessary in interrupt handlers normally


    > + return IRQ_HANDLED;
    > +}
    > +
    > +/* This function must be called with the hvcsd->lock held */
    > +static void hvcs_try_write(struct hvcs_struct *hvcsd)
    > +{
    > + unsigned int unit_address = hvcsd->vdev->unit_address;
    > + struct tty_struct *tty = hvcsd->tty;
    > + int sent;
    > +
    > + if (hvcsd->todo_mask & HVCS_TRY_WRITE) {
    > + /* won't send partial writes */
    > + sent = hvc_put_chars(unit_address,
    > + &hvcsd->buffer[0],
    > + hvcsd->chars_in_buffer );
    > + if (sent > 0) {
    > + hvcsd->chars_in_buffer = 0;
    > + wmb();
    > + hvcsd->todo_mask &= ~(HVCS_TRY_WRITE);
    > + wmb();

    You are already inside a spinlock, why bother?


    > + /*
    > + * We are still obligated to deliver the data to the
    > + * hypervisor even if the tty has been closed because
    > + * we commited to delivering it. But don't try to wake
    > + * a non-existent tty.
    > + */
    > + if (tty) {
    > + if ((tty->flags & (1 << TTY_DO_WRITE_WAKEUP))
    > + && tty->ldisc.write_wakeup)
    > + (tty->ldisc.write_wakeup) (tty);
    > + wake_up_interruptible(&tty->write_wait);

    wouldn't just using up() be more simple?



    > + }
    > + }
    > + }
    > +}
    > +
    > +static int hvcs_io(struct hvcs_struct *hvcsd)
    > +{
    > + unsigned int unit_address;
    > + struct tty_struct *tty;
    > + char buf[HVCS_BUFF_LEN] __ALIGNED__;
    > + unsigned long flags;
    > + int got;
    > + int i;
    > +
    > + spin_lock_irqsave(&hvcsd->lock, flags);
    > +
    > + unit_address = hvcsd->vdev->unit_address;
    > + tty = hvcsd->tty;
    > +
    > + hvcs_try_write(hvcsd);
    > +
    > + if (!tty || test_bit(TTY_THROTTLED, &tty->flags)) {
    > + hvcsd->todo_mask &= ~(HVCS_READ_MASK);
    > + goto bail;
    > + } else if (!(hvcsd->todo_mask & (HVCS_READ_MASK)))
    > + goto bail;
    > +
    > + /* remove the read masks */
    > + hvcsd->todo_mask &= ~(HVCS_READ_MASK);
    > +
    > + if ((tty->flip.count + HVCS_BUFF_LEN) < TTY_FLIPBUF_SIZE) {
    > + got = hvc_get_chars(unit_address,
    > + &buf[0],
    > + HVCS_BUFF_LEN);
    > + for (i=0;got && i<got;i++)
    > + tty_insert_flip_char(tty, buf[i], TTY_NORMAL);
    > + }
    > +
    > + /* Give the TTY time to process the data we just sent. */
    > + if (got)
    > + hvcsd->todo_mask |= HVCS_QUICK_READ;
    > +
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > + if (tty->flip.count) {
    > + /* This is synch because tty->low_latency == 1 */
    > + tty_flip_buffer_push(tty);
    > + }
    > +
    > + if (!got) {
    > + /* Do this _after_ the flip_buffer_push */
    > + spin_lock_irqsave(&hvcsd->lock, flags);
    > + vio_enable_interrupts(hvcsd->vdev);
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > + }
    > +
    > + return hvcsd->todo_mask;
    > +
    > + bail:
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > + return hvcsd->todo_mask;
    > +}
    > +
    > +static int khvcsd(void *unused)
    > +{
    > + struct hvcs_struct *hvcsd = NULL;
    > + struct list_head *element;
    > + struct list_head *safe_temp;
    > + int hvcs_todo_mask;
    > + unsigned long structs_flags;
    > +
    > + __set_current_state(TASK_RUNNING);
    > +
    > + do {
    > + hvcs_todo_mask = 0;
    > + hvcs_kicked = 0;
    > + wmb();
    > +
    > + spin_lock_irqsave(&hvcs_structs_lock, structs_flags);
    > + list_for_each_safe(element, safe_temp, &hvcs_structs) {
    > + hvcsd = list_entry(element, struct hvcs_struct, next);
    > + hvcs_todo_mask |= hvcs_io(hvcsd);
    > + }
    > + spin_unlock_irqrestore(&hvcs_structs_lock, structs_flags);
    > +
    > + /*
    > + * If any of the hvcs adapters want to try a write or quick read
    > + * don't schedule(), yield a smidgen then execute the hvcs_io
    > + * thread again for those that want the write.
    > + */
    > + if (hvcs_todo_mask & (HVCS_TRY_WRITE | HVCS_QUICK_READ)) {
    > + yield();
    > + continue;
    > + }
    > +
    > + set_current_state(TASK_INTERRUPTIBLE);
    > + if (!hvcs_kicked)
    > + schedule();
    > + __set_current_state(TASK_RUNNING);

    This is essentially a busy loop.

    This thread has no condition to actually block on, which means it is
    running in a tight loop calling either yield() or schedule(). Not
    terrible, but it's far better to simply down_interruptible().


    > + } while (!kthread_should_stop());
    > +
    > + return 0;
    > +}
    > +
    > +static struct vio_device_id hvcs_driver_table[] __devinitdata= {
    > + {"serial-server", "hvterm2"},
    > + { 0, }
    > +};
    > +MODULE_DEVICE_TABLE(vio, hvcs_driver_table);
    > +
    > +/* callback when the kboject ref count reaches zero */
    > +static void destroy_hvcs_struct(struct kobject *kobj)
    > +{
    > + struct hvcs_struct *hvcsd = from_kobj(kobj);
    > + struct vio_dev *vdev;
    > + unsigned long flags;
    > +
    > + spin_lock_irqsave(&hvcsd->lock, flags);
    > +
    > + /* the list_del poisons the pointers */
    > + list_del(&(hvcsd->next));
    > +
    > + if (hvcsd->connected == 1) {
    > + hvcs_partner_free(hvcsd);
    > + printk(KERN_INFO "HVCS: Closed vty-server@%X and"
    > + " partner vty@%X:%d connection.\n",
    > + hvcsd->vdev->unit_address,
    > + hvcsd->p_unit_address,
    > + (unsigned int)hvcsd->p_partition_ID);
    > + }
    > + printk(KERN_INFO "HVCS: Destroyed hvcs_struct for vty-server@%X.\n",
    > + hvcsd->vdev->unit_address);
    > +
    > + vdev = hvcsd->vdev;
    > + hvcsd->vdev = NULL;
    > +
    > + hvcsd->p_unit_address = 0;
    > + hvcsd->p_partition_ID = 0;
    > + memset(&hvcsd->p_location_code[0], 0x00, CLC_LENGTH);
    > +
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > +
    > + hvcs_remove_device_attrs(vdev);
    > +
    > + kfree(hvcsd);
    > +}
    > +
    > +/* This function must be called with hvcsd->lock held. */
    > +static void hvcs_final_close(struct hvcs_struct *hvcsd)
    > +{
    > + vio_disable_interrupts(hvcsd->vdev);
    > + free_irq(hvcsd->vdev->irq, hvcsd);
    > +
    > + hvcsd->todo_mask = 0;
    > +
    > + /* These two may be redundant if the operation was a close. */
    > + if (hvcsd->tty) {
    > + hvcsd->tty->driver_data = NULL;
    > + hvcsd->tty = NULL;
    > + }
    > +
    > + hvcsd->open_count = 0;
    > +
    > + memset(&hvcsd->buffer[0], 0x00, HVCS_BUFF_LEN);
    > + hvcsd->chars_in_buffer = 0;
    > +}
    > +
    > +static struct kobj_type hvcs_kobj_type = {
    > + .release = destroy_hvcs_struct,
    > +};
    > +
    > +static int __devinit hvcs_probe(
    > + struct vio_dev *dev,
    > + const struct vio_device_id *id)
    > +{
    > + struct hvcs_struct *hvcsd;
    > + unsigned long structs_flags;
    > +
    > + if (!dev || !id) {
    > + printk(KERN_ERR "HVCS: probed with invalid parameter.\n");
    > + return -EPERM;
    > + }
    > +
    > + hvcsd = kmalloc(sizeof(*hvcsd), GFP_KERNEL);
    > + if (!hvcsd) {
    > + return -ENODEV;
    > + }

    style


    > + /* hvcsd->tty is zeroed out with the memset */
    > + memset(hvcsd, 0x00, sizeof(*hvcsd));
    > +
    > + hvcsd->lock = SPIN_LOCK_UNLOCKED;
    > + /* Automatically incs the refcount the first time */
    > + kobject_init(&hvcsd->kobj);
    > + /* Set up the callback for terminating the hvcs_struct's life */
    > + hvcsd->kobj.ktype = &hvcs_kobj_type;
    > +
    > + hvcsd->vdev = dev;
    > + dev->dev.driver_data = hvcsd;
    > +
    > + hvcsd->index = ++hvcs_struct_count;
    > + hvcsd->chars_in_buffer = 0;
    > + hvcsd->todo_mask = 0;
    > + hvcsd->connected = 0;
    > +
    > + /*
    > + * This will populate the hvcs_struct's partner info fields for the
    > + * first time.
    > + */
    > + if (hvcs_get_pi(hvcsd)) {
    > + printk(KERN_ERR "HVCS: Failed to fetch partner"
    > + " info for vty-server@%X on device probe.\n",
    > + hvcsd->vdev->unit_address);
    > + }
    > +
    > + /*
    > + * If a user app opens a tty that corresponds to this vty-server before
    > + * the hvcs_struct has been added to the devices list then the user app
    > + * will get -ENODEV.
    > + */
    > +
    > + spin_lock_irqsave(&hvcs_structs_lock, structs_flags);
    > +
    > + list_add_tail(&(hvcsd->next), &hvcs_structs);
    > +
    > + spin_unlock_irqrestore(&hvcs_structs_lock, structs_flags);
    > +
    > + hvcs_create_device_attrs(hvcsd);
    > +
    > + printk(KERN_INFO "HVCS: Added vty-server@%X.\n", dev->unit_address);
    > +
    > + /*
    > + * DON'T enable interrupts here because there is no user to receive the
    > + * data.
    > + */
    > + return 0;
    > +}
    > +
    > +static int __devexit hvcs_remove(struct vio_dev *dev)
    > +{

    remove returns an error??? I question the vio API builder...


    > + struct hvcs_struct *hvcsd = dev->dev.driver_data;
    > + unsigned long flags;
    > + struct kobject *kobjp;
    > + struct tty_struct *tty;
    > +
    > + if (!hvcsd)
    > + return -ENODEV;

    this should be a BUG(), no?


    > + /* By this time the vty-server won't be getting any more interrups */
    > +
    > + spin_lock_irqsave(&hvcsd->lock, flags);
    > +
    > + tty = hvcsd->tty;
    > +
    > + kobjp = &hvcsd->kobj;
    > +
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > +
    > + /*
    > + * Let the last holder of this object cause it to be removed, which
    > + * would probably be tty_hangup below.
    > + */
    > + kobject_put (kobjp);
    > +
    > + /*
    > + * The hangup is a scheduled function which will auto chain call
    > + * hvcs_hangup. The tty should always be valid at this time unless a
    > + * simultaneous tty close already cleaned up the hvcs_struct.
    > + */
    > + if (tty)
    > + tty_hangup(tty);
    > +
    > + printk(KERN_INFO "HVCS: vty-server@%X removed from the"
    > + " vio bus.\n", dev->unit_address);
    > + return 0;
    > +};
    > +
    > +static struct vio_driver hvcs_vio_driver = {
    > + .name = hvcs_driver_name,
    > + .id_table = hvcs_driver_table,
    > + .probe = hvcs_probe,
    > + .remove = hvcs_remove,
    > +};
    > +
    > +/* Only called from hvcs_get_pi please */
    > +static void hvcs_set_pi(struct hvcs_partner_info *pi, struct hvcs_struct *hvcsd)
    > +{
    > + int clclength;
    > +
    > + hvcsd->p_unit_address = pi->unit_address;
    > + hvcsd->p_partition_ID = pi->partition_ID;
    > + clclength = strlen(&pi->location_code[0]);
    > + if (clclength > CLC_LENGTH - 1)
    > + clclength = CLC_LENGTH - 1;
    > +
    > + /* copy the null-term char too */
    > + strncpy(&hvcsd->p_location_code[0],
    > + &pi->location_code[0], clclength + 1);
    > +}
    > +
    > +/*
    > + * Traverse the list and add the partner info that is found to the hvcs_struct
    > + * struct entry. NOTE: At this time I know that partner info will return a
    > + * single entry but in the future there may be multiple partner info entries per
    > + * vty-server and you'll want to zero out that list and reset it. If for some
    > + * reason you have an old version of this driver but there IS more than one
    > + * partner info then hvcsd->p_* will hold the last partner info data from the
    > + * firmware query. A good way to update this code would be to replace the three
    > + * partner info fields in hvcs_struct with a list of hvcs_partner_info
    > + * instances.
    > + *
    > + * This function must be called with the hvcsd->lock held.
    > + */
    > +static int hvcs_get_pi(struct hvcs_struct *hvcsd)
    > +{
    > + /* struct hvcs_partner_info *head_pi = NULL; */
    > + struct hvcs_partner_info *pi = NULL;
    > + unsigned int unit_address = hvcsd->vdev->unit_address;
    > + struct list_head head;
    > + unsigned long flags;
    > + int retval;
    > +
    > + spin_lock_irqsave(&hvcs_pi_lock, flags);
    > + if (!hvcs_pi_buff) {
    > + spin_unlock_irqrestore(&hvcs_pi_lock, flags);
    > + return -EFAULT;
    > + }
    > + retval = hvcs_get_partner_info(unit_address, &head, hvcs_pi_buff);
    > + spin_unlock_irqrestore(&hvcs_pi_lock, flags);
    > + if (retval) {
    > + printk(KERN_ERR "HVCS: Failed to fetch partner"
    > + " info for vty-server@%x.\n", unit_address);
    > + return retval;
    > + }
    > +
    > + /* nixes the values if the partner vty went away */
    > + hvcsd->p_unit_address = 0;
    > + hvcsd->p_partition_ID = 0;
    > +
    > + list_for_each_entry(pi, &head, node)
    > + hvcs_set_pi(pi, hvcsd);
    > +
    > + hvcs_free_partner_info(&head);
    > + return 0;
    > +}
    > +
    > +/*
    > + * This function is executed by the driver "rescan" sysfs entry. It shouldn't
    > + * be executed elsewhere, in order to prevent deadlock issues.
    > + */
    > +static int hvcs_rescan_devices_list(void)
    > +{
    > + struct hvcs_struct *hvcsd = NULL;
    > + unsigned long flags;
    > + unsigned long structs_flags;
    > +
    > + spin_lock_irqsave(&hvcs_structs_lock, structs_flags);
    > +
    > + list_for_each_entry(hvcsd, &hvcs_structs, next) {
    > + spin_lock_irqsave(&hvcsd->lock, flags);
    > + hvcs_get_pi(hvcsd);
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > + }
    > +
    > + spin_unlock_irqrestore(&hvcs_structs_lock, structs_flags);

    Isn't this double spin_lock_irqsave rather obviously silly?


    > + return 0;
    > +}
    > +
    > +/*
    > + * Farm this off into its own function because it could be more complex once
    > + * multiple partners support is added. This function should be called with
    > + * the hvcsd->lock held.
    > + */
    > +static int hvcs_has_pi(struct hvcs_struct *hvcsd)
    > +{
    > + if ((!hvcsd->p_unit_address) || (!hvcsd->p_partition_ID))
    > + return 0;
    > + return 1;
    > +}
    > +
    > +/*
    > + * NOTE: It is possible that the super admin removed a partner vty and then
    > + * added a different vty as the new partner.
    > + *
    > + * This function must be called with the hvcsd->lock held.
    > + */
    > +static int hvcs_partner_connect(struct hvcs_struct *hvcsd)
    > +{
    > + int retval;
    > + unsigned int unit_address = hvcsd->vdev->unit_address;
    > +
    > + /*
    > + * If there wasn't any pi when the device was added it doesn't meant
    > + * there isn't any now. This driver isn't notified when a new partner
    > + * vty is added to a vty-server so we discover changes on our own.
    > + * Please see comments in hvcs_register_connection() for justification
    > + * of this bizarre code.
    > + */
    > + retval = hvcs_register_connection(unit_address,
    > + hvcsd->p_partition_ID,
    > + hvcsd->p_unit_address);
    > + if (!retval) {
    > + hvcsd->connected = 1;
    > + return 0;
    > + } else if (retval != -EINVAL)
    > + return retval;
    > +
    > + /*
    > + * As per the spec re-get the pi and try again if -EINVAL after the
    > + * first connection attempt.
    > + */
    > + if (hvcs_get_pi(hvcsd))
    > + return -ENOMEM;
    > +
    > + if (!hvcs_has_pi(hvcsd))
    > + return -ENODEV;
    > +
    > + retval = hvcs_register_connection(unit_address,
    > + hvcsd->p_partition_ID,
    > + hvcsd->p_unit_address);
    > + if (retval != -EINVAL) {
    > + hvcsd->connected = 1;
    > + return retval;
    > + }
    > +
    > + /*
    > + * EBUSY is the most likely scenario though the vty could have been
    > + * removed or there really could be an hcall error due to the parameter
    > + * data but thanks to ambiguous firmware return codes we can't really
    > + * tell.
    > + */
    > + printk(KERN_INFO "HVCS: vty-server or partner"
    > + " vty is busy. Try again later.\n");
    > + return -EBUSY;
    > +}
    > +
    > +/* This function must be called with the hvcsd->lock held */
    > +static void hvcs_partner_free(struct hvcs_struct *hvcsd)
    > +{
    > + int retval;
    > + do {
    > + retval = hvcs_free_connection(hvcsd->vdev->unit_address);
    > + } while (retval == -EBUSY);
    > + hvcsd->connected = 0;
    > +}
    > +
    > +/* This helper function must be called WITHOUT the hvcsd->lock held */
    > +static int hvcs_enable_device(struct hvcs_struct *hvcsd, uint32_t unit_address,
    > + unsigned int irq, struct vio_dev *vdev)
    > +{
    > + unsigned long flags;
    > +
    > + /*
    > + * It is possible that the vty-server was removed between the time that
    > + * the conn was registered and now.
    > + */
    > + if (!request_irq(irq, &hvcs_handle_interrupt,
    > + SA_INTERRUPT, "ibmhvcs", hvcsd)) {
    > + /*
    > + * It is possible the vty-server was removed after the irq was
    > + * requested but before we have time to enable interrupts.
    > + */
    > + if (vio_enable_interrupts(vdev) == H_Success)
    > + return 0;
    > + else {
    > + printk(KERN_ERR "HVCS: int enable failed for"
    > + " vty-server@%X.\n", unit_address);
    > + free_irq(irq, hvcsd);
    > + }
    > + } else
    > + printk(KERN_ERR "HVCS: irq req failed for"
    > + " vty-server@%X.\n", unit_address);

    propagate return value from request_irq()


    > + spin_lock_irqsave(&hvcsd->lock, flags);
    > + hvcs_partner_free(hvcsd);
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > +
    > + return -ENODEV;
    > +
    > +}
    > +
    > +/*
    > + * This always increments the kobject ref count if the call is successful.
    > + * Please remember to dec when you are done with the instance.
    > + *
    > + * NOTICE: Do NOT hold either the hvcs_struct.lock or hvcs_structs_lock when
    > + * calling this function or you will get deadlock.
    > + */
    > +struct hvcs_struct *hvcs_get_by_index(int index)
    > +{
    > + struct hvcs_struct *hvcsd = NULL;
    > + struct list_head *element;
    > + struct list_head *safe_temp;
    > + unsigned long flags;
    > + unsigned long structs_flags;
    > +
    > + spin_lock_irqsave(&hvcs_structs_lock, structs_flags);
    > + /* We can immediately discard OOB requests */
    > + if (index >= 0 && index < HVCS_MAX_SERVER_ADAPTERS) {
    > + list_for_each_safe(element, safe_temp, &hvcs_structs) {
    > + hvcsd = list_entry(element, struct hvcs_struct, next);
    > + spin_lock_irqsave(&hvcsd->lock, flags);
    > + if (hvcsd->index == index) {
    > + kobject_get(&hvcsd->kobj);
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > + spin_unlock_irqrestore(&hvcs_structs_lock,
    > + structs_flags);
    > + return hvcsd;
    > + }
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > + }
    > + hvcsd = NULL;
    > + }
    > +
    > + spin_unlock_irqrestore(&hvcs_structs_lock, structs_flags);

    another spin_lock_irqsave() inside spin_lock_irqsave()


    > + return hvcsd;
    > +}
    > +
    > +/*
    > + * This is invoked via the tty_open interface when a user app connects to the
    > + * /dev node.
    > + */
    > +static int hvcs_open(struct tty_struct *tty, struct file *filp)
    > +{
    > + struct hvcs_struct *hvcsd = NULL;
    > + int retval = 0;
    > + unsigned long flags;
    > + unsigned int irq;
    > + struct vio_dev *vdev;
    > + unsigned long unit_address;
    > +
    > + if (tty->driver_data)
    > + goto fast_open;
    > +
    > + /*
    > + * Is there a vty-server that shares the same index?
    > + * This function increments the kobject index.
    > + */
    > + if (!(hvcsd = hvcs_get_by_index(tty->index))) {
    > + printk(KERN_WARNING "HVCS: open failed, no index.\n");
    > + return -ENODEV;
    > + }
    > +
    > + spin_lock_irqsave(&hvcsd->lock, flags);
    > +
    > + if (hvcsd->connected == 0)
    > + if ((retval = hvcs_partner_connect(hvcsd)))
    > + goto error_release;
    > +
    > + hvcsd->open_count = 1;
    > + hvcsd->tty = tty;
    > + tty->driver_data = hvcsd;
    > +
    > + /*
    > + * Set this driver to low latency so that we actually have a chance at
    > + * catching a throttled TTY after we flip_buffer_push. Otherwise the
    > + * flush_to_async may not execute until after the kernel_thread has
    > + * yielded and resumed the next flip_buffer_push resulting in data
    > + * loss.
    > + */
    > + tty->low_latency = 1;
    > +
    > + memset(&hvcsd->buffer[0], 0x3F, HVCS_BUFF_LEN);
    > +
    > + /*
    > + * Save these in the spinlock for the enable operations that need them
    > + * outside of the spinlock.
    > + */
    > + irq = hvcsd->vdev->irq;
    > + vdev = hvcsd->vdev;
    > + unit_address = hvcsd->vdev->unit_address;
    > +
    > + hvcsd->todo_mask |= HVCS_SCHED_READ;
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > +
    > + /*
    > + * This must be done outside of the spinlock because it requests irqs
    > + * and will grab the spinlcok and free the connection if it fails.
    > + */
    > + if ((hvcs_enable_device(hvcsd, unit_address, irq, vdev))) {
    > + kobject_put(&hvcsd->kobj);
    > + printk(KERN_WARNING "HVCS: enable device failed.\n");
    > + return -ENODEV;
    > + }

    propagate return value?


    > + goto open_success;
    > +
    > +fast_open:
    > + hvcsd = tty->driver_data;
    > +
    > + spin_lock_irqsave(&hvcsd->lock, flags);
    > + if (!kobject_get(&hvcsd->kobj)) {
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > + printk(KERN_ERR "HVCS: Kobject of open"
    > + " hvcs doesn't exist.\n");
    > + return -EFAULT; /* Is this the right return value? */
    > + }
    > +
    > + hvcsd->open_count++;
    > +
    > + hvcsd->todo_mask |= HVCS_SCHED_READ;
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > +open_success:
    > + hvcs_kick();
    > +
    > + printk(KERN_INFO "HVCS: vty-server@%X opened.\n",
    > + hvcsd->vdev->unit_address );
    > +
    > + return 0;
    > +
    > +error_release:
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > + kobject_put(&hvcsd->kobj);
    > +
    > + printk(KERN_WARNING "HVCS: HVCS partner connect failed.\n");
    > + return retval;
    > +}
    > +
    > +static void hvcs_close(struct tty_struct *tty, struct file *filp)
    > +{
    > + struct hvcs_struct *hvcsd;
    > + unsigned long flags;
    > + struct kobject *kobjp;
    > +
    > + /*
    > + * Is someone trying to close the file associated with this device after
    > + * we have hung up? If so tty->driver_data wouldn't be valid.
    > + */
    > + if (tty_hung_up_p(filp))
    > + return;
    > +
    > + /*
    > + * No driver_data means that this close was probably issued after a
    > + * failed hvcs_open by the tty layer's release_dev() api and we can just
    > + * exit cleanly.
    > + */
    > + if (!tty->driver_data)
    > + return;
    > +
    > + hvcsd = tty->driver_data;
    > +
    > + spin_lock_irqsave(&hvcsd->lock, flags);
    > + if (--hvcsd->open_count == 0) {
    > +
    > + /*
    > + * This line is important because it tells hvcs_open that this
    > + * device needs to be re-configured the next time hvcs_open is
    > + * called.
    > + */
    > + hvcsd->tty->driver_data = NULL;
    > +
    > + /*
    > + * NULL this early so that the kernel_thread doesn't try to
    > + * execute any operations on the TTY even though it is obligated
    > + * to deliver any pending I/O to the hypervisor.
    > + */
    > + hvcsd->tty = NULL;
    > +
    > + /*
    > + * Block the close until all the buffered data has been
    > + * delivered.
    > + */
    > + while(hvcsd->chars_in_buffer) {
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > +
    > + /*
    > + * Give the kernel thread the hvcs_struct so that it can
    > + * try to deliver the remaining data but block the close
    > + * operation by spinning in this function so that other
    > + * tty operations have to wait.
    > + */
    > + yield();
    > + spin_lock_irqsave(&hvcsd->lock, flags);
    > + }
    > +
    > + hvcs_final_close(hvcsd);
    > +
    > + } else if (hvcsd->open_count < 0) {
    > + printk(KERN_ERR "HVCS: vty-server@%X open_count: %d"
    > + " is missmanaged.\n",
    > + hvcsd->vdev->unit_address, hvcsd->open_count);
    > + }
    > + kobjp = &hvcsd->kobj;
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > +
    > + kobject_put(kobjp);
    > +}
    > +
    > +static void hvcs_hangup(struct tty_struct * tty)
    > +{
    > + struct hvcs_struct *hvcsd = tty->driver_data;
    > + unsigned long flags;
    > + int temp_open_count;
    > + struct kobject *kobjp;
    > +
    > + spin_lock_irqsave(&hvcsd->lock, flags);
    > + /* Preserve this so that we know how many kobject refs to put */
    > + temp_open_count = hvcsd->open_count;
    > +
    > + /*
    > + * Don't kobject put inside the spinlock because the destruction
    > + * callback may use the spinlock and it may get called before the
    > + * spinlock has been released. Get a pointer to the kobject and
    > + * kobject_put on that instead.
    > + */
    > + kobjp = &hvcsd->kobj;
    > +
    > + /* Calling this will drop any buffered data on the floor. */
    > + hvcs_final_close(hvcsd);
    > +
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > +
    > + /*
    > + * We need to kobject_put() for every open_count we have since the
    > + * tty_hangup() function doesn't invoke a close per open connection on a
    > + * non-console device.
    > + */
    > + while(temp_open_count) {
    > + --temp_open_count;
    > + /*
    > + * The final put will trigger destruction of the hvcs_struct.
    > + * NOTE: If this hangup was signaled from user space then the
    > + * final put will never happen.
    > + */
    > + kobject_put(kobjp);
    > + }
    > +}
    > +
    > +/*
    > + * NOTE: This is almost always from_user since user level apps interact with the
    > + * /dev nodes. I'm trusting that if hvcs_write gets called and interrupted by
    > + * hvcs_remove (which removes the target device and executes tty_hangup()) that
    > + * tty_hangup will allow hvcs_write time to complete execution before it
    > + * terminates our device.
    > + */
    > +static int hvcs_write(struct tty_struct *tty, int from_user,
    > + const unsigned char *buf, int count)
    > +{
    > + struct hvcs_struct *hvcsd = tty->driver_data;
    > + unsigned int unit_address;
    > + unsigned char *charbuf;
    > + unsigned long flags;
    > + int total_sent = 0;
    > + int tosend = 0;
    > + int result = 0;
    > +
    > + /*
    > + * If they don't check the return code off of their open they may
    > + * attempt this even if there is no connected device.
    > + */
    > + if (!hvcsd)
    > + return -ENODEV;
    > +
    > + /* Reasonable size to prevent user level flooding */
    > + if (count > HVCS_MAX_FROM_USER) {
    > + printk(KERN_WARNING "HVCS write: count being truncated to"
    > + " HVCS_MAX_FROM_USER.\n");
    > + count = HVCS_MAX_FROM_USER;
    > + }
    > +
    > + if (!from_user)
    > + charbuf = (unsigned char *)buf;
    > + else {
    > + charbuf = kmalloc(count, GFP_KERNEL);
    > + if (!charbuf) {
    > + printk(KERN_WARNING "HVCS: write -ENOMEM.\n");
    > + return -ENOMEM;
    > + }
    > +
    > + if (copy_from_user(charbuf, buf, count)) {
    > + kfree(charbuf);
    > + printk(KERN_WARNING "HVCS: write -EFAULT.\n");
    > + return -EFAULT;
    > + }
    > + }
    > +
    > + spin_lock_irqsave(&hvcsd->lock, flags);
    > +
    > + /*
    > + * Somehow an open succedded but the device was removed or the
    > + * connection terminated between the vty-server and partner vty during
    > + * the middle of a write operation? This is a crummy place to do this
    > + * but we want to keep it all in the spinlock.
    > + */
    > + if (hvcsd->open_count <= 0) {
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > + if (from_user)
    > + kfree(charbuf);
    > + return -ENODEV;
    > + }
    > +
    > + unit_address = hvcsd->vdev->unit_address;
    > +
    > + while (count > 0) {
    > + tosend = min(count, (HVCS_BUFF_LEN - hvcsd->chars_in_buffer));
    > + /*
    > + * No more space, this probably means that the last call to
    > + * hvcs_write() didn't succeed and the buffer was filled up.
    > + */
    > + if (!tosend)
    > + break;
    > +
    > + memcpy(&hvcsd->buffer[hvcsd->chars_in_buffer],
    > + &charbuf[total_sent],
    > + tosend);
    > +
    > + hvcsd->chars_in_buffer += tosend;
    > +
    > + result = 0;
    > +
    > + /*
    > + * If this is true then we don't want to try writing to the
    > + * hypervisor because that is the kernel_threads job now. We'll
    > + * just add to the buffer.
    > + */
    > + if (!(hvcsd->todo_mask & HVCS_TRY_WRITE))
    > + /* won't send partial writes */
    > + result = hvc_put_chars(unit_address,
    > + &hvcsd->buffer[0],
    > + hvcsd->chars_in_buffer);
    > +
    > + /*
    > + * Since we know we have enough room in hvcsd->buffer for
    > + * tosend we record that it was sent regardless of whether the
    > + * hypervisor actually took it because we have it buffered.
    > + */
    > + total_sent+=tosend;
    > + count-=tosend;
    > + if (result == 0) {
    > + hvcsd->todo_mask |= HVCS_TRY_WRITE;
    > + hvcs_kick();
    > + break;
    > + }
    > +
    > + hvcsd->chars_in_buffer = 0;
    > + /*
    > + * Test after the chars_in_buffer reset otherwise this could
    > + * deadlock our writes if hvc_put_chars fails.
    > + */
    > + if (result < 0)
    > + break;
    > + }
    > +
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > + if (from_user)
    > + kfree(charbuf);
    > +
    > + if (result == -1)
    > + return -EIO;
    > + else
    > + return total_sent;
    > +}
    > +
    > +/*
    > + * This is really asking how much can we guarentee that we can send or that we
    > + * absolutely WILL BUFFER if we can't send it. This driver MUST honor the
    > + * return value, hence the reason for hvcs_struct buffering.
    > + */
    > +static int hvcs_write_room(struct tty_struct *tty)
    > +{
    > + struct hvcs_struct *hvcsd = tty->driver_data;
    > + unsigned long flags;
    > + int retval;
    > +
    > + if (!hvcsd || hvcsd->open_count <= 0)
    > + return 0;
    > +
    > + spin_lock_irqsave(&hvcsd->lock, flags);
    > + retval = HVCS_BUFF_LEN - hvcsd->chars_in_buffer;
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > + return retval;
    > +}
    > +
    > +static int hvcs_chars_in_buffer(struct tty_struct *tty)
    > +{
    > + struct hvcs_struct *hvcsd = tty->driver_data;
    > + unsigned long flags;
    > + int retval;
    > +
    > + spin_lock_irqsave(&hvcsd->lock, flags);
    > + retval = hvcsd->chars_in_buffer;
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > + return retval;
    > +}
    > +
    > +static struct tty_operations hvcs_ops = {
    > + .open = hvcs_open,
    > + .close = hvcs_close,
    > + .hangup = hvcs_hangup,
    > + .write = hvcs_write,
    > + .write_room = hvcs_write_room,
    > + .chars_in_buffer = hvcs_chars_in_buffer,
    > + .unthrottle = hvcs_unthrottle,
    > + .throttle = hvcs_throttle,
    > +};
    > +
    > +static int __init hvcs_module_init(void)
    > +{
    > + int rc;
    > + int num_ttys_to_alloc;
    > +
    > + printk(KERN_INFO "Initializing %s\n", hvcs_driver_string);
    > +
    > + /* Has the user specified an overload with an insmod param? */
    > + if (hvcs_parm_num_devs <= 0 ||
    > + (hvcs_parm_num_devs > HVCS_MAX_SERVER_ADAPTERS)) {
    > + num_ttys_to_alloc = HVCS_DEFAULT_SERVER_ADAPTERS;
    > + } else
    > + num_ttys_to_alloc = hvcs_parm_num_devs;
    > +
    > + hvcs_tty_driver = alloc_tty_driver(num_ttys_to_alloc);
    > + if (!hvcs_tty_driver)
    > + return -ENOMEM;
    > +
    > + hvcs_tty_driver->owner = THIS_MODULE;
    > +
    > + hvcs_tty_driver->driver_name = hvcs_driver_name;
    > + hvcs_tty_driver->name = hvcs_device_node;
    > +
    > + /*
    > + * We'll let the system assign us a major number, indicated by leaving
    > + * it blank.
    > + */
    > +
    > + hvcs_tty_driver->minor_start = HVCS_MINOR_START;
    > + hvcs_tty_driver->type = TTY_DRIVER_TYPE_SYSTEM;
    > +
    > + /*
    > + * We role our own so that we DONT ECHO. We can't echo because the
    > + * device we are connecting to already echoes by default and this would
    > + * throw us into a horrible recursive echo-echo-echo loop.
    > + */
    > + hvcs_tty_driver->init_termios = hvcs_tty_termios;
    > + hvcs_tty_driver->flags = TTY_DRIVER_REAL_RAW;
    > +
    > + tty_set_operations(hvcs_tty_driver, &hvcs_ops);
    > +
    > + /*
    > + * The following call will result in sysfs entries that denote the
    > + * dynamically assigned major and minor numbers for our devices.
    > + */
    > + if (tty_register_driver(hvcs_tty_driver)) {
    > + printk(KERN_ERR "HVCS: registration "
    > + " as a tty driver failed.\n");
    > + put_tty_driver(hvcs_tty_driver);
    > + return rc;
    > + }
    > +
    > + hvcs_structs_lock = SPIN_LOCK_UNLOCKED;
    > +
    > + hvcs_pi_lock = SPIN_LOCK_UNLOCKED;
    > + hvcs_pi_buff = kmalloc(PAGE_SIZE, GFP_KERNEL);

    check return value


    > + hvcs_task = kthread_run(khvcsd, NULL, "khvcsd");
    > + if (IS_ERR(hvcs_task)) {
    > + printk("khvcsd creation failed. Driver not loaded.\n");
    > + kfree(hvcs_pi_buff);
    > + put_tty_driver(hvcs_tty_driver);
    > + return -EIO;
    > + }
    > +
    > + rc = vio_register_driver(&hvcs_vio_driver);
    > + /*
    > + * This needs to be done AFTER the vio_register_driver() call or else
    > + * the kobjects won't be initialized properly.
    > + */
    > + hvcs_create_driver_attrs();

    Are you sure about all this?? The whole order of initialization looks
    wrong.

    What happens if someone opens a tty before vio_register_driver() is
    finished?



    > + printk(KERN_INFO "HVCS: driver module inserted.\n");
    > +
    > + return rc;
    > +}
    > +
    > +static void __exit hvcs_module_exit(void)
    > +{
    > + unsigned long flags;
    > +
    > + /*
    > + * This driver receives hvcs_remove callbacks for each device upon
    > + * module removal.
    > + */
    > +
    > + /*
    > + * This synchronous operation will wake the khvcsd kthread if it is
    > + * asleep and will return when khvcsd has terminated.
    > + */
    > + kthread_stop(hvcs_task);
    > +
    > + spin_lock_irqsave(&hvcs_pi_lock, flags);
    > + kfree(hvcs_pi_buff);
    > + hvcs_pi_buff = NULL;
    > + spin_unlock_irqrestore(&hvcs_pi_lock, flags);
    > +
    > + hvcs_remove_driver_attrs();
    > +
    > + vio_unregister_driver(&hvcs_vio_driver);
    > +
    > + tty_unregister_driver(hvcs_tty_driver);
    > +
    > + put_tty_driver(hvcs_tty_driver);
    > +
    > + printk(KERN_INFO "HVCS: driver module removed.\n");
    > +}
    > +
    > +module_init(hvcs_module_init);
    > +module_exit(hvcs_module_exit);
    > +
    > +static inline struct hvcs_struct *from_vio_dev(struct vio_dev *viod)
    > +{
    > + return viod->dev.driver_data;
    > +}
    > +/* The sysfs interface for the driver and devices */
    > +
    > +static ssize_t hvcs_partner_vtys_show(struct device *dev, char *buf)
    > +{
    > + struct vio_dev *viod = to_vio_dev(dev);
    > + struct hvcs_struct *hvcsd = from_vio_dev(viod);
    > + unsigned long flags;
    > + int retval;
    > +
    > + spin_lock_irqsave(&hvcsd->lock, flags);
    > + retval = sprintf(buf, "%X\n", hvcsd->p_unit_address);
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > + return retval;
    > +}
    > +static DEVICE_ATTR(partner_vtys, S_IRUGO, hvcs_partner_vtys_show, NULL);
    > +
    > +static ssize_t hvcs_partner_clcs_show(struct device *dev, char *buf)
    > +{
    > + struct vio_dev *viod = to_vio_dev(dev);
    > + struct hvcs_struct *hvcsd = from_vio_dev(viod);
    > + unsigned long flags;
    > + int retval;
    > +
    > + spin_lock_irqsave(&hvcsd->lock, flags);
    > + retval = sprintf(buf, "%s\n", &hvcsd->p_location_code[0]);
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > + return retval;
    > +}
    > +static DEVICE_ATTR(partner_clcs, S_IRUGO, hvcs_partner_clcs_show, NULL);
    > +
    > +static ssize_t hvcs_current_vty_store(struct device *dev, const char * buf,
    > + size_t count)
    > +{
    > + /*
    > + * Don't need this feature at the present time because firmware doesn't
    > + * yet support multiple partners.
    > + */
    > + printk(KERN_INFO "HVCS: Denied current_vty change: -EPERM.\n");
    > + return -EPERM;
    > +}
    > +
    > +static ssize_t hvcs_current_vty_show(struct device *dev, char *buf)
    > +{
    > + struct vio_dev *viod = to_vio_dev(dev);
    > + struct hvcs_struct *hvcsd = from_vio_dev(viod);
    > + unsigned long flags;
    > + int retval;
    > +
    > + spin_lock_irqsave(&hvcsd->lock, flags);
    > + retval = sprintf(buf, "%s\n", &hvcsd->p_location_code[0]);
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > + return retval;
    > +}
    > +
    > +static DEVICE_ATTR(current_vty,
    > + S_IRUGO | S_IWUSR, hvcs_current_vty_show, hvcs_current_vty_store);
    > +
    > +static ssize_t hvcs_vterm_state_store(struct device *dev, const char *buf,
    > + size_t count)
    > +{
    > + struct vio_dev *viod = to_vio_dev(dev);
    > + struct hvcs_struct *hvcsd = from_vio_dev(viod);
    > + unsigned long flags;
    > +
    > + /* writing a '0' to this sysfs entry will result in the disconnect. */
    > + if (simple_strtol(buf, NULL, 0) != 0)
    > + return -EINVAL;
    > +
    > + spin_lock_irqsave(&hvcsd->lock, flags);
    > +
    > + if (hvcsd->open_count > 0) {
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > + printk(KERN_INFO "HVCS: vterm state unchanged. "
    > + "The hvcs device node is still in use.\n");
    > + return -EPERM;
    > + }
    > +
    > + if (hvcsd->connected == 0) {
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > + printk(KERN_INFO "HVCS: vterm state unchanged. The"
    > + " vty-server is not connected to a vty.\n");
    > + return -EPERM;
    > + }
    > +
    > + hvcs_partner_free(hvcsd);
    > + printk(KERN_INFO "HVCS: Closed vty-server@%X and"
    > + " partner vty@%X:%d connection.\n",
    > + hvcsd->vdev->unit_address,
    > + hvcsd->p_unit_address,
    > + (unsigned int)hvcsd->p_partition_ID);
    > +
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > + return count;
    > +}
    > +
    > +static ssize_t hvcs_vterm_state_show(struct device *dev, char *buf)
    > +{
    > + struct vio_dev *viod = to_vio_dev(dev);
    > + struct hvcs_struct *hvcsd = from_vio_dev(viod);
    > + unsigned long flags;
    > + int retval;
    > +
    > + spin_lock_irqsave(&hvcsd->lock, flags);
    > + retval = sprintf(buf, "%d\n", hvcsd->connected);
    > + spin_unlock_irqrestore(&hvcsd->lock, flags);
    > + return retval;
    > +}
    > +static DEVICE_ATTR(vterm_state, S_IRUGO | S_IWUSR,
    > + hvcs_vterm_state_show, hvcs_vterm_state_store);
    > +
    > +static struct attribute *hvcs_attrs[] = {
    > + &dev_attr_partner_vtys.attr,
    > + &dev_attr_partner_clcs.attr,
    > + &dev_attr_current_vty.attr,
    > + &dev_attr_vterm_state.attr,
    > + NULL,
    > +};
    > +
    > +static struct attribute_group hvcs_attr_group = {
    > + .attrs = hvcs_attrs,
    > +};
    > +
    > +static void hvcs_create_device_attrs(struct hvcs_struct *hvcsd)
    > +{
    > + struct vio_dev *vdev = hvcsd->vdev;
    > + sysfs_create_group(&vdev->dev.kobj, &hvcs_attr_group);
    > +}
    > +
    > +static void hvcs_remove_device_attrs(struct vio_dev *vdev)
    > +{
    > + sysfs_remove_group(&vdev->dev.kobj, &hvcs_attr_group);
    > +}
    > +
    > +static ssize_t hvcs_rescan_show(struct device_driver *ddp, char *buf)
    > +{
    > + /* A 1 means it is updating, a 0 means it is done updating */
    > + return snprintf(buf, PAGE_SIZE, "%d\n", hvcs_rescan_status);
    > +}
    > +
    > +static ssize_t hvcs_rescan_store(struct device_driver *ddp, const char * buf,
    > + size_t count)
    > +{
    > + if ((simple_strtol(buf, NULL, 0) != 1)
    > + && (hvcs_rescan_status != 0))
    > + return -EINVAL;
    > +
    > + hvcs_rescan_status = 1;
    > + printk(KERN_INFO "HVCS: rescanning partner info for all"
    > + " vty-servers.\n");
    > + hvcs_rescan_devices_list();
    > + hvcs_rescan_status = 0;
    > + return count;
    > +}
    > +static DRIVER_ATTR(rescan,
    > + S_IRUGO | S_IWUSR, hvcs_rescan_show, hvcs_rescan_store);
    > +
    > +static void hvcs_create_driver_attrs(void)
    > +{
    > + struct device_driver *driverfs = &(hvcs_vio_driver.driver);
    > + driver_create_file(driverfs, &driver_attr_rescan);
    > +}
    > +
    > +static void hvcs_remove_driver_attrs(void)
    > +{
    > + struct device_driver *driverfs = &(hvcs_vio_driver.driver);
    > + driver_remove_file(driverfs, &driver_attr_rescan);
    > +}

    -
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      Last update: 2005-03-22 14:04    [W:0.157 / U:2.060 seconds]
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