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SubjectRe: [PATCH] iio: core: centralize ioctl() calls to the main chardev
On Thu, 24 Sep 2020 11:41:55 +0300
Alexandru Ardelean <alexandru.ardelean@analog.com> wrote:

> The aim of this is to improve a bit the organization of ioctl() calls in
> IIO core. Currently the chardev is split across IIO core sub-modules/files.
> The main chardev has to be able to handle ioctl() calls, and if we need to
> add buffer ioctl() calls, this would complicate things.
>
> The 'industrialio-core.c' file will provide a 'iio_device_ioctl()' which
> will iterate over a list of ioctls registered with the IIO device. These
> can be event ioctl() or buffer ioctl() calls, or something else.
>
> Each ioctl() handler will have to return a IIO_IOCTL_UNHANDLED code (which
> is positive 1), if the ioctl() did not handle the call in any. This
> eliminates any potential ambiguities about negative error codes, which
> should fail the call altogether.
>
> If any ioctl() returns 0, it was considered that it was serviced
> successfully and the loop will exit.
>
> This change also moves the handling of the IIO_GET_EVENT_FD_IOCTL command
> inside 'industrialio-event.c', where this is better suited.
>
> This patch is a combination of 2 other patches from an older series:
> Patch 1: iio: core: add simple centralized mechanism for ioctl() handlers
> Link: https://lore.kernel.org/linux-iio/20200427131100.50845-6-alexandru.ardelean@analog.com/
> Patch 2: iio: core: use new common ioctl() mechanism
> Link: https://lore.kernel.org/linux-iio/20200427131100.50845-7-alexandru.ardelean@analog.com/
>
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> ---
>
> Note: since this is a change to the IIO core, we don't need to put this in
> right now; especially if there is a tight schedule, or we are too close to
> a merge window.

Looks good to me. As you suggest, lets let this one sit on the list for a
while though!

Jonathan

>
> drivers/iio/iio_core.h | 15 ++++++++-
> drivers/iio/industrialio-core.c | 56 ++++++++++++++++++++++++--------
> drivers/iio/industrialio-event.c | 28 +++++++++++++++-
> include/linux/iio/iio-opaque.h | 2 ++
> 4 files changed, 85 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/iio/iio_core.h b/drivers/iio/iio_core.h
> index fd9a5f1d5e51..fced02cadcc3 100644
> --- a/drivers/iio/iio_core.h
> +++ b/drivers/iio/iio_core.h
> @@ -17,6 +17,20 @@ struct iio_dev;
>
> extern struct device_type iio_device_type;
>
> +#define IIO_IOCTL_UNHANDLED 1
> +struct iio_ioctl_handler {
> + struct list_head entry;
> + long (*ioctl)(struct iio_dev *indio_dev, struct file *filp,
> + unsigned int cmd, unsigned long arg);
> +};
> +
> +long iio_device_ioctl(struct iio_dev *indio_dev, struct file *filp,
> + unsigned int cmd, unsigned long arg);
> +
> +void iio_device_ioctl_handler_register(struct iio_dev *indio_dev,
> + struct iio_ioctl_handler *h);
> +void iio_device_ioctl_handler_unregister(struct iio_ioctl_handler *h);
> +
> int __iio_add_chan_devattr(const char *postfix,
> struct iio_chan_spec const *chan,
> ssize_t (*func)(struct device *dev,
> @@ -74,7 +88,6 @@ static inline void iio_buffer_wakeup_poll(struct iio_dev *indio_dev) {}
> int iio_device_register_eventset(struct iio_dev *indio_dev);
> void iio_device_unregister_eventset(struct iio_dev *indio_dev);
> void iio_device_wakeup_eventset(struct iio_dev *indio_dev);
> -int iio_event_getfd(struct iio_dev *indio_dev);
>
> struct iio_event_interface;
> bool iio_event_enabled(const struct iio_event_interface *ev_int);
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index 261d3b17edc9..964a0a2d6f8b 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -1567,6 +1567,7 @@ struct iio_dev *iio_device_alloc(struct device *parent, int sizeof_priv)
> }
> dev_set_name(&dev->dev, "iio:device%d", dev->id);
> INIT_LIST_HEAD(&iio_dev_opaque->buffer_list);
> + INIT_LIST_HEAD(&iio_dev_opaque->ioctl_handlers);
>
> return dev;
> }
> @@ -1660,26 +1661,47 @@ static int iio_chrdev_release(struct inode *inode, struct file *filp)
> return 0;
> }
>
> -/* Somewhat of a cross file organization violation - ioctls here are actually
> - * event related */
> +void iio_device_ioctl_handler_register(struct iio_dev *indio_dev,
> + struct iio_ioctl_handler *h)
> +{
> + struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
> +
> + list_add_tail(&h->entry, &iio_dev_opaque->ioctl_handlers);
> +}
> +
> +void iio_device_ioctl_handler_unregister(struct iio_ioctl_handler *h)
> +{
> + list_del(&h->entry);
> +}
> +
> static long iio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
> {
> struct iio_dev *indio_dev = filp->private_data;
> - int __user *ip = (int __user *)arg;
> - int fd;
> + struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
> + struct iio_ioctl_handler *h;
> + int ret = -ENODEV;
> +
> + mutex_lock(&indio_dev->info_exist_lock);
>
> + /**
> + * The NULL check here is required to prevent crashing when a device
> + * is being removed while userspace would still have open file handles
> + * to try to access this device.
> + */
> if (!indio_dev->info)
> - return -ENODEV;
> -
> - if (cmd == IIO_GET_EVENT_FD_IOCTL) {
> - fd = iio_event_getfd(indio_dev);
> - if (fd < 0)
> - return fd;
> - if (copy_to_user(ip, &fd, sizeof(fd)))
> - return -EFAULT;
> - return 0;
> + goto out_unlock;
> +
> + ret = -EINVAL;
> + list_for_each_entry(h, &iio_dev_opaque->ioctl_handlers, entry) {
> + ret = h->ioctl(indio_dev, filp, cmd, arg);
> + if (ret != IIO_IOCTL_UNHANDLED)
> + break;
> }
> - return -EINVAL;
> +
> +out_unlock:
> + mutex_unlock(&indio_dev->info_exist_lock);
> +
> + return ret;
> }
>
> static const struct file_operations iio_buffer_fileops = {
> @@ -1796,6 +1818,9 @@ EXPORT_SYMBOL(__iio_device_register);
> **/
> void iio_device_unregister(struct iio_dev *indio_dev)
> {
> + struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
> + struct iio_ioctl_handler *h, *t;
> +
> cdev_device_del(&indio_dev->chrdev, &indio_dev->dev);
>
> mutex_lock(&indio_dev->info_exist_lock);
> @@ -1806,6 +1831,9 @@ void iio_device_unregister(struct iio_dev *indio_dev)
>
> indio_dev->info = NULL;
>
> + list_for_each_entry_safe(h, t, &iio_dev_opaque->ioctl_handlers, entry)
> + list_del(&h->entry);
> +
> iio_device_wakeup_eventset(indio_dev);
> iio_buffer_wakeup_poll(indio_dev);
>
> diff --git a/drivers/iio/industrialio-event.c b/drivers/iio/industrialio-event.c
> index 99ba657b8568..a2de2fd89067 100644
> --- a/drivers/iio/industrialio-event.c
> +++ b/drivers/iio/industrialio-event.c
> @@ -31,6 +31,7 @@
> * @flags: file operations related flags including busy flag.
> * @group: event interface sysfs attribute group
> * @read_lock: lock to protect kfifo read operations
> + * @@ioctl_handler: handler for event ioctl() calls
> */
> struct iio_event_interface {
> wait_queue_head_t wait;
> @@ -40,6 +41,7 @@ struct iio_event_interface {
> unsigned long flags;
> struct attribute_group group;
> struct mutex read_lock;
> + struct iio_ioctl_handler ioctl_handler;
> };
>
> bool iio_event_enabled(const struct iio_event_interface *ev_int)
> @@ -187,7 +189,7 @@ static const struct file_operations iio_event_chrdev_fileops = {
> .llseek = noop_llseek,
> };
>
> -int iio_event_getfd(struct iio_dev *indio_dev)
> +static int iio_event_getfd(struct iio_dev *indio_dev)
> {
> struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
> struct iio_event_interface *ev_int = iio_dev_opaque->event_interface;
> @@ -473,6 +475,24 @@ static void iio_setup_ev_int(struct iio_event_interface *ev_int)
> mutex_init(&ev_int->read_lock);
> }
>
> +static long iio_event_ioctl(struct iio_dev *indio_dev, struct file *filp,
> + unsigned int cmd, unsigned long arg)
> +{
> + int __user *ip = (int __user *)arg;
> + int fd;
> +
> + if (cmd == IIO_GET_EVENT_FD_IOCTL) {
> + fd = iio_event_getfd(indio_dev);
> + if (fd < 0)
> + return fd;
> + if (copy_to_user(ip, &fd, sizeof(fd)))
> + return -EFAULT;
> + return 0;
> + }
> +
> + return IIO_IOCTL_UNHANDLED;
> +}
> +
> static const char *iio_event_group_name = "events";
> int iio_device_register_eventset(struct iio_dev *indio_dev)
> {
> @@ -526,6 +546,10 @@ int iio_device_register_eventset(struct iio_dev *indio_dev)
> ev_int->group.attrs[attrn++] = &p->dev_attr.attr;
> indio_dev->groups[indio_dev->groupcounter++] = &ev_int->group;
>
> + ev_int->ioctl_handler.ioctl = iio_event_ioctl;
> + iio_device_ioctl_handler_register(&iio_dev_opaque->indio_dev,
> + &ev_int->ioctl_handler);
> +
> return 0;
>
> error_free_setup_event_lines:
> @@ -558,6 +582,8 @@ void iio_device_unregister_eventset(struct iio_dev *indio_dev)
>
> if (ev_int == NULL)
> return;
> +
> + iio_device_ioctl_handler_unregister(&ev_int->ioctl_handler);
> iio_free_chan_devattr_list(&ev_int->dev_attr_list);
> kfree(ev_int->group.attrs);
> kfree(ev_int);
> diff --git a/include/linux/iio/iio-opaque.h b/include/linux/iio/iio-opaque.h
> index f2e94196d31f..07c5a8e52ca8 100644
> --- a/include/linux/iio/iio-opaque.h
> +++ b/include/linux/iio/iio-opaque.h
> @@ -11,6 +11,7 @@
> * @channel_attr_list: keep track of automatically created channel
> * attributes
> * @chan_attr_group: group for all attrs in base directory
> + * @ioctl_handlers: ioctl handlers registered with the core handler
> * @debugfs_dentry: device specific debugfs dentry
> * @cached_reg_addr: cached register address for debugfs reads
> * @read_buf: read buffer to be used for the initial reg read
> @@ -22,6 +23,7 @@ struct iio_dev_opaque {
> struct list_head buffer_list;
> struct list_head channel_attr_list;
> struct attribute_group chan_attr_group;
> + struct list_head ioctl_handlers;
> #if defined(CONFIG_DEBUG_FS)
> struct dentry *debugfs_dentry;
> unsigned cached_reg_addr;

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