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SubjectRe: [patch v16 1/4] drivers: jtag: Add JTAG core driver
Hello Oleksandr-

I have a few comments below.

On Fri, Jan 12, 2018 at 07:08:26PM +0200, Oleksandr Shamray wrote:
> Initial patch for JTAG driver
> JTAG class driver provide infrastructure to support hardware/software
> JTAG platform drivers. It provide user layer API interface for flashing
> and debugging external devices which equipped with JTAG interface
> using standard transactions.
>
> Driver exposes set of IOCTL to user space for:
> - XFER:
> - SIR (Scan Instruction Register, IEEE 1149.1 Data Register scan);
> - SDR (Scan Data Register, IEEE 1149.1 Instruction Register scan);
> - RUNTEST (Forces the IEEE 1149.1 bus to a run state for a specified
> number of clocks).
> - SIOCFREQ/GIOCFREQ for setting and reading JTAG frequency.
>
> Driver core provides set of internal APIs for allocation and
> registration:
> - jtag_register;
> - jtag_unregister;
> - jtag_alloc;
> - jtag_free;
>
> Platform driver on registration with jtag-core creates the next
> entry in dev folder:
> /dev/jtagX
>
> Signed-off-by: Oleksandr Shamray <oleksandrs@mellanox.com>
> Signed-off-by: Jiri Pirko <jiri@mellanox.com>
> Acked-by: Philippe Ombredanne <pombredanne@nexb.com>

[..]

> +static long jtag_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> +{
> + struct jtag *jtag = file->private_data;
> + struct jtag_run_test_idle idle;
> + struct jtag_xfer xfer;
> + u8 *xfer_data;
> + u32 data_size;
> + u32 value;
> + int err;
> +
> + if (!arg)
> + return -EINVAL;
> +
> + switch (cmd) {
> + case JTAG_GIOCFREQ:
> + if (!jtag->ops->freq_get)
> + err = -EOPNOTSUPP;
> +
> + err = jtag->ops->freq_get(jtag, &value);
> + if (err)
> + break;
> +
> + if (put_user(value, (__u32 *)arg))
> + err = -EFAULT;
> + break;
> +
> + case JTAG_SIOCFREQ:
> + if (!jtag->ops->freq_set)
> + return -EOPNOTSUPP;
> +
> + if (get_user(value, (__u32 *)arg))
> + return -EFAULT;
> + if (value == 0)
> + return -EINVAL;
> +
> + err = jtag->ops->freq_set(jtag, value);
> + break;
> +
> + case JTAG_IOCRUNTEST:
> + if (!jtag->ops->idle)
> + return -EOPNOTSUPP;
> +
> + if (copy_from_user(&idle, (void *)arg,
> + sizeof(struct jtag_run_test_idle)))
> + return -EFAULT;
> +
> + if (idle.endstate > JTAG_STATE_PAUSEDR)
> + return -EINVAL;
> +
> + err = jtag->ops->idle(jtag, &idle);
> + break;
> +
> + case JTAG_IOCXFER:
> + if (!jtag->ops->xfer)

Are all ops optional? That seems bizarre. I would have expected at
least one callback to be required.

[..]
> +static int jtag_open(struct inode *inode, struct file *file)
> +{
> + struct jtag *jtag = container_of(file->private_data, struct jtag,
> + miscdev);
> +
> + if (mutex_lock_interruptible(&jtag->open_lock))
> + return -ERESTARTSYS;
> +
> + if (jtag->opened) {
> + mutex_unlock(&jtag->open_lock);
> + return -EBUSY;
> + }
> +
> + nonseekable_open(inode, file);
> + file->private_data = jtag;

These two can be moved out of the lock.

> + jtag->opened = true;
> + mutex_unlock(&jtag->open_lock);
> + return 0;
> +}
> +
> +static int jtag_release(struct inode *inode, struct file *file)
> +{
> + struct jtag *jtag = file->private_data;
> +
> + mutex_lock(&jtag->open_lock);
> + jtag->opened = false;
> + mutex_unlock(&jtag->open_lock);
> + return 0;
> +}
> +
> +static const struct file_operations jtag_fops = {
> + .owner = THIS_MODULE,
> + .open = jtag_open,
> + .release = jtag_release,
> + .llseek = noop_llseek,
> + .unlocked_ioctl = jtag_ioctl,
> +};
> +
> +struct jtag *jtag_alloc(size_t priv_size, const struct jtag_ops *ops)
> +{
> + struct jtag *jtag;
> +
> + jtag = kzalloc(sizeof(*jtag), GFP_KERNEL);

Did you mean to allocate: sizeof(*jtag) + priv_size?

> + if (!jtag)
> + return NULL;
> +
> + jtag->ops = ops;
> + return jtag;
> +}
> +EXPORT_SYMBOL_GPL(jtag_alloc);
> +
> +void jtag_free(struct jtag *jtag)
> +{
> + kfree(jtag);
> +}
> +EXPORT_SYMBOL_GPL(jtag_free);
> +
> +int jtag_register(struct jtag *jtag)
> +{
> + char *name;
> + int err;
> + int id;
> +
> + id = ida_simple_get(&jtag_ida, 0, 0, GFP_KERNEL);
> + if (id < 0)
> + return id;
> +
> + jtag->id = id;
> +
> + name = kzalloc(MAX_JTAG_NAME_LEN, GFP_KERNEL);
> + if (!name) {
> + err = -ENOMEM;
> + goto err_jtag_alloc;
> + }
> +
> + err = snprintf(name, MAX_JTAG_NAME_LEN, "jtag%d", id);
> + if (err < 0)
> + goto err_jtag_name;
> +
> + mutex_init(&jtag->open_lock);
> + jtag->miscdev.fops = &jtag_fops;
> + jtag->miscdev.minor = MISC_DYNAMIC_MINOR;
> + jtag->miscdev.name = name;
> +
> + err = misc_register(&jtag->miscdev);
> + if (err)
> + dev_err(jtag->dev, "Unable to register device\n");
> + else
> + return 0;
> + jtag->opened = false;

Well, this code flow is just confusing.

I suggest a redo with:

err = misc_register(&jtag->miscdev);
if (err) {
dev_err(jtag->dev, "Unable to register device\n");
goto err_jtag_name;
}

If you need to initialize 'opened', do it prior to misc_register.

Thanks,
Julia

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