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SubjectRe: [PATCH v2 02/15] [media] lirc_dev: allow bufferless driver registration
On Fri, Jul 01, 2016 at 05:01:25PM +0900, Andi Shyti wrote:
> Some drivers don't necessarily need to have a FIFO managed buffer
> for their transfers. Drivers now should call
> lirc_register_bufferless_driver in order to handle the buffer
> themselves.
>
> The function works exaclty like lirc_register_driver except of
> the buffer allocation.

Indeed transmit-only devices don't need an input buffer, which is
just a waste of memory. However can't lirc_register_driver() figure
out from the features if the driver is capable of receiving, i.e.

int lirc_register_driver(struct lirc_driver *d)
{
int err, minor;

minor = lirc_allocate_driver(d);
if (minor < 0)
return minor;

if (d->features & LIRC_CAN_REC_MODE2) {
err = lirc_allocate_buffer(irctls[minor]);
if (err)
lirc_unregister_driver(minor);
}

return err ? err : minor;
}


Sean

>
> Signed-off-by: Andi Shyti <andi.shyti@samsung.com>
> ---
> drivers/media/rc/lirc_dev.c | 44 ++++++++++++++++++++++++++++++++++----------
> include/media/lirc_dev.h | 12 ++++++++++++
> 2 files changed, 46 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/media/rc/lirc_dev.c b/drivers/media/rc/lirc_dev.c
> index 5716978..fa562a3 100644
> --- a/drivers/media/rc/lirc_dev.c
> +++ b/drivers/media/rc/lirc_dev.c
> @@ -205,12 +205,14 @@ err_out:
>
> static int lirc_allocate_buffer(struct irctl *ir)
> {
> - int err;
> + int err = 0;
> int bytes_in_key;
> unsigned int chunk_size;
> unsigned int buffer_size;
> struct lirc_driver *d = &ir->d;
>
> + mutex_lock(&lirc_dev_lock);
> +
> bytes_in_key = BITS_TO_LONGS(d->code_length) +
> (d->code_length % 8 ? 1 : 0);
> buffer_size = d->buffer_size ? d->buffer_size : BUFLEN / bytes_in_key;
> @@ -220,21 +222,26 @@ static int lirc_allocate_buffer(struct irctl *ir)
> ir->buf = d->rbuf;
> } else {
> ir->buf = kmalloc(sizeof(struct lirc_buffer), GFP_KERNEL);
> - if (!ir->buf)
> - return -ENOMEM;
> + if (!ir->buf) {
> + err = -ENOMEM;
> + goto out;
> + }
>
> err = lirc_buffer_init(ir->buf, chunk_size, buffer_size);
> if (err) {
> kfree(ir->buf);
> - return err;
> + goto out;
> }
> }
> ir->chunk_size = ir->buf->chunk_size;
>
> - return 0;
> +out:
> + mutex_unlock(&lirc_dev_lock);
> +
> + return err;
> }
>
> -int lirc_register_driver(struct lirc_driver *d)
> +static int lirc_allocate_driver(struct lirc_driver *d)
> {
> struct irctl *ir;
> int minor;
> @@ -342,10 +349,6 @@ int lirc_register_driver(struct lirc_driver *d)
> /* some safety check 8-) */
> d->name[sizeof(d->name)-1] = '\0';
>
> - err = lirc_allocate_buffer(ir);
> - if (err)
> - goto out_lock;
> -
> if (d->features == 0)
> d->features = LIRC_CAN_REC_LIRCCODE;
>
> @@ -385,8 +388,29 @@ out_lock:
> out:
> return err;
> }
> +
> +int lirc_register_driver(struct lirc_driver *d)
> +{
> + int err, minor;
> +
> + minor = lirc_allocate_driver(d);
> + if (minor < 0)
> + return minor;
> +
> + err = lirc_allocate_buffer(irctls[minor]);
> + if (err)
> + lirc_unregister_driver(minor);
> +
> + return err ? err : minor;
> +}
> EXPORT_SYMBOL(lirc_register_driver);
>
> +int lirc_register_bufferless_driver(struct lirc_driver *d)
> +{
> + return lirc_allocate_driver(d);
> +}
> +EXPORT_SYMBOL(lirc_register_bufferless_driver);
> +
> int lirc_unregister_driver(int minor)
> {
> struct irctl *ir;
> diff --git a/include/media/lirc_dev.h b/include/media/lirc_dev.h
> index 0ab59a5..8bed57a 100644
> --- a/include/media/lirc_dev.h
> +++ b/include/media/lirc_dev.h
> @@ -214,6 +214,18 @@ struct lirc_driver {
> */
> extern int lirc_register_driver(struct lirc_driver *d);
>
> +/* int lirc_register_bufferless_driver - allocates a lirc bufferless driver
> + * @d: reference to the lirc_driver to initialize
> + *
> + * The difference between lirc_register_driver and
> + * lirc_register_bufferless_driver is that the latter doesn't allocate any
> + * buffer, which means that the driver using the lirc_driver should take care of
> + * it by itself.
> + *
> + * returns 0 on success or a the negative errno number in case of failure.
> + */
> +extern int lirc_register_bufferless_driver(struct lirc_driver *d);
> +
> /* returns negative value on error or 0 if success
> */
> extern int lirc_unregister_driver(int minor);
> --
> 2.8.1

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