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media: v4l2-mem2mem: Document that v4l2_m2m_get_vq() never returns NULL

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The v4l2_m2m_get_vq() never returns a NULL pointer, as the internal
get_queue_ctx() helper always returns a non-NULL pointer. Many drivers
check the return value against NULL, due to a combination of old code
and cargo-cult programming. Even v4l2-mem2mem.c contains unneeded NULL
checks.

Clarify the API by documenting explicitly that a NULL check is not
needed, and simplify the code by removing the unneeded NULL checks from
v4l2-mem2mem.c.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Stefan Klug <stefan.klug@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>
This commit is contained in:
Laurent Pinchart 2025-10-15 10:53:24 +03:00 • committed by Hans Verkuil
parent 082b86919b
commit 3662b54c16
2 changed files with 4 additions and 11 deletions
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12
drivers/media/v4l2-core/v4l2-mem2mem.c
View file

@ -123,13 +123,7 @@ static struct v4l2_m2m_queue_ctx *get_queue_ctx(struct v4l2_m2m_ctx *m2m_ctx,
struct vb2_queue *v4l2_m2m_get_vq(struct v4l2_m2m_ctx *m2m_ctx,
enum v4l2_buf_type type)
{
struct v4l2_m2m_queue_ctx *q_ctx;
q_ctx = get_queue_ctx(m2m_ctx, type);
if (!q_ctx)
return NULL;
return &q_ctx->q;
return &get_queue_ctx(m2m_ctx, type)->q;
}
EXPORT_SYMBOL(v4l2_m2m_get_vq);
@ -1285,8 +1279,6 @@ void v4l2_m2m_buf_queue(struct v4l2_m2m_ctx *m2m_ctx,
unsigned long flags;
q_ctx = get_queue_ctx(m2m_ctx, vbuf->vb2_buf.vb2_queue->type);
if (!q_ctx)
return;
spin_lock_irqsave(&q_ctx->rdy_spinlock, flags);
list_add_tail(&b->list, &q_ctx->rdy_queue);
@ -1388,8 +1380,6 @@ int v4l2_m2m_ioctl_remove_bufs(struct file *file, void *priv,
struct v4l2_fh *fh = file_to_v4l2_fh(file);
struct vb2_queue *q = v4l2_m2m_get_vq(fh->m2m_ctx, remove->type);
if (!q)
return -EINVAL;
if (q->type != remove->type)
return -EINVAL;

3
include/media/v4l2-mem2mem.h
View file

@ -153,6 +153,9 @@ void *v4l2_m2m_get_curr_priv(struct v4l2_m2m_dev *m2m_dev);
*
* @m2m_ctx: m2m context assigned to the instance given by struct &v4l2_m2m_ctx
* @type: type of the V4L2 buffer, as defined by enum &v4l2_buf_type
*
* This function returns the capture queue when @type is a capture type, and the
* output queue otherwise. It never returns a NULL pointer.
*/
struct vb2_queue *v4l2_m2m_get_vq(struct v4l2_m2m_ctx *m2m_ctx,
enum v4l2_buf_type type);