Re: [PATCH v2 03/12] staging: media: rkvdec: Helper for buffer queue busy check

[Andrzej Pietrasiewicz <andrzej.p@collabora.com>]

Hi Sebastian,

W dniu 12.01.2023 o 13:56, Sebastian Fricke pisze:
> Implement a helper function, wrapping around getting a vb2 queue and
> checking whether it is busy, to reduce the amount of code duplication in
> the driver.
> 
> Signed-off-by: Sebastian Fricke <sebastian.fricke@collabora.com>
> ---
>   drivers/staging/media/rkvdec/rkvdec.c | 21 ++++++++++++++-------
>   1 file changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/staging/media/rkvdec/rkvdec.c b/drivers/staging/media/rkvdec/rkvdec.c
> index 7bab7586918c..c849f6c20279 100644
> --- a/drivers/staging/media/rkvdec/rkvdec.c
> +++ b/drivers/staging/media/rkvdec/rkvdec.c
> @@ -27,6 +27,17 @@
>   #include "rkvdec.h"
>   #include "rkvdec-regs.h"
>   
> +static int rkvdec_queue_busy(struct rkvdec_ctx *ctx, enum v4l2_buf_type buf_type)
> +{
> +	struct vb2_queue *vq;
> +
> +	vq = v4l2_m2m_get_vq(ctx->fh.m2m_ctx, buf_type);
> +	if (vb2_is_busy(vq))
> +		return -EBUSY;
> +	else
> +		return 0;

Optionally you can use the ternary operator:

return vb2_is_busy(vg) ? -EBUSY : 0;

But then this new function essentially becomes a wrapper around extracting
the vq. The wrapper then encodes its result in the return value,
which is later decoded at call site to only return -EBUSY if the wrapper
returns -EBUSY and ignore the result if 0. This makes me think that
maybe you want a macro instead:

#define rkvdec_queue_busy(ctx, type) \
	vb2_is_busy(v4l2_m2m_get_vq((ctx)->fh.m2m_ctx, (type)))

and call it like this:

if (rkvdec_queue_busy(c, t))
	return -EBUSY;

> +}
> +
>   static int rkvdec_try_ctrl(struct v4l2_ctrl *ctrl)
>   {
>   	struct rkvdec_ctx *ctx = container_of(ctrl->handler, struct rkvdec_ctx, ctrl_hdl);
> @@ -311,13 +322,10 @@ static int rkvdec_s_capture_fmt(struct file *file, void *priv,
>   				struct v4l2_format *f)
>   {
>   	struct rkvdec_ctx *ctx = fh_to_rkvdec_ctx(priv);
> -	struct vb2_queue *vq;
>   	int ret;
>   
>   	/* Change not allowed if queue is busy */
> -	vq = v4l2_m2m_get_vq(ctx->fh.m2m_ctx,
> -			     V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE);
> -	if (vb2_is_busy(vq))
> +	if (rkvdec_queue_busy(ctx, V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE) != 0)

if you keep the current version you can drop the "!= 0"

Regards,

Andrzej

>   		return -EBUSY;
>   
>   	ret = rkvdec_try_capture_fmt(file, priv, f);
> @@ -335,7 +343,7 @@ static int rkvdec_s_output_fmt(struct file *file, void *priv,
>   	struct v4l2_m2m_ctx *m2m_ctx = ctx->fh.m2m_ctx;
>   	const struct rkvdec_coded_fmt_desc *desc;
>   	struct v4l2_format *cap_fmt;
> -	struct vb2_queue *peer_vq, *vq;
> +	struct vb2_queue *vq;
>   	int ret;
>   
>   	/*
> @@ -354,8 +362,7 @@ static int rkvdec_s_output_fmt(struct file *file, void *priv,
>   	 * queue, we can't allow doing so when the CAPTURE queue has buffers
>   	 * allocated.
>   	 */
> -	peer_vq = v4l2_m2m_get_vq(m2m_ctx, V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE);
> -	if (vb2_is_busy(peer_vq))
> +	if (rkvdec_queue_busy(ctx, V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE) != 0)
>   		return -EBUSY;
>   
>   	ret = rkvdec_try_output_fmt(file, priv, f);
>