Re: [PATCH] media: cedrus: Forbid setting new formats on busy queues

From: Hans Verkuil
Date: Thu Feb 14 2019 - 04:20:44 EST


On 2/14/19 10:18 AM, Paul Kocialkowski wrote:
> Hi,
>
> On Thu, 2019-02-14 at 09:59 +0100, Hans Verkuil wrote:
>> On 2/14/19 9:37 AM, Paul Kocialkowski wrote:
>>> Check that our queues are not busy before setting the format or return
>>> EBUSY if that's the case. This ensures that our format can't change
>>> once buffers are allocated for the queue.
>>>
>>> Signed-off-by: Paul Kocialkowski <paul.kocialkowski@xxxxxxxxxxx>
>>> ---
>>> drivers/staging/media/sunxi/cedrus/cedrus_video.c | 14 ++++++++++++++
>>> 1 file changed, 14 insertions(+)
>>>
>>> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_video.c b/drivers/staging/media/sunxi/cedrus/cedrus_video.c
>>> index b5cc79389d67..3420a938a613 100644
>>> --- a/drivers/staging/media/sunxi/cedrus/cedrus_video.c
>>> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_video.c
>>> @@ -282,8 +282,15 @@ static int cedrus_s_fmt_vid_cap(struct file *file, void *priv,
>>> {
>>> struct cedrus_ctx *ctx = cedrus_file2ctx(file);
>>> struct cedrus_dev *dev = ctx->dev;
>>> + struct vb2_queue *vq;
>>> int ret;
>>>
>>> + vq = v4l2_m2m_get_vq(ctx->fh.m2m_ctx, f->type);
>>> + if (!vq)
>>> + return -EINVAL;
>>
>> Can this ever happen?
>
> I guess not, or something would be very wrong.
> I have seen this check around when looking at how other drivers
> implement this, but it does seem overkill.
>
> Should I get rid of it in v2?

Yes please!

Regards,

Hans

>
> Cheers,
>
> Paul
>
>> Regards,
>>
>> Hans
>>
>>> + else if (vb2_is_busy(vq))
>>> + return -EBUSY;
>>> +
>>> ret = cedrus_try_fmt_vid_cap(file, priv, f);
>>> if (ret)
>>> return ret;
>>> @@ -299,8 +306,15 @@ static int cedrus_s_fmt_vid_out(struct file *file, void *priv,
>>> struct v4l2_format *f)
>>> {
>>> struct cedrus_ctx *ctx = cedrus_file2ctx(file);
>>> + struct vb2_queue *vq;
>>> int ret;
>>>
>>> + vq = v4l2_m2m_get_vq(ctx->fh.m2m_ctx, f->type);
>>> + if (!vq)
>>> + return -EINVAL;
>>> + else if (vb2_is_busy(vq))
>>> + return -EBUSY;
>>> +
>>> ret = cedrus_try_fmt_vid_out(file, priv, f);
>>> if (ret)
>>> return ret;
>>>