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

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Date:   Thu, 14 Feb 2019 10:20:36 +0100
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Paul Kocialkowski <paul.kocialkowski@...tlin.com>,
        linux-media@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-sunxi@...glegroups.com
Cc:     Maxime Ripard <maxime.ripard@...tlin.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH] media: cedrus: Forbid setting new formats on busy queues

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@...tlin.com>
>>> ---
>>>  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;
>>>