[PATCH] omap3isp: video: Don't WARN() on unknown pixel formats

[PATCH] omap3isp: video: Don't WARN() on unknown pixel formats

[Laurent Pinchart]

When mapping from a V4L2 pixel format to a media bus format in the
VIDIOC_TRY_FMT and VIDIOC_S_FMT handlers, the requested format may be
unsupported by the driver. Return a hardcoded format instead of
WARN()ing in that case.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
 drivers/media/video/omap3isp/ispvideo.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/media/video/omap3isp/ispvideo.c b/drivers/media/video/omap3isp/ispvideo.c
index d100072..ffe7ce9 100644
--- a/drivers/media/video/omap3isp/ispvideo.c
+++ b/drivers/media/video/omap3isp/ispvideo.c
@@ -210,14 +210,14 @@ static void isp_video_pix_to_mbus(const struct v4l2_pix_format *pix,
 	mbus->width = pix->width;
 	mbus->height = pix->height;
 
-	for (i = 0; i < ARRAY_SIZE(formats); ++i) {
+	/* Skip the last format in the loop so that it will be selected if no
+	 * match is found.
+	 */
+	for (i = 0; i < ARRAY_SIZE(formats) - 1; ++i) {
 		if (formats[i].pixelformat == pix->pixelformat)
 			break;
 	}
 
-	if (WARN_ON(i == ARRAY_SIZE(formats)))
-		return;
-
 	mbus->code = formats[i].code;
 	mbus->colorspace = pix->colorspace;
 	mbus->field = pix->field;
-- 
Regards,

Laurent Pinchart

Re: [PATCH] omap3isp: video: Don't WARN() on unknown pixel formats

[Sakari Ailus]

Thanks for the patch, Laurent!

On Mon, Nov 28, 2011 at 12:37:34PM +0100, Laurent Pinchart wrote:
> When mapping from a V4L2 pixel format to a media bus format in the
> VIDIOC_TRY_FMT and VIDIOC_S_FMT handlers, the requested format may be
> unsupported by the driver. Return a hardcoded format instead of
> WARN()ing in that case.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> ---
>  drivers/media/video/omap3isp/ispvideo.c |    8 ++++----
>  1 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/media/video/omap3isp/ispvideo.c b/drivers/media/video/omap3isp/ispvideo.c
> index d100072..ffe7ce9 100644
> --- a/drivers/media/video/omap3isp/ispvideo.c
> +++ b/drivers/media/video/omap3isp/ispvideo.c
> @@ -210,14 +210,14 @@ static void isp_video_pix_to_mbus(const struct v4l2_pix_format *pix,
>  	mbus->width = pix->width;
>  	mbus->height = pix->height;
>  
> -	for (i = 0; i < ARRAY_SIZE(formats); ++i) {
> +	/* Skip the last format in the loop so that it will be selected if no
> +	 * match is found.
> +	 */
> +	for (i = 0; i < ARRAY_SIZE(formats) - 1; ++i) {
>  		if (formats[i].pixelformat == pix->pixelformat)
>  			break;
>  	}
>  
> -	if (WARN_ON(i == ARRAY_SIZE(formats)))
> -		return;
> -
>  	mbus->code = formats[i].code;
>  	mbus->colorspace = pix->colorspace;
>  	mbus->field = pix->field;

In case of setting or trying an invalid format, instead of selecting a
default format, shouldn't we leave the format unchanced --- the current
setting is valid after all.

-- 
Sakari Ailus
e-mail: sakari.ailus@iki.fi	jabber/XMPP/Gmail: sailus@retiisi.org.uk

Re: [PATCH] omap3isp: video: Don't WARN() on unknown pixel formats

[Laurent Pinchart]

Hi Sakari,

On Monday 28 November 2011 17:01:12 Sakari Ailus wrote:
> On Mon, Nov 28, 2011 at 12:37:34PM +0100, Laurent Pinchart wrote:
> > When mapping from a V4L2 pixel format to a media bus format in the
> > VIDIOC_TRY_FMT and VIDIOC_S_FMT handlers, the requested format may be
> > unsupported by the driver. Return a hardcoded format instead of
> > WARN()ing in that case.
> > 
> > Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > ---
> > 
> >  drivers/media/video/omap3isp/ispvideo.c |    8 ++++----
> >  1 files changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/media/video/omap3isp/ispvideo.c
> > b/drivers/media/video/omap3isp/ispvideo.c index d100072..ffe7ce9 100644
> > --- a/drivers/media/video/omap3isp/ispvideo.c
> > +++ b/drivers/media/video/omap3isp/ispvideo.c
> > @@ -210,14 +210,14 @@ static void isp_video_pix_to_mbus(const struct
> > v4l2_pix_format *pix,
> > 
> >  	mbus->width = pix->width;
> >  	mbus->height = pix->height;
> > 
> > -	for (i = 0; i < ARRAY_SIZE(formats); ++i) {
> > +	/* Skip the last format in the loop so that it will be selected if no
> > +	 * match is found.
> > +	 */
> > +	for (i = 0; i < ARRAY_SIZE(formats) - 1; ++i) {
> > 
> >  		if (formats[i].pixelformat == pix->pixelformat)
> >  		
> >  			break;
> >  	
> >  	}
> > 
> > -	if (WARN_ON(i == ARRAY_SIZE(formats)))
> > -		return;
> > -
> > 
> >  	mbus->code = formats[i].code;
> >  	mbus->colorspace = pix->colorspace;
> >  	mbus->field = pix->field;
> 
> In case of setting or trying an invalid format, instead of selecting a
> default format, shouldn't we leave the format unchanced --- the current
> setting is valid after all.

TRY/SET operations must succeed. The format we select when an invalid format 
is requested isn't specified. We could keep the current format, but wouldn't 
that be more confusing for applications ? The format they would get in 
response to a TRY/SET operation would then potentially depend on the previous 
SET operations.

-- 
Regards,

Laurent Pinchart

Re: [PATCH] omap3isp: video: Don't WARN() on unknown pixel formats

[Sakari Ailus]

Laurent Pinchart wrote:
> Hi Sakari,
> 
> On Monday 28 November 2011 17:01:12 Sakari Ailus wrote:
>> On Mon, Nov 28, 2011 at 12:37:34PM +0100, Laurent Pinchart wrote:
>>> When mapping from a V4L2 pixel format to a media bus format in the
>>> VIDIOC_TRY_FMT and VIDIOC_S_FMT handlers, the requested format may be
>>> unsupported by the driver. Return a hardcoded format instead of
>>> WARN()ing in that case.
>>>
>>> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>>> ---
>>>
>>>  drivers/media/video/omap3isp/ispvideo.c |    8 ++++----
>>>  1 files changed, 4 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/media/video/omap3isp/ispvideo.c
>>> b/drivers/media/video/omap3isp/ispvideo.c index d100072..ffe7ce9 100644
>>> --- a/drivers/media/video/omap3isp/ispvideo.c
>>> +++ b/drivers/media/video/omap3isp/ispvideo.c
>>> @@ -210,14 +210,14 @@ static void isp_video_pix_to_mbus(const struct
>>> v4l2_pix_format *pix,
>>>
>>>  	mbus->width = pix->width;
>>>  	mbus->height = pix->height;
>>>
>>> -	for (i = 0; i < ARRAY_SIZE(formats); ++i) {
>>> +	/* Skip the last format in the loop so that it will be selected if no
>>> +	 * match is found.
>>> +	 */
>>> +	for (i = 0; i < ARRAY_SIZE(formats) - 1; ++i) {
>>>
>>>  		if (formats[i].pixelformat == pix->pixelformat)
>>>  		
>>>  			break;
>>>  	
>>>  	}
>>>
>>> -	if (WARN_ON(i == ARRAY_SIZE(formats)))
>>> -		return;
>>> -
>>>
>>>  	mbus->code = formats[i].code;
>>>  	mbus->colorspace = pix->colorspace;
>>>  	mbus->field = pix->field;
>>
>> In case of setting or trying an invalid format, instead of selecting a
>> default format, shouldn't we leave the format unchanced --- the current
>> setting is valid after all.
> 
> TRY/SET operations must succeed. The format we select when an invalid format 
> is requested isn't specified. We could keep the current format, but wouldn't 
> that be more confusing for applications ? The format they would get in 
> response to a TRY/SET operation would then potentially depend on the previous 
> SET operations.

I don't think a change to something that has nothing to do what was
requested is better than not changing it. The application has requested
a particular format; changing it to something else isn't useful for the
application. And if the application would try more than invalid format
in a row, they both would yield to the same default format.

I would personally not change it.

What I can find in the spec is this:

"When the application calls the VIDIOC_S_FMT ioctl with a pointer to a
v4l2_format structure the driver checks and adjusts the parameters
against hardware abilities."

I wonder how other drivers behave.

-- 
Sakari Ailus
sakari.ailus@iki.fi

Re: [PATCH] omap3isp: video: Don't WARN() on unknown pixel formats

[Laurent Pinchart]

Hi Sakari,

On Wednesday 30 November 2011 09:35:38 Sakari Ailus wrote:
> Laurent Pinchart wrote:
> > On Monday 28 November 2011 17:01:12 Sakari Ailus wrote:
> >> On Mon, Nov 28, 2011 at 12:37:34PM +0100, Laurent Pinchart wrote:
> >>> When mapping from a V4L2 pixel format to a media bus format in the
> >>> VIDIOC_TRY_FMT and VIDIOC_S_FMT handlers, the requested format may be
> >>> unsupported by the driver. Return a hardcoded format instead of
> >>> WARN()ing in that case.
> >>> 
> >>> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> >>> ---
> >>> 
> >>>  drivers/media/video/omap3isp/ispvideo.c |    8 ++++----
> >>>  1 files changed, 4 insertions(+), 4 deletions(-)
> >>> 
> >>> diff --git a/drivers/media/video/omap3isp/ispvideo.c
> >>> b/drivers/media/video/omap3isp/ispvideo.c index d100072..ffe7ce9 100644
> >>> --- a/drivers/media/video/omap3isp/ispvideo.c
> >>> +++ b/drivers/media/video/omap3isp/ispvideo.c
> >>> @@ -210,14 +210,14 @@ static void isp_video_pix_to_mbus(const struct
> >>> v4l2_pix_format *pix,
> >>> 
> >>>  	mbus->width = pix->width;
> >>>  	mbus->height = pix->height;
> >>> 
> >>> -	for (i = 0; i < ARRAY_SIZE(formats); ++i) {
> >>> +	/* Skip the last format in the loop so that it will be selected if 
no
> >>> +	 * match is found.
> >>> +	 */
> >>> +	for (i = 0; i < ARRAY_SIZE(formats) - 1; ++i) {
> >>> 
> >>>  		if (formats[i].pixelformat == pix->pixelformat)
> >>>  		
> >>>  			break;
> >>>  	
> >>>  	}
> >>> 
> >>> -	if (WARN_ON(i == ARRAY_SIZE(formats)))
> >>> -		return;
> >>> -
> >>> 
> >>>  	mbus->code = formats[i].code;
> >>>  	mbus->colorspace = pix->colorspace;
> >>>  	mbus->field = pix->field;
> >> 
> >> In case of setting or trying an invalid format, instead of selecting a
> >> default format, shouldn't we leave the format unchanced --- the current
> >> setting is valid after all.
> > 
> > TRY/SET operations must succeed. The format we select when an invalid
> > format is requested isn't specified. We could keep the current format,
> > but wouldn't that be more confusing for applications ? The format they
> > would get in response to a TRY/SET operation would then potentially
> > depend on the previous SET operations.
> 
> I don't think a change to something that has nothing to do what was
> requested is better than not changing it. The application has requested
> a particular format; changing it to something else isn't useful for the
> application. And if the application would try more than invalid format
> in a row, they both would yield to the same default format.
> 
> I would personally not change it.

I can agree with you for S_FMT, but I have more doubts about TRY_FMT. Making 
TRY_FMT return the current format if the requested format is not supported 
seems confusing to me. And if we make TRY_FMT return a fixed format in that 
case, why not making S_FMT do the same ? :-)

> What I can find in the spec is this:
> 
> "When the application calls the VIDIOC_S_FMT ioctl with a pointer to a
> v4l2_format structure the driver checks and adjusts the parameters
> against hardware abilities."
> 
> I wonder how other drivers behave.

uvcvideo returns -EINVAL, which I think should be fixed.

The sensor drivers I wrote return a fixed format (this isn't strictly 
S_FMT/TRY_FMT, but I think it's related).

-- 
Regards,

Laurent Pinchart

Re: [PATCH] omap3isp: video: Don't WARN() on unknown pixel formats

[Sakari Ailus]

Hi Laurent,

On Thu, Dec 01, 2011 at 12:26:07AM +0100, Laurent Pinchart wrote:
> On Wednesday 30 November 2011 09:35:38 Sakari Ailus wrote:
> > Laurent Pinchart wrote:
> > > On Monday 28 November 2011 17:01:12 Sakari Ailus wrote:
> > >> On Mon, Nov 28, 2011 at 12:37:34PM +0100, Laurent Pinchart wrote:
> > >>> When mapping from a V4L2 pixel format to a media bus format in the
> > >>> VIDIOC_TRY_FMT and VIDIOC_S_FMT handlers, the requested format may be
> > >>> unsupported by the driver. Return a hardcoded format instead of
> > >>> WARN()ing in that case.
> > >>> 
> > >>> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > >>> ---
> > >>> 
> > >>>  drivers/media/video/omap3isp/ispvideo.c |    8 ++++----
> > >>>  1 files changed, 4 insertions(+), 4 deletions(-)
> > >>> 
> > >>> diff --git a/drivers/media/video/omap3isp/ispvideo.c
> > >>> b/drivers/media/video/omap3isp/ispvideo.c index d100072..ffe7ce9 100644
> > >>> --- a/drivers/media/video/omap3isp/ispvideo.c
> > >>> +++ b/drivers/media/video/omap3isp/ispvideo.c
> > >>> @@ -210,14 +210,14 @@ static void isp_video_pix_to_mbus(const struct
> > >>> v4l2_pix_format *pix,
> > >>> 
> > >>>  	mbus->width = pix->width;
> > >>>  	mbus->height = pix->height;
> > >>> 
> > >>> -	for (i = 0; i < ARRAY_SIZE(formats); ++i) {
> > >>> +	/* Skip the last format in the loop so that it will be selected if 
> no
> > >>> +	 * match is found.
> > >>> +	 */
> > >>> +	for (i = 0; i < ARRAY_SIZE(formats) - 1; ++i) {
> > >>> 
> > >>>  		if (formats[i].pixelformat == pix->pixelformat)
> > >>>  		
> > >>>  			break;
> > >>>  	
> > >>>  	}
> > >>> 
> > >>> -	if (WARN_ON(i == ARRAY_SIZE(formats)))
> > >>> -		return;
> > >>> -
> > >>> 
> > >>>  	mbus->code = formats[i].code;
> > >>>  	mbus->colorspace = pix->colorspace;
> > >>>  	mbus->field = pix->field;
> > >> 
> > >> In case of setting or trying an invalid format, instead of selecting a
> > >> default format, shouldn't we leave the format unchanced --- the current
> > >> setting is valid after all.
> > > 
> > > TRY/SET operations must succeed. The format we select when an invalid
> > > format is requested isn't specified. We could keep the current format,
> > > but wouldn't that be more confusing for applications ? The format they
> > > would get in response to a TRY/SET operation would then potentially
> > > depend on the previous SET operations.
> > 
> > I don't think a change to something that has nothing to do what was
> > requested is better than not changing it. The application has requested
> > a particular format; changing it to something else isn't useful for the
> > application. And if the application would try more than invalid format
> > in a row, they both would yield to the same default format.
> > 
> > I would personally not change it.
> 
> I can agree with you for S_FMT, but I have more doubts about TRY_FMT. Making 
> TRY_FMT return the current format if the requested format is not supported 
> seems confusing to me. And if we make TRY_FMT return a fixed format in that 
> case, why not making S_FMT do the same ? :-)

I'd rather have it the other way around. :-)

Hans; what do you think? (Cc Hans.)

> > What I can find in the spec is this:
> > 
> > "When the application calls the VIDIOC_S_FMT ioctl with a pointer to a
> > v4l2_format structure the driver checks and adjusts the parameters
> > against hardware abilities."
> > 
> > I wonder how other drivers behave.
> 
> uvcvideo returns -EINVAL, which I think should be fixed.
> 
> The sensor drivers I wrote return a fixed format (this isn't strictly 
> S_FMT/TRY_FMT, but I think it's related).

For the mbus format it's a little bit different: if the format is something
else than what the user asked for, chances are high there's no use for it.

Cheers,

-- 
Sakari Ailus
e-mail: sakari.ailus@iki.fi	jabber/XMPP/Gmail: sailus@retiisi.org.uk

Re: [PATCH] omap3isp: video: Don't WARN() on unknown pixel formats

[Laurent Pinchart]

Hi Sakari,

On Thursday 01 December 2011 15:34:51 Sakari Ailus wrote:
> On Thu, Dec 01, 2011 at 12:26:07AM +0100, Laurent Pinchart wrote:
> > On Wednesday 30 November 2011 09:35:38 Sakari Ailus wrote:
> > > Laurent Pinchart wrote:
> > > > On Monday 28 November 2011 17:01:12 Sakari Ailus wrote:
> > > >> On Mon, Nov 28, 2011 at 12:37:34PM +0100, Laurent Pinchart wrote:
> > > >>> When mapping from a V4L2 pixel format to a media bus format in the
> > > >>> VIDIOC_TRY_FMT and VIDIOC_S_FMT handlers, the requested format may
> > > >>> be unsupported by the driver. Return a hardcoded format instead of
> > > >>> WARN()ing in that case.
> > > >>> 
> > > >>> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > > >>> ---
> > > >>> 
> > > >>>  drivers/media/video/omap3isp/ispvideo.c |    8 ++++----
> > > >>>  1 files changed, 4 insertions(+), 4 deletions(-)
> > > >>> 
> > > >>> diff --git a/drivers/media/video/omap3isp/ispvideo.c
> > > >>> b/drivers/media/video/omap3isp/ispvideo.c index d100072..ffe7ce9
> > > >>> 100644 --- a/drivers/media/video/omap3isp/ispvideo.c
> > > >>> +++ b/drivers/media/video/omap3isp/ispvideo.c
> > > >>> @@ -210,14 +210,14 @@ static void isp_video_pix_to_mbus(const
> > > >>> struct v4l2_pix_format *pix,
> > > >>> 
> > > >>>  	mbus->width = pix->width;
> > > >>>  	mbus->height = pix->height;
> > > >>> 
> > > >>> -	for (i = 0; i < ARRAY_SIZE(formats); ++i) {
> > > >>> +	/* Skip the last format in the loop so that it will be selected
> > > >>> if no
> > > >>> +	 * match is found.
> > > >>> +	 */
> > > >>> +	for (i = 0; i < ARRAY_SIZE(formats) - 1; ++i) {
> > > >>> 
> > > >>>  		if (formats[i].pixelformat == pix->pixelformat)
> > > >>>  		
> > > >>>  			break;
> > > >>>  	
> > > >>>  	}
> > > >>> 
> > > >>> -	if (WARN_ON(i == ARRAY_SIZE(formats)))
> > > >>> -		return;
> > > >>> -
> > > >>> 
> > > >>>  	mbus->code = formats[i].code;
> > > >>>  	mbus->colorspace = pix->colorspace;
> > > >>>  	mbus->field = pix->field;
> > > >> 
> > > >> In case of setting or trying an invalid format, instead of selecting
> > > >> a default format, shouldn't we leave the format unchanced --- the
> > > >> current setting is valid after all.
> > > > 
> > > > TRY/SET operations must succeed. The format we select when an invalid
> > > > format is requested isn't specified. We could keep the current
> > > > format, but wouldn't that be more confusing for applications ? The
> > > > format they would get in response to a TRY/SET operation would then
> > > > potentially depend on the previous SET operations.
> > > 
> > > I don't think a change to something that has nothing to do what was
> > > requested is better than not changing it. The application has requested
> > > a particular format; changing it to something else isn't useful for the
> > > application. And if the application would try more than invalid format
> > > in a row, they both would yield to the same default format.
> > > 
> > > I would personally not change it.
> > 
> > I can agree with you for S_FMT, but I have more doubts about TRY_FMT.
> > Making TRY_FMT return the current format if the requested format is not
> > supported seems confusing to me. And if we make TRY_FMT return a fixed
> > format in that case, why not making S_FMT do the same ? :-)
> 
> I'd rather have it the other way around. :-)

TRY_FMT means "can I use this format?". If the format isn't supported, the 
driver answers "no, you should use this other format instead". I think that 
making that other format depend on the current format would be confusing.

For S_FMT I could agree with you. When asked "please use this format", the 
driver can answer "I can't, so I'm going to use this other one instead". That 
other format could be the current one. However, it might be confusing (and 
more difficult to implement) to return different formats in TRY_FMT and 
S_FMTfor the same input. That's why I'm inclined to make S_FMT report the same 
format as TRY_FMT.

This being said, the TRY_FMT/S_FMT behaviour of the OMAP3 ISP driver is 
currently a bit broken, and ENUMFMT isn't implemented. Fixing this properly 
requires getting rid of our current multiple video queues per video node hack 
and using CREATE_BUFS instead. I'll see if I can find time to fix that. I 
would still like to integrate this patch (or something close) in the meantime 
to remove the WARN_ON.

> Hans; what do you think? (Cc Hans.)
> 
> > > What I can find in the spec is this:
> > > 
> > > "When the application calls the VIDIOC_S_FMT ioctl with a pointer to a
> > > v4l2_format structure the driver checks and adjusts the parameters
> > > against hardware abilities."
> > > 
> > > I wonder how other drivers behave.
> > 
> > uvcvideo returns -EINVAL, which I think should be fixed.
> > 
> > The sensor drivers I wrote return a fixed format (this isn't strictly
> > S_FMT/TRY_FMT, but I think it's related).
> 
> For the mbus format it's a little bit different: if the format is something
> else than what the user asked for, chances are high there's no use for it.
> 
> Cheers,

-- 
Regards,

Laurent Pinchart

Re: [PATCH] omap3isp: video: Don't WARN() on unknown pixel formats

[Sakari Ailus]

On Wed, Dec 07, 2011 at 02:44:11PM +0100, Laurent Pinchart wrote:
> Hi Sakari,

Moi,

> On Thursday 01 December 2011 15:34:51 Sakari Ailus wrote:
> > On Thu, Dec 01, 2011 at 12:26:07AM +0100, Laurent Pinchart wrote:
> > > On Wednesday 30 November 2011 09:35:38 Sakari Ailus wrote:
> > > > Laurent Pinchart wrote:
> > > > > On Monday 28 November 2011 17:01:12 Sakari Ailus wrote:
> > > > >> On Mon, Nov 28, 2011 at 12:37:34PM +0100, Laurent Pinchart wrote:
> > > > >>> When mapping from a V4L2 pixel format to a media bus format in the
> > > > >>> VIDIOC_TRY_FMT and VIDIOC_S_FMT handlers, the requested format may
> > > > >>> be unsupported by the driver. Return a hardcoded format instead of
> > > > >>> WARN()ing in that case.
> > > > >>> 
> > > > >>> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > > > >>> ---
> > > > >>> 
> > > > >>>  drivers/media/video/omap3isp/ispvideo.c |    8 ++++----
> > > > >>>  1 files changed, 4 insertions(+), 4 deletions(-)
> > > > >>> 
> > > > >>> diff --git a/drivers/media/video/omap3isp/ispvideo.c
> > > > >>> b/drivers/media/video/omap3isp/ispvideo.c index d100072..ffe7ce9
> > > > >>> 100644 --- a/drivers/media/video/omap3isp/ispvideo.c
> > > > >>> +++ b/drivers/media/video/omap3isp/ispvideo.c
> > > > >>> @@ -210,14 +210,14 @@ static void isp_video_pix_to_mbus(const
> > > > >>> struct v4l2_pix_format *pix,
> > > > >>> 
> > > > >>>  	mbus->width = pix->width;
> > > > >>>  	mbus->height = pix->height;
> > > > >>> 
> > > > >>> -	for (i = 0; i < ARRAY_SIZE(formats); ++i) {
> > > > >>> +	/* Skip the last format in the loop so that it will be selected
> > > > >>> if no
> > > > >>> +	 * match is found.
> > > > >>> +	 */
> > > > >>> +	for (i = 0; i < ARRAY_SIZE(formats) - 1; ++i) {
> > > > >>> 
> > > > >>>  		if (formats[i].pixelformat == pix->pixelformat)
> > > > >>>  		
> > > > >>>  			break;
> > > > >>>  	
> > > > >>>  	}
> > > > >>> 
> > > > >>> -	if (WARN_ON(i == ARRAY_SIZE(formats)))
> > > > >>> -		return;
> > > > >>> -
> > > > >>> 
> > > > >>>  	mbus->code = formats[i].code;
> > > > >>>  	mbus->colorspace = pix->colorspace;
> > > > >>>  	mbus->field = pix->field;
> > > > >> 
> > > > >> In case of setting or trying an invalid format, instead of selecting
> > > > >> a default format, shouldn't we leave the format unchanced --- the
> > > > >> current setting is valid after all.
> > > > > 
> > > > > TRY/SET operations must succeed. The format we select when an invalid
> > > > > format is requested isn't specified. We could keep the current
> > > > > format, but wouldn't that be more confusing for applications ? The
> > > > > format they would get in response to a TRY/SET operation would then
> > > > > potentially depend on the previous SET operations.
> > > > 
> > > > I don't think a change to something that has nothing to do what was
> > > > requested is better than not changing it. The application has requested
> > > > a particular format; changing it to something else isn't useful for the
> > > > application. And if the application would try more than invalid format
> > > > in a row, they both would yield to the same default format.
> > > > 
> > > > I would personally not change it.
> > > 
> > > I can agree with you for S_FMT, but I have more doubts about TRY_FMT.
> > > Making TRY_FMT return the current format if the requested format is not
> > > supported seems confusing to me. And if we make TRY_FMT return a fixed
> > > format in that case, why not making S_FMT do the same ? :-)
> > 
> > I'd rather have it the other way around. :-)
> 
> TRY_FMT means "can I use this format?". If the format isn't supported, the 
> driver answers "no, you should use this other format instead". I think that 
> making that other format depend on the current format would be confusing.

Also ENUM_FMT will depend on the format configured on the pipeline. If the
sensor connected to the CCDC produces YUV, the CCDC video capture node
musn't advertise YUV formats either.

I'm not saying this interface should be used by regular V4L2 applications,
but the pipeline configuration library.

> For S_FMT I could agree with you. When asked "please use this format", the 
> driver can answer "I can't, so I'm going to use this other one instead". That 
> other format could be the current one. However, it might be confusing (and 
> more difficult to implement) to return different formats in TRY_FMT and 
> S_FMTfor the same input. That's why I'm inclined to make S_FMT report the same 
> format as TRY_FMT.
> 
> This being said, the TRY_FMT/S_FMT behaviour of the OMAP3 ISP driver is 
> currently a bit broken, and ENUMFMT isn't implemented. Fixing this properly 
> requires getting rid of our current multiple video queues per video node hack 
> and using CREATE_BUFS instead. I'll see if I can find time to fix that. I 
> would still like to integrate this patch (or something close) in the meantime 
> to remove the WARN_ON.

Indeed, choosing a format, whether we agree on which one it should be or
not, is a big improvement over the current kernel warning. I reckon this is
might not reflect what the driver _should_ implement. It will take some time
to get the final answer for that, I guess. This is still one possible
solution.

So,

Acked-by: Sakari Ailus <sakari.ailus@iki.fi>

-- 
Sakari Ailus
e-mail: sakari.ailus@iki.fi	jabber/XMPP/Gmail: sailus@retiisi.org.uk