[PATCH] libcamera: v4l2_videodevice: Use bufferType_ in [get|try|set]Format()

[Laurent Pinchart]

Hi Hans,

On Fri, Jul 19, 2024 at 03:07:26PM +0200, Hans de Goede wrote:
> On 7/19/24 9:37 AM, Laurent Pinchart wrote:
> > On Sat, Jul 13, 2024 at 08:43:27PM +0200, Hans de Goede wrote:
> >> V4L2VideoDevice is using the caps to determine which kind of buffers to
> >> use with the video-device in 2 different cases:
> >>
> >> 1. V4L2VideoDevice::open()
> >> 2. V4L2VideoDevice::[get|try|set]Format()
> >>
> >> And the order in which the caps are checked is different between
> >> these 2 cases. This is a problem for /dev/video# nodes which support
> >> both video-capture and metadata buffers. open() sets bufferType_ to
> >> V4L2_BUF_TYPE_VIDEO_CAPTURE[_MPLANE] in this case, where as
> >> [get|try|set]Format() will call [get|set]FormatMeta() which does not
> >> work with V4L2_BUF_TYPE_VIDEO_CAPTURE[_MPLANE] buffers.
> >>
> >> Switch [get|try|set]Format() to use the bufferType_ to determine on what
> >> sort of buffers they should be operating, leaving the V4L2VideoDevice
> >> code with only a single place where the decision is made what sort
> >> of buffers it should operate on for a specific /dev/video# node.
> >>
> >> This will also allow to modify open() in the future to take a bufferType
> >> argument to allow overriding the default bufferType it selects for
> >> /dev/video# nodes which are capable of supporting more then 1 buffer type.
> >>
> >> Signed-off-by: Hans de Goede <hdegoede at redhat.com>
> >> ---
> >>  src/libcamera/v4l2_videodevice.cpp | 56 ++++++++++++++++++++++--------
> >>  1 file changed, 41 insertions(+), 15 deletions(-)
> >>
> >> diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp
> >> index 4947aa3d..a8dc5355 100644
> >> --- a/src/libcamera/v4l2_videodevice.cpp
> >> +++ b/src/libcamera/v4l2_videodevice.cpp
> >> @@ -803,12 +803,19 @@ std::string V4L2VideoDevice::logPrefix() const
> >>   */
> >>  int V4L2VideoDevice::getFormat(V4L2DeviceFormat *format)
> >>  {
> >> -	if (caps_.isMeta())
> >> -		return getFormatMeta(format);
> >> -	else if (caps_.isMultiplanar())
> >> -		return getFormatMultiplane(format);
> >> -	else
> >> +	switch (bufferType_) {
> >> +	case V4L2_BUF_TYPE_VIDEO_CAPTURE:
> >> +	case V4L2_BUF_TYPE_VIDEO_OUTPUT:
> >>  		return getFormatSingleplane(format);
> >> +	case V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE:
> >> +	case V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE:
> >> +		return getFormatMultiplane(format);
> >> +	case V4L2_BUF_TYPE_META_CAPTURE:
> >> +	case V4L2_BUF_TYPE_META_OUTPUT:
> >> +		return getFormatMeta(format);
> >> +	default:
> >> +		return -EINVAL;
> > 
> > This can never happen, so you could fold the default vase with any of
> > the above. I suppose returning -EINVAL could help catching future errors
> > when we'll update open() to support more types.
> 
> Right I'm not a fan of just adding a default: to some existing case
> when there is no clear default existing case.
> 
> > but forget to update the
> > code here. Is that a real risk ?
> 
> Humans make mistakes so yes IMHO this is real risk and I would
> prefer to keep this bit as is.

OK.

> >> +	}
> >>  }
> >>  
> >>  /**
> >> @@ -823,12 +830,19 @@ int V4L2VideoDevice::getFormat(V4L2DeviceFormat *format)
> >>   */
> >>  int V4L2VideoDevice::tryFormat(V4L2DeviceFormat *format)
> >>  {
> >> -	if (caps_.isMeta())
> >> -		return trySetFormatMeta(format, false);
> >> -	else if (caps_.isMultiplanar())
> >> -		return trySetFormatMultiplane(format, false);
> >> -	else
> >> +	switch (bufferType_) {
> >> +	case V4L2_BUF_TYPE_VIDEO_CAPTURE:
> >> +	case V4L2_BUF_TYPE_VIDEO_OUTPUT:
> >>  		return trySetFormatSingleplane(format, false);
> >> +	case V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE:
> >> +	case V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE:
> >> +		return trySetFormatMultiplane(format, false);
> >> +	case V4L2_BUF_TYPE_META_CAPTURE:
> >> +	case V4L2_BUF_TYPE_META_OUTPUT:
> >> +		return trySetFormatMeta(format, false);
> >> +	default:
> >> +		return -EINVAL;
> > 
> > Same here.
> > 
> >> +	}
> >>  }
> >>  
> >>  /**
> >> @@ -843,12 +857,24 @@ int V4L2VideoDevice::tryFormat(V4L2DeviceFormat *format)
> >>  int V4L2VideoDevice::setFormat(V4L2DeviceFormat *format)
> >>  {
> >>  	int ret = 0;
> > 
> > While at it you can drop the initialization of the ret variable.
> 
> Ack.
> 
> >> -	if (caps_.isMeta())
> >> -		ret = trySetFormatMeta(format, true);
> >> -	else if (caps_.isMultiplanar())
> >> -		ret = trySetFormatMultiplane(format, true);
> >> -	else
> >> +
> >> +	switch (bufferType_) {
> >> +	case V4L2_BUF_TYPE_VIDEO_CAPTURE:
> >> +	case V4L2_BUF_TYPE_VIDEO_OUTPUT:
> >>  		ret = trySetFormatSingleplane(format, true);
> >> +		break;
> >> +	case V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE:
> >> +	case V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE:
> >> +		ret = trySetFormatMultiplane(format, true);
> >> +		break;
> >> +	case V4L2_BUF_TYPE_META_CAPTURE:
> >> +	case V4L2_BUF_TYPE_META_OUTPUT:
> >> +		ret = trySetFormatMeta(format, true);
> >> +		break;
> >> +	default:
> >> +		ret = -EINVAL;
> >> +		break;
> > 
> > And here.
> > 
> > If you think we should drop the default case, please send a new version.
> > Otherwise I can drop the initialization of ret when applying. Either
> > way,
> 
> As mendtioned above I prefer to keep the default case. If you can
> drop the initialization of ret while applying this that would be
> great.
> 
> > Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> 
> Thanks & Regsrds,

Pushed. Unless I'm mistaken, initial IPU6 support is now fully merged.

> >>  
> >>  	/* Cache the set format on success. */
> >>  	if (ret)

-- 
Regards,

Laurent Pinchart