On Tue, 9 Jun 2009, Mauro Carvalho Chehab wrote: > Em Tue, 9 Jun 2009 18:08:38 +0200 > Hans Verkuil <hverk...@xs4all.nl> escreveu: > > > > > > Should I submit a patch that implement VIDIOC_S_JPEGCOMP support in the > > > > UVC driver and implement a JPEG compression quality control later, or > > > > would you prefer the driver not to implement VIDIOC_S_JPEGCOMP at all ? > > > > As there are existing applications using that ioctl a few users are > > > > pushing for VIDIOC_S_JPEGCOMP support. > > > > > > I prefer the later. Adding a new ioctl support just to deprecate it on > > > the next kernel doesn't seem nice. Let's add directly the newer controls > > > and add a patch marking this as deprecated. > > > > I'm not sure whether we can deprecate JPEGCOMP. It is used in too many > > places. Perhaps we should create a set of JPEG controls that match what is > > in v4l2_jpegcompression and convert all the drivers that use JPEGCOMP to > > these new controls. Then the v4l core can map S/G_JPEGCOMP ioctls to a set > > of control read/writes. I'm working on string control support, so that will > > allow us to handle the APP_data and COM_data fields. > > This seems to be the correct approach. Implement it as controls, and let > video_ioctl2 to handle the calls to the legacy ioctls, while marking it as > deprecate.
One problem is that COM and APP segment actually have a string of bytes associated with them. Right now we only have boolean and interger controls. There is no way to set a control to the 32-bytes you want put into a APP segment. Now, if we added NUL terminated string and fixed length byte arrays as control types this could be done. I know that's something I've mentioned before. It would also be a step to allowing drivers to export metadata about captured images (exposured info, focus tracking, etc.) via a control-like interface. -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html