On Saturday 22 May 2010, Andy Walls wrote: > On Sat, 2010-05-22 at 15:06 +0100, Andre Draszik wrote: > > Hi, > > > > As per the spec, the above ioctl codes are defined for inputs only - > > it would be useful if there were similar codes for outputs. > > > > I therefore propose to add the following: > > > > VIDIOC_G_OUTPUT_STD > > VIDIOC_S_OUTPUT_STD > > VIDIOC_ENUM_OUTPUT_STD > > > > which would behave similar to the above, but for output devices. > > > > Thoughts? > > Currently the ivtv driver, for the PVR-350's output, uses VIDIOC_S_STD. > > >From what I see: > ivtv/ioctl.c > zoran/zoran_driver.c > davinci/vpif_display.c > > all use VIDIOC_S_STD for setting the output standard. > > Note that the v4l2_subdev video_ops have a "s_std_output" method which > is what you can grep for in the code to verify for yourself. > > > Some thoughts: > > 1. to me it appears that the ivtv driver looks like it ties the output > standard to the input standard currently (probably due to some firmware > limitation). This need not be the case in general.
The ivtv limitation is the driver and not the firmware. The firmware itself seems quite happy with mixed standards & in some cases will automatically switch the output standard itself (resulting in a standards mismatch between the cx23415 & saa7127, breaking output). For the previous 2 months I've been running a patched version of the ivtv driver that separates the input & output format with no noticeable issues. > 2. currently the ivtv driver uses sepearte device nodes for input device > and an output device. If bridge drivers maintain that paradigm, then > separate ioctl()s for S_STD, G_STD, and ENUMSTD are likely not needed. This is how my patched version works, talk to an input device for the input & an output device for the output. However, from my reading of the specs I do get the impression this is not the 'correct' way to do this and it should really be a separate ioctl. I don't know what other cards, if any, support mixed input & output standards or how they handle it. -- Ian -- 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
