On Wednesday, February 09, 2011 20:00:38 Matt Turner wrote: > On Wed, Feb 9, 2011 at 7:12 AM, Alex Deucher <alexdeucher@xxxxxxxxx> wrote: > > On Tue, Feb 8, 2011 at 5:47 PM, Andy Walls <awalls@xxxxxxxxxxxxxxxx> wrote: > >> On Tue, 2011-02-08 at 10:28 -0500, Alex Deucher wrote: > >>> On Tue, Feb 8, 2011 at 4:47 AM, Hans Verkuil <hansverk@xxxxxxxxx> wrote: > >>> > Just two quick notes. I'll try to do a full review this weekend. > >>> > > >>> > On Tuesday, February 08, 2011 10:30:22 Tomasz Stanislawski wrote: > >>> >> ============== > >>> >> Introduction > >>> >> ============== > >>> >> > >>> >> The purpose of this RFC is to discuss the driver for a TV output interface > >>> >> available in upcoming Samsung SoC. The HW is able to generate digital and > >>> >> analog signals. Current version of the driver supports only digital output. > >>> >> > >>> >> Internally the driver uses videobuf2 framework, and CMA memory allocator. > >>> > Not > >>> >> all of them are merged by now, but I decided to post the sources to start > >>> >> discussion driver's design. > >> > >>> > > >>> > Cisco (i.e. a few colleagues and myself) are working on this. We hope to post > >>> > an RFC by the end of this month. We also have a proposal for CEC support in > >>> > the pipeline. > >>> > >>> Any reason to not use the drm kms APIs for modesetting, display > >>> configuration, and hotplug support? We already have the > >>> infrastructure in place for complex display configurations and > >>> generating events for hotplug interrupts. It would seem to make more > >>> sense to me to fix any deficiencies in the KMS APIs than to spin a new > >>> API. Things like CEC would be a natural fit since a lot of desktop > >>> GPUs support hdmi audio/3d/etc. and are already using kms. > >>> > >>> Alex > >> > >> I'll toss one out: lack of API documentation for driver or application > >> developers to use. > >> > >> > >> When I last looked at converting ivtvfb to use DRM, KMS, TTM, etc. (to > >> possibly get rid of reliance on the ivtv X video driver > >> http://dl.ivtvdriver.org/xf86-video-ivtv/ ), I found the documentation > >> was really sparse. > >> > >> DRM had the most documentation under Documentation/DocBook/drm.tmpl, but > >> the userland API wasn't fleshed out. GEM was talked about a bit in > >> there as well, IIRC. > >> > >> TTM documentation was essentially non-existant. > >> > >> I can't find any KMS documentation either. > >> > >> I recall having to read much of the drm code, and having to look at the > >> radeon driver, just to tease out what the DRM ioctls needed to do. > >> > >> Am I missing a Documentation source for the APIs? > > Yes, > > My summer of code project's purpose was to create something of a > tutorial for writing a KMS driver. The code, split out into something > like 15 step-by-step patches, and accompanying documentation are > available from Google's website. > > http://code.google.com/p/google-summer-of-code-2010-xorg/downloads/detail?name=Matt_Turner.tar.gz Nice! What I still don't understand is if and how this is controlled via userspace. Is there some documentation of the userspace API somewhere? > My repository (doesn't include the documentation) is available here: > http://git.kernel.org/?p=linux/kernel/git/mattst88/glint.git;a=summary > > There's a 'rebased' branch that contains API changes required for the > code to work with 2.6.37~. > > I hope it's useful to you. > > I can't image how the lack of documentation of an used and tested API > could be a serious reason to write you own. That never was the main reason. It doesn't help, though. > That makes absolutely no > sense to me, so I hope you'll decide to use KMS. No, we won't. A GPU driver != a V4L driver. The primary purpose of a V4L2 display driver is to output discrete frames from memory to some device. This may be a HDMI transmitter, a SDTV transmitter, a memory-to-memory codec, an FPGA, whatever. In other words, there is not necessarily a monitor on the other end. We have for some time now V4L2 APIs to set up video formats. The original ioctl was VIDIOC_G/S_STD to select PAL/NTSC/SECAM. The new ones are VIDIOC_G/S_DV_PRESETS which set up standard formats (1080p60, 720p60, etc) and DV_TIMINGS which can be used for custom bt.656/1120 digital video timings. Trying to mix KMS into the V4L2 API is just a recipe for disaster. Just think about what it would mean for DRM if DRM would use the V4L2 API for setting video modes. That would be a disaster as well. Regards, Hans -- Hans Verkuil - video4linux developer - sponsored by Cisco -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
