Em 25-11-2011 13:22, Hans Verkuil escreveu: > On Friday, November 25, 2011 14:48:02 Mauro Carvalho Chehab wrote: >> Em 25-11-2011 10:00, Andreas Oberritter escreveu: >>> On 24.11.2011 19:47, Mauro Carvalho Chehab wrote: >>>> Em 24-11-2011 16:13, Manu Abraham escreveu: >>>>> On Thu, Nov 24, 2011 at 11:38 PM, Mauro Carvalho Chehab >>>>> <mchehab@xxxxxxxxxx> wrote: >>>>>> Em 24-11-2011 16:01, Manu Abraham escreveu: >>>>>>> On Thu, Nov 24, 2011 at 11:14 PM, Hans Verkuil <hverkuil@xxxxxxxxx> wrote: >>>>>>>> On Thursday, November 24, 2011 18:08:05 Andreas Oberritter wrote: >>>>>>>>> Don't break existing Userspace APIs for no reason! It's OK to add the >>>>>>>>> new API, but - pretty please - don't just blindly remove audio.h and >>>>>>>>> video.h. They are in use since many years by av7110, out-of-tree drivers >>>>>>>>> *and more importantly* by applications. Yes, I know, you'd like to see >>>>>>>>> those out-of-tree drivers merged, but it isn't possible for many >>>>>>>>> reasons. And even if they were merged, you'd say "Port them and your >>>>>>>>> apps to V4L". No! That's not an option. >>>>>>>> >>>>>>>> I'm not breaking anything. All apps will still work. >>>>>>>> >>>>>>>> One option (and it depends on whether people like it or not) is to have >>>>>>>> audio.h, video.h and osd.h just include av7110.h and add a #warning >>>>>>>> that these headers need to be replaced by the new av7110.h. >>>>>>> >>>>>>> >>>>>>> That won't work with other non av7110 hardware. >>>>>> >>>>>> There isn't any non-av7110 driver using it at the Kernel. Anyway, we can put >>>>>> a warning at the existing headers as-is, for now, putting them to be removed >>>>>> for a new kernel version, like 3.4. >>>>> >>>>> >>>>> No, that's not an option. The to-be merged saa716x driver depends on it. >>>> >>>> If the driver is not merged yet, it can be changed. >>>> >>>>> A DVB alone device need not depend V4L2 for it's operation. >>>> >>>> Why not? DVB drivers with IR should implement the input/event/IR API. DVB drivers with net >>>> should implement the Linux Network API. >>> >>> DVB doesn't specify IR. There's no such thing like a DVB IR device. >>> >>> IP over DVB is implemented transparently. No driver needs to do anything >>> but register its device's MAC address, therefore no driver implements >>> the Linux Network API. >>> >>>> There is nothing wrong on using the ALSA API for audio and the V4L2 API for video, >>>> as both API fits the needs for decoding audio and video streams, and new features >>>> could be added there when needed. >>> >>> Yes. There's nothing wrong with it and I'm not complaining. I don't care >>> about the implementation of the API in ivtv either. Just don't remove >>> the API from dvb-core, period. >>> >>>> Duplicated API's that become legacy are removed with time. Just to mention two >>>> notable cases, this happened with the old audio stack (OSS), with the old Wireless >>>> stack. >>> >>> I can still use iwconfig and linux/wireless.h is still available on my >>> system. >> >> Yes, but both iwconfig and the API changed. >> >>> ALSA still provides OSS emulation and the real OSS stack was marked >>> deprecated but still present for ages. >> >> OSS driver submission stopped years ago. I remember it clearly as they denied cx88-oss >> driver submission (2004 or 2005). The saa7134-oss and bttv-oss drivers were dropped in 2007[1] >> in favor of the alsa drivers. The only hardware that are still there at OSS are the >> legacy ones that probably no alsa developer has anymore. >> >> [1] http://kerneltrap.org/mailarchive/linux-kernel/2007/11/9/398438/thread >> >>> In contrast, you want to remove a >>> stable API and introduce a new *completely untested* API between 3.3 and >>> 3.4. >> >> Please read the patches again. The API for the devices are still there: >> any binary compiled for older kernels will still work with av7110 and ivtv. >> With the patches applied, the only difference is that the header file has >> renamed, as they were moved to device-specific headers. >> >> It should be noticed that, while both av7110 and ivtv uses the same ioctl's, av7110 >> creates devices over /dev/dvb, while ivtv uses it over /dev/video?. So, in practice, >> each driver has a different API. >> >> There are no plans to remove the API for av7110. >> >> As discussed on this thread, it seems that the agreed plans for the ivtv API is to put >> it into the standard kernel procedure to get rid of legacy API. That means that the API >> will be there for a few kernel versions. >> >> Hans proposal is to remove the ivtv API on 3.8, with seems reasonable. So, the first >> API removal will happen in about 18 months from now (assuming about 2 months per kernel >> version). >> >>>> Do you have any issues that needs to be addressed by the V4L2 API for it to fit >>>> on your needs? >>> >>> I don't want to be forced to use the V4L2 API for no reason and no gain. >> >> As already explained on the other email, there are gains on using it, like the support >> for other types of encoding, the pipeline setup, sub-device control, shared buffer interface >> with GPU, proper support for SoC, etc. >> >> Also, currently, just one device uses it (av7110). I don't think that the chipset is >> still manufactured. At least Google didn't help finding anything: >> http://www.google.com/search?q=av7110&tbm=shop&hl=en >> >> On the other hand, there are thousands of devices using V4L2 API. >> >> As both API's provide support for decoded video, one API has to be deprecated in favor >> to the other. We should select for deprecation the one that is more restrictive >> and that has just one driver using it. >> >>> >>>>> Also, it doesn't >>>>> make any sense to have device specific headers to be used by an application, >>>>> when drivers share more than one commonality. >>>> >>>> The only in-kernel driver using audio/video/osd is av7110. >>> >>> Once again: Manu is going to submit a new driver soon. >> >> The API is there for several years (since 2002?), with just one driver supporting it. >> It shouldn't be hard to convert Manu's work to the V4L2. I can help him on converting >> his driver to use the V4L2 API if needed. >> >>> You're trying to remove an API that you've never used. The people who >>> use the API want it to stay. >> >> As I said, it will stay there. Nobody will remove av7110 or remove the old API from it. >> >> The idea is that no new driver should use it, as it is a legacy one-driver-only API. >> >> If your complain is about the removal of audio.h, video.h and osd.h, then my proposal is >> to keep it there, writing a text that they are part of a deprecated API, but keeping >> the rest of the patches and not accepting anymore any submission using them, removing >> the ioctl's that aren't used by av7110 from them. > > I have no problem with that. Something along those lines was my initial idea anyway, > but I forgot about it. > > I've taken a quick look at Manu's driver: it uses very few ioctls from audio.h and > video.h and it seems that that driver uses the video device as a classic video output > device able to handle compressed video (I presume an elementary video stream). > > Using V4L for the video part is easy. But where it becomes a bit more complicated is > with the audio device. I assume again that it receives a compressed audio stream > (is that correct?), and alsa doesn't handle that yet. I believe Samsung ran into the > same issue. For raw audio an alsa output is the logical choice, but for compressed > audio it is not so clear. Sure that alsa doesn't handle compressed audio? a quick grep for MPEG under drivers/sound shows several things related to MPEG audio support: $ git grep -i mpeg sound|wc -l 92 $ git grep -i mpeg sound ... sound/core/pcm.c: FORMAT(MPEG), sound/core/pcm.c: case AFMT_MPEG: sound/core/pcm.c: return "MPEG"; sound/core/pcm_misc.c: [SNDRV_PCM_FORMAT_MPEG] = { sound/drivers/vx/vx_cmd.h:#define MASK_VALID_PIPE_MPEG_PARAM 0x000040 sound/drivers/vx/vx_cmd.h:#define MASK_SET_PIPE_MPEG_PARAM 0x000002 sound/drivers/vx/vx_cmd.h:#define P_PREPARE_FOR_MPEG3_MASK 0x02 sound/drivers/vx/vx_core.c: if (chip->audio_info & VX_AUDIO_INFO_MPEG1) sound/drivers/vx/vx_core.c: snd_iprintf(buffer, " mpeg1"); sound/drivers/vx/vx_core.c: if (chip->audio_info & VX_AUDIO_INFO_MPEG2) sound/drivers/vx/vx_core.c: snd_iprintf(buffer, " mpeg2"); ... So, I think that alsa accepts compressed audio. > BTW, how does the OSD part work on saa716x? The only supported ioctl just gives data > to the chip, but it's not clear to me how that data should be interpreted. Pointers > are welcome. > > The big picture that we should look at is that there are too many subsystems > involved in video output: drm, fbdev, v4l, and also dvb. Since there are only two > in-kernel drivers that use it, and one of those (ivtv) is easy to convert to a V4L > API, it makes sense to limit that API to just the remaining driver (av7110). > > I hope and expect that we will have opportunities next year to talk to the > other subsystems (drm in particular) to improve cooperation and code sharing > between us. > > With the ever increasing impact of SoCs in particular it is important to work > on that. This patch series is one (small) part of that. > > Regards, > > Hans > -- > 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 -- 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
