On Fri, Nov 25, 2011 at 8:52 PM, Hans Verkuil <hverkuil@xxxxxxxxx> wrote: > 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). How will you handle CI+ ? The CI+ descrambler is tightly married to the DVB decoder. So you will move the CA API also to V4L, eventually ? -- 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
