Hi Hans, Stefan, all,
On 01.02.23 10:15, Hans Verkuil wrote:
Hi Stefan, Sören,
On 01/02/2023 00:56, Stefan Herdler wrote:
Hello Hans,
I'm glad to read that at least the saa7146 driver won't be removed
completely.
On 31/01/23 09:45, Hans Verkuil wrote:
Hi Stefan,
On 30/01/2023 23:19, Stefan Herdler wrote:
Hello everyone.
This mail is a little bit long, I'm sorry for that.
But I have to describe the TV-situation in Germany roughly. Without that
knowledge it is definitely not understandable why this DVB-S cards are
still very useful here.
Reader familiar with this crazy situation may proceed to the driver
section below.
I'm primary a user of this cards but have profound knowledge about the
Hardware. I used to repair the cards for me and other users back then.
I own Fullfeatured and Budget-cards and use them daily in my VDR-System.
In Germany many channels are free-to-air in the DVB-S version only. I
would like to use these cards for a few more years until DVB-S is
deactivated or the HD-Versions of the channels become free-to-air.
I'm not willing to pay 75 Euro a year for TV-commercials in HD and I'm
not the only one with this opinion.
14 million of the 17 million satelite-tv-households in Germany watch
this channels in SD-quality only (~82%)![1]
In addition uses the encrypting-system a proprietary CAM extension which
makes it impossible to watch this channels on a HTPC legally.
This situation won't change until 2025 (by a kind of law!). What then
happens is currently completely uncertain.
The driver topic however is new to me, the cards where always working
out of the box. I noticed the upcoming removal right before my first mail.
Honestly I was a little shocked that the driver may be removed from Kernel.
Don't worry, the saa7146 driver won't be removed. I admit that that was
my initial plan, but you are not the only one who contacted me to let me
know that the DVB functionality is still in use. I had not expected that
for such old hardware, but it is clear that this driver can't be removed.
I'm glad to read this.
The card may be old and not produced any more, but they are not rare and
easily obtainable second hand. There are always multiple offers for
reasonable prices on the common platforms.
And the cards are running flawless on current mainboards with PCIe-PCI
Bridge.
There must be a lot of SAA7146 based cards been sold in Europe. Many
brands sold them, mostly rebranded Technotrend cards.
Even Hauppauge, the most important brand, sold the TT-Budged as "Nova"
and the Fullfeatured as "Nexus" for years. Their own Connexant based
designs came pretty late, short before the PCIe-cards.
I carefully estimate, at least 50% of all PCI-DVB-cards sold in Europe
where SAA7146 based.
There must be still a number of users out there.
The relevance of SAA7146 for PCI-DVB-cards is almost like the Bttv-Chips
for analog TV a few years before. At least in Europe.
And the bttv driver not deprecated despite older and using videobuf1 API!
The underlying reason for deprecating this driver in the first place was
the use of the old videobuf framework for analog TV in this driver: we
want to get rid of that, either by removing such drivers, or converting
it to vb2 (we plan to do that for bttv and cx18). For the saa7146 there
is another option: dropping the analog TV support only.
I totally agree to the vb2 conversion and would be happy to help with that.
SAA7146 driver
==============
I've read a lot in the last days and the main issue with the SAA7146
driver seems to be the missing maintainer.
All other issues seem to be a result of that.
Right?
Right. I'm on record as the maintainer, but I really don't have the time
to do a substantial job like the vb2 conversion.
As hobbyist linux developer I also have not much time for this driver
work. Nevertheless, I want to keep the DVB full-featured cards alive and
I would spend some time on that.
And the driver desperately needs someone with expertise about the cards
and the driver.
I've spotted a big chunk of unused code just by knowing which cards have
been build and which not.
Maybe we should start to remove all the unused code. With luck there is
not much left for conversion.
Sören Moch offered to maintain the complete SAA7146 driver in the
VDRportal and in this list too. This offer includes the videobuf2
conversion too.
On condition that the support of the fullfeatured cards stays in the
kernel.
I understand that. He only owns fullfeatured cards.
And I am interested in keeping my fullfeatured cards operational too.
I'm convinced Sören could handle the driver well and he is the only one
I know who probably could do that. And he is actively offering to do the
job.
Honestly, that would be great. We really need to get rid of the old videobuf
framework, it is awful. I found someone to do the bttv conversion, and I plan
to do the cx18 conversion. So that leaves the saa7146: it's either converted
to vb2, or analog video support (that's the part that uses videobuf) has to
be removed.
Obviously, if someone wants to do the vb2 conversion, then that would be
perfect. I was looking at removing analog video support, and that doesn't
look as easy as I thought it would be.
I only own full-featured (Nexus) cards, modified to also support a mode
of operation like budget cards. In full-featured cards there is a
possibility to re-read the decoded video output signal back, which could
be similar to how analog cards work. But I never had access to
analog/hybrid saa7146 cards, so I'm not sure I can test this mode. I
also don't know anybody with such card who could help testing.
I personally do not care much about analog card support in the driver,
but will at least check which part of analog functionality is used in
full-featured cards. Maybe the support for analog/hybrid cards and some
test coverage comes for free with full support for full-featured cards.
The SAA7146 driver suite is a kind of beast ;-).
I guess it is mainly caused by the DVB-C Budget-Cards.
There are some having analog support too.
I can certainly advice how to go about converting to vb2 as I've done it a
few times in the past. It's rather painful, mostly because it is a 'big bang'
change: it ends up as a single large and mostly unreviewable patch.
OK, thanks.
Indeed, I've searched for some patches and all are huge.
I have some basic C knowledge, but no experience with kerneldrivers nor
vb1 nor vb2. Unfortunately such a conversion would be out of scope for
me. At least if it should be done in a reasonable time frame.
Sören wrote the conversion would't be a big deal for him and it would be
done within a few weeks.
That leads to the DVB-API part for the AV7110 which should be removed.
An API conversion for the AV7110 does not make sense any more. 10 years
ago maybe, but not now.
Working software would be broken and there will be no benefit for the
user at all.
Converting is however not easy and a driver specific UAPI would be
necessary in any case.
The ioctl "VIDEO_SELECT_SOURCE" needed and definitely missing in the
V4l2-API (see ivtv driver).
The OSD of the FF-Cards is more canvas like, not a framebuffer. The OSD
ioctl are also needed and I haven't found anything in V4l2-API to
replace them.
What about putting the 3 API-files into one driver specific UAPI file?
The deprecated DVB-API part could be officially removed and the
maintainer of the av7110 driver would become responsible for the API.
Could that be an acceptable solution for everybody?
Or do the ~10Kb of possible redundancy in the header hurt so much?
I think this can be something that can be discussed later. It's not my
main concern and not the reason why I originally planned to remove the
driver. The use of videobuf is the main problem.
As already explained, my main concern are full-featured cards. With all
the required conversions for these cards done, also budget cards and
maybe analog/hybrid cards can be supported. If (full) analog support is
not testable, I also would take care of removing the remaining old
videobuf code.
But, all this only makes sense to me when full-featured cards and the
output part of the DVB API remain supported in mainline.
If Sören wants to become an active maintainer for this driver, then the
vb2 conversion would be the first step. But there is a lot more that can
be done, I'm sure.
Yes he wants, that is his offer to the VDR-community.
For almost 10 years I maintain the saa716x driver [1] for
high-definition full-featured cards and related budget cards. The HD-FF
cards are the successor of the saa7146 based full-featured cards, with
the same API, very similar driver structure, and same application area
(mainly VDR). It would make much sense to maintain both drivers together
in mainline. That would be a big win for everyone, users, distributors,
and developers. But yes, first step would be to get the saa7146 driver
out of staging/deprecated.
He just wants a kind of guarantee, that the driver for the fullfeatured
cards he owns stays in the kernel.
That is understandable for me, he would do the job voluntary without
been payed.
Once it is converted to vb2 the driver can stay.
So, Hans, you will also move ttpci, av7110, and the DVB output API
documentation back from staging, when all the old videobuf code is
removed? And give up the strange attitude of "Cleanup patches for the
drivers here won't be accepted." for av7110 [2]?
Note that the driver might need a bit more work: we use the v4l2-compliance
utility to test V4L2 API compliance of a driver, and after the vb2
conversion the driver should pass this test. So the compliance test might
find some other things that do not work as they should, and it would be
really good to clean that up as well. Usually the things it finds are pretty
easy to fix.
I totally agree that all available compliance tests should pass.
Most parts of the driver are implementing the DVB API, though. Probably
only for the analog parts we use v4l2. Especially for full-featured
cards the read-back of the analog output signal is more like a debug
mode (for DVB OSD applications, VDR skin plugins) and probably not
working in isolation like a fully compliant v4l2 input device. But I'm
happy to make this as compliant as possible.
There is a long lasting controversy about the deprecated 3 DVB-API-files
for the av7110 driver.
Sören stated he is tired about that discussions and looking for
permanent solution without having to rewrite the whole driver.
In this case I'm just the messenger, but I would also prefer a permanent
solution.
That is why I made the suggestion with the driver specific UAPI file.
The av7110 driver is only driver using this API-part.
And the modification is fairly easy and the impact minimal.
May that be a compromise all parties can live with?
Moving it to a public av7110.h header makes sense to me.
It's a nice-to-have in my view, and moving it to a driver-specific API
should avoid future discussions.
For me this looks it little bit different. I would like to keep all
parts of the DVB API separate, because at least 2 different drivers
(saa7146/av7110 and saa716x) are using these APIs. And again, I would be
more than happy to get saa716x upstream, so that both DVB output drivers
are in mainline. For HD full-featured cards there are most likely even
more users than for SD-FF cards.
The fact remains that as long as
people use this API we can't remove it, however much we would want to.
I think the main problem has always been that we are surprised at how
many people still use these cards. It's very similar in that respect
to the bttv driver: very old, but still in use.
The difference appears to be that the use of saa7146 cards is confined
to a specific region (esp. Germany), whereas bttv is in use worldwide.
Because of that we just miss that it is still in use.
Having an active maintainer should help with that.
I already offered several times to maintain one or preferably both
drivers in linux-media. Thanks for providing such offer now. I'm really
glad to see linux-media/DVB starting to work together with the community
like any other linux subsystem.
Regards,
Soeren
[1] https://github.com/s-moch/linux-saa716x
[2]
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/staging/media/deprecated/saa7146/av7110/TODO?h=v6.2-rc6
