Re: RFC: Phase 2/3: Move the compat code into v4l1-compat. Convert apps.

[Chicken Shack <chicken.shack@gmx.de>]

Am Samstag, den 20.03.2010, 13:37 +0100 schrieb Hans Verkuil:
> On Saturday 20 March 2010 13:17:15 Chicken Shack wrote:
> > Am Samstag, den 20.03.2010, 10:21 +0100 schrieb Hans Verkuil:
> > > Hi all!
> > > 
> > > The second phase that needs to be done to remove the v4l1 support from the
> > > kernel is that libv4l1 should replace the v4l1-compat code from the kernel.
> > > 
> > > I do not know how complete the libv4l1 code is right now. I would like to
> > > know in particular whether the VIDIOCGMBUF/mmap behavior can be faked in
> > > libv4l1 if drivers do not support the cgmbuf vidioc call.
> > > 
> > > In principle libv4l1 should allow V4L1 apps to run fine with V4L2 drivers.
> > > That will also solve the problem of embedded device vendors running new
> > > kernels with old V4L1 applications. They just need to use libv4l1.
> > > 
> > > The third phase that can be done in parallel is to convert V4L1-only apps.
> > > I strongly suspect that any apps that are V4L1-only are also unmaintained.
> > > We have discussed before that we should set up git repositories for such
> > > tools (xawtv being one of the more prominent apps since it contains several
> > > v4l1-only console apps). Once we have maintainership, then we can convert
> > > these tools to v4l2 and distros and other interested parties have a place
> > > to send patches to.
> > > 
> > > I'm afraid that it is unlikely that anyone will do that work for us, so it's
> > > probably best just to bite the bullet and do it ourselves.
> > > 
> > > Regards,
> > > 
> > > 	Hans
> > > 
> > 
> > Hello Hans,
> > 
> > I haven't followed your discussion so far (sorry!).
> > I got a trivial question:
> > 
> > I run a Miro PCTV pro (stereo) on one of my machines.
> > It needs "simple tuner transport" / "TDA 9885/6/7 analog IF
> > demodulator", Micronas msp3400 for Stereo tone PLUS v4l1 compat layer as
> > kernel options to run / to be usable at all.
> 
> That's the V4L2 bttv driver. What app are you using with this card?

Should rather be:
What apps are you using (Plural mode)?

One big mess somehow.

1. The only one that runs is tvtime. But with tvtime I cannot record
streams.
2. Then I have tested zapping, which is a gnome app.
No matter if I start it without parameters or with parameter
LD_PRELOAD=/usr/lib/libv4l/v4l1compat.so (it's a Debian system), channel
switching is simply impossible. Version is 0.10cvs6.

Well, and the biggest pest are the radio apps:
1. Running gnomeradio the channel scanner does not find anything and I
cannot hear anything (independent from starting mode - with or without
parameters).

2. Maybe Gerd's "radio" solves it, but in that case recording is
unclear, as it is a rather primitive GUI without recording function
implied.

> > 
> > Can you make sure that this card will still be usable after your v4l1
> > removal activities are finished?
> 
> You can easily test this by turning off the compat layer in the kernel
> config. You should still be able to use your v4l1 app by using LD_PRELOAD=/usr/lib/v4l1compat.so.

Hmmm. See above. If I used the parametry in a wrong way please tell me.
 
> > In other words: What happens to this v4l1 compat code which is obviously
> > necessary for this (and other) card(s) to run?
> > 
> > That's it what I haven't understood right now, so could you please be
> > kind enough to explain that with a couple of words?
> > 
> > Thanks!
> > 
> > CS
> > 
> > P. S.: If you make your decision to host xawtv and other apps please do
> > not merge hybrid applications (i. e. apps made for DVB and analogue
> > devices) as you can find them in the xawtv 4.0 pre alpha code for
> > example in analogue trees.
> > Rather establish extra trees for hybrid applications please.
> 
> These apps will each get their own tree.
> 
> Regards,
> 
> 	Hans

This sounds excellent :)

Best Regards

Uwe

P. S.: So if I take you right the kernel compat module function does not
hit or point to the driver itself, but rather to the application layer?
Not easy to anticipate this as a picture in my head......