I2C regression in post 2.6.14 gits..

I2C regression in post 2.6.14 gits..

[Matti Aarnio]

Specifically,  BTTV driver fails to control internal
I2C devices in Hauppauge WinTV card with Bt848 onboard.

Baseline 2.6.14 works fine,  but 2.6.14-git2 fails.

Comparing kernel messages in between respective running
kernel versions with respect to bttv driver messages
I don't see really obvious differences at all.
Nevertheless it fails to activate correct input.

There are apparently also some changes in video
input driver, but nothing that plainly shows to
be related with this particular issue. (bttv / bt84x)

Any ideas ?  Possible fixes ?

  /Matti Aarnio

Re: I2C regression in post 2.6.14 gits..

[Jean Delvare]

Hi Matti,

On 2005-11-04, Matti Aarnio wrote:
> Specifically,  BTTV driver fails to control internal
> I2C devices in Hauppauge WinTV card with Bt848 onboard.

Can you detail how you came up with this diagnosis?

> Baseline 2.6.14 works fine,  but 2.6.14-git2 fails.

Can you please try 2.6.14-git1 and 2.6.14-rc5-mm1? This should help us
norrow the faulty patch. Also, please confirm that 2.6.14-git7 still has
the problem.

> Any ideas ?  Possible fixes ?

Enable as many debugging as possible, in particular I2C Core debugging
(I2C_DEBUG_CORE=y) in a working kernel and a non-working kernel, and
send both logs for comparison.

Thanks a lot for testing, BTW.

--
Jean Delvare

Re: I2C regression in post 2.6.14 gits.. -- get_user_pages() is real bug..

[Matti Aarnio]

On Fri, Nov 04, 2005 at 10:29:34AM +0100, Jean Delvare wrote:
> Hi Matti,
> 
> On 2005-11-04, Matti Aarnio wrote:
> > Specifically,  BTTV driver fails to control internal
> > I2C devices in Hauppauge WinTV card with Bt848 onboard.
> 
> Can you detail how you came up with this diagnosis?
> 
> > Baseline 2.6.14 works fine,  but 2.6.14-git2 fails.
> 
> Can you please try 2.6.14-git1 and 2.6.14-rc5-mm1? This should help us
> norrow the faulty patch. Also, please confirm that 2.6.14-git7 still has
> the problem.
> 
> > Any ideas ?  Possible fixes ?
> 
> Enable as many debugging as possible, in particular I2C Core debugging
> (I2C_DEBUG_CORE=y) in a working kernel and a non-working kernel, and
> send both logs for comparison.
> 
> Thanks a lot for testing, BTW.


Since then I have been tracking of what really fails in the bttv driver,
and running:   strace -o tvtime.log tvtime
Result is most revealing in failures.

The fault is not in I2C, but appears in   video_buf  module failing
calls of   get_user_pages()   with  -EFAULT.

There has been lots of discussion about it back in August, but apparently
only now in post 2.6.14 the changes made it into   mm/memory.c  which
faulted this thing for BTTV. 


Oh yes,  I do use Fedora Core development kernels, and don't usually
(anymore) compile things myself, but now I had a weekend off...


> --
> Jean Delvare

/Matti Aarnio