[pvrusb2] Problems Tuning Digital Channels on HVR-1950

[Mike Isely]

On Mon, 24 Nov 2008, Michael Krufky wrote:

   [...]

> 
> I've been meaning to respond to this all day long, but I've been short
> on spare time.  I will keep this short and sweet.
> 
> I did a diff comparison between the code in the ubuntu-intrepid kernel
> versus the code in the v4l-dvb tree.  The following is a description
> of the changes of the major components that have to do with the ATSC /
> QAM tuner components in the HVR1950:
> 
> 1) TDA18271 -- no change (other than some compat code and the removal
> of a no-op break statement)
> 
> 2) S5H1411 -- very small changes.  I looked these over with the author
> of the driver and we do not believe these to be causing the issue, but
> anything is possible.
> 
> 3) PVRUSB2 -- some larger changes that I cannot review or describe
> fairly given the lack of time that I have for this.

   [...]

I just skimmed the diff rather quickly.

The vast majority of the changes are what one would expect when 
transforming the source code for a driver from the v4l-dvb repository 
into the Linux kernel, e.g. stripping out various "if 0" bits, removing 
kernel-version-specific sections, getting rid of compat.h, etc.  Every 
driver in v4l-dvb has changes like these and they are all known to be 
safe of course.  The transformation is mechanical in nature; it is done 
via a script by the v4l-dvb maintainer when pushing changes up to the 
kernel tree.

Of the remaining changes, nearly all have to do with adding cropping 
support, which is in v4l-dvb but (not surprisingly) won't be in 2.6.27.y 
since that's a feature addition that appeared long after the 2.6.27 
merge window closed.  Beyond that, there are a few other minor bits to 
help with overall functional stability (e.g. avoid an oops if the driver 
is attempted to be associated with a device ID that it doesn't know 
about, something that can only happen if an alien device ID is forced 
into the driver at run-time).

None of the changes however have anything to do with tuning.

I'm not trying to "point the finger" here.  Allow me to explain (and 
feel free to tell me where I went astray)...  Until this reply I thought 
I had understood the situation: Back in the early 2.6.27.y releases 
(over a month ago), there was apparently a problem which impacted the 
ability to do digital tuning on the HVR-1950 - exactly the problem 
described in this thread.  The root cause had to do with some issues 
with the underlying tuner driver for the HVR-1950's tuner, not the 
pvrusb2 driver itself.  Mike Krufky and I talked about that at the time, 
and it just so happens that Steve Toth just the previous day had 
committed tuner fixes into v4l-dvb that radically improved this 
situation.  I have since confirmed that v4l-dvb is fine in this regard 
for the HVR-1950 - without any related pvrusb fixes needed.  Obviously 
those changes weren't in any mainline kernel then.  Since that time I 
believe the tuner fixes have indeed gotten into 2.6.27.y and probably 
also 2.6.26.y (but I haven't personally tested that at this point).  So 
AFAIK, there is nothing wrong with 2.6.27.y - at least with respect to 
the pvrusb2 driver or anything it depends upon.

After seeing roccomoretti's reply, I interpreted that to mean that the 
fixes hadn't made their way into the Ubuntu kernel yet.  But now with 
Mike's comparison between the Ubuntu sources and v4l-dvb I'm a little 
confused.  Are you sure roccomoretti that you were running the kernel 
version that Mike just compared?

I don't run Ubuntu here, so I do not know what "2.6.27-7" corresponds 
with.  That *could* correspond to vanilla kernel 2.6.27.7, but I don't 
really know.  (In Debian this would definitely not be the case.)

It might be a good experiment to grab vanilla kernel 2.6.27.7 from 
kernel.org, build that, and see if the tuning problem shows up again.  
If so, then we can compare the vanilla kernel tree with v4l-dvb and 
eliminate another source of uncertainty.

  -Mike


-- 

Mike Isely
isely @ pobox (dot) com
PGP: 03 54 43 4D 75 E5 CC 92 71 16 01 E2 B5 F5 C1 E8