Re: stable regression: tda18271_read_regs: [1-0060|M] ERROR: i2c_transferreturned: -19

[Antti Palosaari]

Off-topic, Cc:s dropped, related to DVB / V4L2 tuner communication problems.

On 17.12.2013 07:39, Devin Heitmueller wrote:
> Hi Connor,
>
> On Tue, Dec 17, 2013 at 12:28 AM, Connor Behan <connor.behan@xxxxxxxxx> wrote:
> > Thanks for the detailed answer. I have tried your patch and updated the
> > wiki page. Would a 950 or 950Q be safer to buy next time?
>
> The 950 has long since been obsoleted.  You cannot buy them anymore.
> The 950q though is well supported and doesn't have this issue as it
> uses a different chip.
>
> > On 14/12/13 05:17 PM, Devin Heitmueller wrote:
> > > I had a patch kicking around which fixed part of the issue, but it
> > > didn't completely work because of the lgdt3305 having AGC enabled at
> > > chip powerup (which interferes with analog tuning on the shared
> > > tuner), and the internal v4l-dvb APIs don't provide any easy way to
> > > reset the AGC from the analog side of the device.
> >
> > By this do you mean that the functions exist but they aren't part of the
> > public API? Maybe this problem can be addressed if there is ever "v4l3"
> > or some other reason to break compatibility.
>
> No, these are internal APIs that dictate how the various driver
> components talk to each other.  Because the V4L and DVB subsystems
> were developed independently of each other, they do a really crappy
> job of communicating between them (a problem which manifests itself in
> particular when sharing hardware resources such as tuners).
>
> The problem *can* be fixed, but it would likely require
> extensions/changes to the basic frameworks used to communicate between
> the different drivers.

That shared DVB / V4L2 tuner is one problem that I have also currently 
(SDR is on V4L2 API and DTV is provided via DVB API). I have decided to 
try model where I separate RF tuner totally independent used DVB / V4L2 
APIs, just to plain I2C driver model. Idea is here to provide needed set 
of general callbacks and communication and device binding is done via 
I2C driver model.
I am not sure though if there is any big caveats I haven't realized yet...

regards
Antti

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