[pvrusb2] Driver status [was:CPU Run pvrusb2-context]

[Mike Isely]

On Fri, 15 Oct 2010, JE Geiger wrote:

> 2.6.36 is not finalized, but I did pull down 2.6.35.7 from kernel.org
> and compiled.
> 
> The module pvrusb2 modprobes and rmmods just fine without doing the
> isely.net snapshot module compile.
> 
> HVR-1950 device performs capture fine.
> 
> Does the FM radio front end in the HVR-1950 work with pvrusb2?  I
> recall some posts from the past indicating that the FM radio was not
> functional.

No, it's not there.  The reason is not simple.

Unlike previous tuners, in the case of the HVR-1950 support of FM 
requires:

1. A specific firmware load for the cx25840 driver

2. Some kind of special mode switch issued to the cx25840 driver in 
order to enable FM reception, i.e. "enable mode XYZ because we're on an 
HVR-1950/HVR-1900 tuner".

3. Last I checked, the V4L internal API lacks the needed capability for 
issuing any kind of mode switch like this to the cx25840 module - 
because until now such a thing was never needed.

I know that Mike Krufky has done work to prove in the capability for FM 
support but he did it by hardcoding the required cx25840 mode switch - 
in other words his changes would break every other use of the cx25840 
driver.  Getting past this requires internal V4L changes.  Plus there's 
no mechanism in V4L to identify cx25840 firmware blob versions so any 
changes to the cx25840 module to support this mode also has to depend on 
specific firmware which we can't even confirm has been loaded into the 
hardware (so at the very least if the wrong firmware is present we need 
to ensure that setting that mode results in benign misbehavior).

Notice how unfortunately almost none of this actually has to do with the 
pvrusb2 driver itself.  Enabling this on the pvrusb2 side is literally a 
single bit change in pvrusb2-devattr.c.  Well and maybe a few snippets 
to enable that cx25840 mode setting once it becomes possible to actually 
do such a thing in V4L.

Sigh :-(

  -Mike


-- 

Mike Isely
isely @ isely (dot) net
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