pvrxxx, linux code and modules

usleepless at gmail.com usleepless at gmail.com
Mon Apr 16 22:51:38 UTC 2007


On 4/16/07, John-Mark Gurney <gurney_j at resnet.uoregon.edu> wrote:
> Greg 'groggy' Lehey wrote this message on Mon, Apr 16, 2007 at 15:20 +0930:
> > - I need to understand better how tuners work.  I've been thinking of
> >   writing a document on the subject, something that people could use
> >   for help when writing drivers.  If you know of anything, even
> >   partial or badly laid out, please let me know.
> Just to reiterate, tuner code really should be located in userland..
> it's not time sensitive, and can't corrupted state of the kernel..
> As for tuners, most/all of them communicate through the i2c bus...
> The tuner is programed w/ the frequency to tune, and depending upon
> the range of frequence will turn on/off various transistors to change
> some of the analog curcuit behavior...
> My HDTV device drive does all the tuning from userland...

which driver is this?

> It was
> a lot easier to get it working using userland than having to constantly
> load/unload kernel modules, and risk crashing the machine...

you are absolutely spot on about this. it's that i did build upon
pvr250 which had the tuner in kernel space, so i didn't think about
it. otherwise i might have been influenced by the linux source, and i
would have implemented in kernel space as well :-)

but considering V4L(2), which has to support ioctl's changing the
frequency, how could this work from userland?



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