pvrxxx, linux code and modules

[usleepless at gmail.com]

John-Mark,

On 4/17/07, John-Mark Gurney <gurney_j at resnet.uoregon.edu> wrote:
> usleepless at gmail.com wrote this message on Tue, Apr 17, 2007 at 00:51 +0200:
> > 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?
>
> The DViCO FusionHDTV 5 Lite driver:
> http://www.freebsd.org/news/status/report-2006-10-2006-12.html#Bt878-Audio-Driver-(aka-FusionHDTV-5-Lite-driver)
>
> I have two tuners working in my system at home.

how does one build this driver? where can i fetch it?

> > >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?
>
> Kill the V4L(2) API? :)  I have thought about doing a cdev bridge to
> userland..  Effectively FUSE, but for cdev's instead of file systems...
> This would put most/all the logic in userland, and w/ some mmapping
> magic, can have similar/same performance for high speed devices like
> bktr...

well, i am certainly not gonna kill the v4l(2) API since i intend to
use the pvrxxx cards with mythtv.

regards,

usleep