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Date:      Tue, 17 Apr 2007 00:51:37 +0200
From:      usleepless@gmail.com
To:        "John-Mark Gurney" <gurney_j@resnet.uoregon.edu>,  "Greg 'groggy' Lehey" <grog@freebsd.org>, usleepless@gmail.com,  freebsd-multimedia@freebsd.org
Subject:   Re: pvrxxx, linux code and modules
Message-ID:  <c39ec84c0704161551i29914e70vd78f725f765c0c04@mail.gmail.com>
In-Reply-To: <20070416212605.GV73385@funkthat.com>
References:  <c39ec84c0704151508t126cf975gaa1957b9205d3244@mail.gmail.com> <20070416055055.GC1593@wantadilla.lemis.com> <20070416212605.GV73385@funkthat.com>

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John,

On 4/16/07, John-Mark Gurney <gurney_j@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?

regards,

usleep



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