[linux-dvb] [PATCH] add device node locking possibility to dvbcore

Markus Rechberger mrechberger at gmail.com
Thu Aug 9 18:55:43 CEST 2007


On 8/9/07, Steven Toth <stoth at hauppauge.com> wrote:
> Markus Rechberger wrote:
> > Following patch adds a rather primitive way to temporary lock dvb
> > devicenodes, this can be useful for hybrid devices which use the
> > video4linux framework for the analogue TV part and the dvb framework for
> > digital TV if only one mode can be accessed at a time.
> >
> > Signed-off-by: Markus Rechberger <markus.rechberger at amd.com>
> >
> >
> Call me dumb but I don't understand how this patch helps v4l devices. :)
>
> Allocation/management of a single card resource doesn't belong inside
> the dvb framework, these answers need to come from the bridge-frameworks
> (via callbacks from dvb-core or the analog equivalent) who are better
> placed to make the decision about hybrid tuners, bus capacity or
> allocation, in use devices.
>
> As a working example, I added similar support in my older HVR3000 tree
> where two frontends share a single transport bus. The code is old but it
> demonstrates a solution, much the my earlier patches for shared
> DVB/Blackbird boards also.
>
> I understand how this patch helps the current dvb tree, it stops
> multiple people opening a device but that's it. ... Or, maybe I've just
> missed to point.
>

Hi Steve,

the bridge framework triggers locking these filehandles.
http://mcentral.de/hg/~mrec/v4l-dvb-experimental/file/c0817d73a2a9/linux/drivers/media/video/em28xx/em28xx-video.c

line 434
this locks the dvb nodes if someone tries to open the v4l devicenode,
it first checks if there's still something active at the DVB side.

http://mcentral.de/hg/~mrec/v4l-dvb-experimental/file/f9f3e6bdd6fc/linux/drivers/media/video/em28xx/em2880-dvb.c

Line 471 - 484 if this would go into the dvb core we'd have a callback
for locking the device nodes.

Markus



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