[mythtv-users] Cards keep changing /dev/videoX devices...

Nick Morrott knowledgejunkie at gmail.com
Mon Jun 18 00:17:39 UTC 2007


On 17/06/07, R. G. Newbury <newbury at mandamus.org> wrote:
> Alan Calvert wrote:
> > Nick Morrott wrote:
> >> On 15/06/07, R. G. Newbury <newbury at mandamus.org> wrote:
> >>> Alan Calvert wrote:
> >>>> Yep, blacklisting everything and ordering the module loads explicitly in
> >>>> rc.local works, as does using a sledgehammer to crack a nut. Simply allocating
> >>>> video device numbers explicitly by means of module options also works.
> >>>>
> >>>> No desire for argument here, but some of the advice presented was simply false
> >>>> and misleading.
> >>> Nothing false. I'll put my hand up for being misleading about the module
> >>> being 'built into' the kernel.
> >>>
> >>> There are NO module options for the cx8800 which allow you to force it
> >>> to a specific video device, as there is for the ivtv driver. The only
> >>> control method is load order. So you have to know what is being loaded
> >> What does the video_nr parameter for the cx8800 module do? modinfo cx8800 says
> >>
> >> video_nr:video device numbers (array of int)
> >
> > The module parameter to control cx8800 video device number allocation certainly does
> > exist, at least on current kernels. From the driver source, cx88-video.c
> >   MODULE_PARM_DESC(video_nr,"video device numbers");
> >   MODULE_PARM_DESC(vbi_nr,"vbi device numbers");
> >   MODULE_PARM_DESC(radio_nr,"radio device numbers");
> > and 'modinfo cx8800' on my box returns
> >   parm:           video_nr:video device numbers (array of int)
> >
> > It explicitly sets the video device number(s) to be used by this module. Eg, with
> > just one card
> >   options cx8800 video_nr=7 radio_nr=7 vbi_nr=7
> > would result in /dev/video7, /dev/radio7, /dev/vbi7
> >
> > With more than one card, the mysterious "array of int" comes in, eg, for three cards
> >   options cx8800 video_nr=3,4,5 would result in explicit allocation of
> > /dev/video3, /dev/video4, /dev/video5 (every time!).
>
> This is a recent addition to the driver then. Definitely NOT in FC5
> which is what the mythbox is running (not borken, did not frix it!) It
> is in fc6 on this laptop.

It's on my FC4 backend running a 2.6.16 kernel, which I where I got
the earlier information:

[mythtv at homer ~]$ /sbin/modinfo cx8800
filename:
/lib/modules/2.6.16-1.2111_FC4/kernel/drivers/media/video/cx88/cx8800.ko
license:        GPL
author:         Gerd Knorr <kraxel at bytesex.org> [SuSE Labs]
description:    v4l2 driver module for cx2388x based TV cards
srcversion:     F930BE26E8BE9EC89738DEE
alias:          pci:v000014F1d00008800sv*sd*bc*sc*i*
depends:
video-buf,cx88xx,videodev,btcx-risc,v4l2-common,v4l1-compat,compat_ioctl32
vermagic:       2.6.16-1.2111_FC4 686 REGPARM 4KSTACKS gcc-4.0
parm:           vbibufs:number of vbi buffers, range 2-32 (int)
parm:           vbi_debug:enable debug messages [vbi] (int)
parm:           video_nr:video device numbers (array of int)
parm:           vbi_nr:vbi device numbers (array of int)
parm:           radio_nr:radio device numbers (array of int)
parm:           video_debug:enable debug messages [video] (int)
parm:           irq_debug:enable debug messages [IRQ handler] (int)
parm:           vid_limit:capture memory limit in megabytes (int)


It's also in the V4L source from Tue Aug 16 17:23:46 2005 +0000 (22
months ago)- the earliest available revision in the V4L repo
(http://linuxtv.org/hg/v4l-dvb/file/e3f0d0cc3a16/linux/drivers/media/video/cx88/cx88-video.c).

I'm not sure what happened in FC5 (which shipped with a 2.6.15
kernel). I skipped it and later installed FC6 on a couple of boxes
(I've always skipped the odd numbered releases). I'll update them over
the summer to CentOS 5, as FC4 is a bit long in the tooth now.

-- 
Nick

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