[linux-dvb] [RFC PATCH] Choose dvb adapter number with a driver specific module option

Manu Abraham abraham.manu at gmail.com
Sat Aug 4 06:30:11 CEST 2007


On 8/4/07, Michael Krufky <mkrufky at linuxtv.org> wrote:
> Manu Abraham wrote:
> > On 8/4/07, Janne Grunau <janne-dvb at grunau.be> wrote:
> >> On Saturday 04 August 2007 00:02:29 Manu Abraham wrote:
> >>> Do we really want to have adapter numbers in DVB bridge drivers ?
> >>> IMHO, it doesn't look pleasing to have that.
> >> I think it's worthwhile to have it.
> >>> Is there any other possible better alternatives ?
> >> Something similiar is possible with udev rules but I wouldn't say that
> >> it is a better alternative.
> >
> > Why ? If you can achieve the same without any code change, doesn't
> > that look better ?
>
> using a module option to specify adapter number is a _much_ more user friendly solution, as opposed to udev rules.
>


Yuck. I just wonder why other char drivers in the Linux kernel do not
have such a necessity, you have the same problem there as well.


> >>> If it is that
> >>> absolute a necessity, can we hide the ugliness in dvb-core at least ?
> >> I'm not really sure what you mean exactly. If you want to avoid changes
> >> in the bridge drivers I don't see a way to archieve that. If you want
> >> the changes as small as possible look at the final patch.
> >
> > That one looks better than your first patch. (Although i hate having a
> > MAX limit defined)
>
> The MAX limit was already there beforehand -- Janne only moved the setting of it from dvbdev.c to dvbdev.h.
>


That cruft/limit comes from the old allocation. The v2.4 kernel
supported only 255 major devices with 255 minor numbers. Larger
devices have been a feature that 2.6 brought forward.

Though we have had this number incremented a while later on, we still
have some cruft in there. That limitation comes in the form of that
limitation, though if someone wants to have more devices having to
tweak MAX_DEVICES, :-/

Having limitations that way is not quite nice. That brings up the old
devfs vs udev memories
http://kernel.org/pub/linux/utils/kernel/hotplug/udev_vs_devfs



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