Re: Order of dvb devices

[Oliver Endriss <o.endriss@gmx.de>]

Devin Heitmueller wrote:
> On Thu, Jan 14, 2010 at 11:01 AM, Andreas Besse <besse@motama.com> wrote:
> > yes if there are different drivers I already observed the behaviour that
> > the ordering gets flipped after reboot.
> >
> > But if I assume, that there is only *one* driver that is loaded (e.g.
> > budget_av) for all dvb cards in the system, how is the ordering of these
> > devices determined? How does the driver "search" for available dvb cards?

The driver does not 'search' for a card. The driver registers the ids of
all supported cards with the pci subsystem of the kernel.

When the pci subsystem detects a new card, it calls the 'probe' routine
of the driver (for example saa7146_init_one for saa7146-based cards).
So the ordering is determined by the pci subsystem.

> I believe your assumption is incorrect.  I believe the enumeration
> order is not deterministic even for multiple instances of the same
> driver.  It is not uncommon to hear mythtv users complain that "I have
> two PVR-150 cards installed in my PC and the order sometimes get
> reversed on reboot".

Afaik the indeterministic behaviour is caused by udev, not by the
kernel. We never had these problems before udev was introduced.

CU
Oliver

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