Re: Order of dvb devices

[Andreas Besse <besse@motama.com>]

Manu Abraham wrote:
> On Sat, Jan 16, 2010 at 3:00 AM, Oliver Endriss <o.endriss@gmx.de> wrote:
>   
>> 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.
>>     
>
>
> True, the ordering is not exactly the same everytime. One will need to
> provide PCI Bus related info also to a practical udev configuration to
> get things sorted out in a sane way, rather than anything else.
>   
with "PCI Bus related info" you mean the KERNELS parameter which is
reported by udevinfo?

udevinfo -a -p $(udevinfo -q path -n /dev/dvb/adapter0/frontend0)
[...]
  looking at parent device '/devices/pci0000:00/0000:00:1e.0/0000:08:00.0':
    KERNELS=="0000:08:00.0"
    SUBSYSTEMS=="pci"

does this KERNELS parameter always match the Slot-Id of "lspci -vmm" ?
Slot:   08:00.0
Class:  Multimedia controller
Vendor: Philips Semiconductors
Device: SAA7146
SVendor:        Technotrend Systemtechnik GmbH
SDevice:        S2-3200
Rev:    01

is it right that the Slot-Id is deterministic for PCI/PCIe based systems?