Re: Removal of pci_find_* in 2.5

[Jeff Garzik <jgarzik@mandrakesoft.com>]

Alan Cox wrote:
> On Sat, 2002-07-13 at 05:41, Jeff Garzik wrote:
> 
>>ordering, is simply hard-coding something that should really be in 
>>userspace.  Depending on pci_find_device logic / link order to 
>>still-boot-the-system after adding new hardware sounds like an 
>>incredibly fragile hope, not a reliable system users can trust.
> 
> 
> For hot plugging obvious. At system boot time however the ordering and
> seeing the ordering is rather important because in many cases the
> ordering is what tells you about things like IDE controller pairing. It
> tells you what order to assign many scsi devices because the ordering is
> defined by their BIOS ROM.
> 
> One way to handle this generically would be to use pci_register_device,
> but in the register function for such wacky devices during boot up we
> merely keep track of what we have to look into. 


My point is that depending on any method of internal kernel ordering is 
fragile.

I would rather have the kernel export which drives are listed in CMOS / 
BIOS ROM, and let userspace say "my boot drive is the nth BIOS-listed 
drive."  For example, looking through the aic7xxx (or was it 
ncr53c8xxx?) drive, it gets boot drive ordering from BIOS/CMOS.  That 
piece of info can either be exported by driverfs from the low-level SCSI 
driver, or by a separate, tiny ncr53c8xxx_boot_drive driver.

Depending on pci_find_* ordering is very situation-dependent, and only 
covers N cases.  Then you have another N cases covered by the order in 
which you modprobe key drivers.  Then you have another N cases covered 
by special case code somewhere.  You'll never get all these cases right, 
in the kernel, the way the user wants.  That's why I say the 
responsibility for figuring out the boot drive should be pushed to 
initrd/initramfs.

	Jeff