HDIO_SCAN_HWIF causes hwif to "forget" PCI parent

[Andrey Borzenkov <arvidjaar@mail.ru>]

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I have notebook with ALi IDE interface:

00:04.0 IDE interface: ALi Corporation M5229 IDE (rev c3)

One of scripts called on Mandriva during suspend/resume calls hdparm -U for 
hdc on suspend and hdparm -R on resume.

Now, hdparm -U (HDIO_UNREGISTER_HWIF) completely wipes out hwif reinitializing 
it. It means, that also hwif->pci_dev is nulled. On hdparm -R 
(HDIO_SCAN_HWIF) it basically calls hwif_register without initializing 
pci_dev which means hdc appears in sysfs in different place:

before

lrwxrwxrwx  1 root root 0 Apr  7 23:53 /sys/block/hdc/device 
- -> ../../devices/pci0000:00/0000:00:04.0/ide1/1.0/

after

lrwxrwxrwx  1 root root 0 Apr  7 23:53 /sys/block/hdc/device 
- -> ../../devices/ide1/1.0/

this slightly confuses udev that receives a new path and regenerates cdrom 
links (OK this is no more kernel problem but how I noticed it in the first 
place :) so what has been cdrom0 before suddenly becomes cdrom1.

Looking at ide.c, I do not see any obvious ways to fix it. I appreciate any 
hint how this can be fixed; alternatively if libpata does not have this issue 
I am ready to test it.

Thank you

- -andrey
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