Open Firmware: search devalias children for disks

[Hollis Blanchard]

The current Open Firmware code only examines the devaliases when 
searching for disks present. (In general we probably want to search the 
whole device tree, but this behavior is ok for now.)

However when SCSI disks are present, the devalias is to the SCSI 
controller node, and under that are the block- and byte-oriented 
devices sd and st. Example:
        /bandit/gc/53c94
                /address@hidden,0
                /address@hidden,0

This patch (for comment only right now) allows grub2 to consider the 
children of devaliases when looking for disks, which lets it find the 
sd node above.

grub_ofdisk_open() was modified to avoid resolving aliases by hand; 
OF's open and finddevice do it for us. Also the error checking it was 
doing was a little off.

However, note that I had to comment out the ":0" being appended to the 
device path (e.g. "scsi/sd:0"). I'm still not sure why, but when the 
":0" was present, open and close on the block device would succeed but 
seek failed. :( More investigation may be needed, as I *think* the 
stage1 loader loaded grubof using ":0" in the device name (as seen in 
/chosen/bootpath). But with this patch on top of all the other patches 
I've sent so far, I get the following output:

grub> ls
(scsi/sd) (scsi/sd,0) (scsi/sd,1) (scsi/sd,2) (scsi/sd,3) (scsi/sd,4) 
(scsi/sd,5)
grub> ls (scsi/sd,5)/
lost+found/ dev/ etc/ tmp/ var/ proc/ bin/ boot/ home/ lib/ mnt/ opt/ 
root/ sbin/ usr/ halt

That's pretty good. :)

-Hollis

grub-ofdisk-scsi.diff
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