[Cbe-oss-dev] [FYI 24/27] ps3: storage driver

[Geoff Levand]

Arnd Bergmann wrote:
> On Wednesday 29 November 2006 19:58, Geoff Levand wrote:
>> 
>> > Ah, ok. There may be some value in representing the flash part as MTD
>> > instead of a raw block device then. That should at least handle writes
>> > more efficiently than your current read-modify-write cycle.
>> 
>> Do you mean just in terms of speed, or also static memory usage?  If it is
>> considerable re-work to set this up as MTD, I don't know if there will be
>> much advantage just for improving write speed since it will be a rare occasion
>> for the user to reprogram the bootloader.  What do you think?
> 
> It won't get around the 256kb vmalloc space for storing data on a
> read-modify-write cycle, but the algorithm used by drivers/mtd/mtdblock.c
> should be faster. If that is not relevant, then you can just as well
> leave the current code there.
> 
> Is there actually a file system present in the 4MB flash area, or just
> a kernel+ramdisk? If there is no fs at all, it may be a good idea to
> not do a block driver at all, but simply a misc character device
> that you can write the bootloader to and have it do the actual write
> when closing the device. This would be similar to what the IBM
> blades do for firmware update, but better ;-).

Yes, there is a filesystem of sorts, 512 byte segments with user preference
fields like the 'Other OS' boot flag and static IP addr where random access
is need to modify.  The layout is documented in the file
arch/powerpc/platforms/ps3/os-area.c, now in powerpc.git.

-Geoff