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

[Arnd Bergmann]

On Wednesday 29 November 2006 13:41, Geert Uytterhoeven wrote:
> Are there any disadvantages of using a block driver instead?
> E.g. the internal disk interface is SATA, which supports hotplug (in theory, I
> don't know whether the actual SATA hardware and the HV support hotplugging the
> disk).

My guess is that inside of the kernel using a separate block driver
has only advantages. The value in the scsi layer lies mostly in the
common error handling for all scsi devices, which does not apply here.

From the user perspective, there is a significant difference between
using a block driver and a scsi driver, mostly because the device special
files are named differently. All scsi drives are named sd[a-z] or sr[0-9],
while a new driver would use a different name space, possibly a common
one for hard disc and compat disk type media, like we have on IDE.

Whether you consider this difference a disadvantage or not depends on your
personal opinion.

> The PS3 storage driver is used for HD, CD/DVD/BD, and 4 MiB of internal flash.

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.
 
> Memory Stick, CompactFlash and SD/MMC media are on the USB bus.

Ok, so that is at least nonproblematic, although it means that CF and
SD/MMC access is less efficient than it could be, because USB mass storage
devices don't allow to issue erase commands, unlike the native interfaces.

	Arnd <><