Re: [PATCH 2.6.18-rc4 1/5] ieee1394: sbp2: workaround for write protect bit of Initio firmware

[Linus Torvalds <torvalds@osdl.org>]

On Sun, 27 Aug 2006, Stefan Richter wrote:
>
> Yet another mode pages related bug of Initio firmwares was seen.
> INIC-1530 with a firmware by Initio responded with garbage to MODE SENSE
> (10).  Some HDDs were therefore incorrectly marked as write protected:
> http://bugzilla.kernel.org/show_bug.cgi?id=6947

Why does sbp2scsi_slave_configure() set "use_10_for_ms" in the first 
place?

Almost all the other SCSI code seems to default to using the 6-byte 
version, and then only uses the 10-byte version if they have some specific 
reason to do so.

I don't think there really is _ever_ any reason to use the 10-byte version 
if the 6-byte version is expected to work. Is there?

Examples:

 - scsi_add_lun() only sets the 10-byte MS for things that are 
   black-listed to set it (BLIST_USE_10_BYTE_MS)

   In fact, I don't see _anything_ in the source code that actually does 
   set that, so as far as I can see, scsi_add_lun() _never_ asks to use 
   the 10-byte modesense.

 - libata does set the 10-byte modesense for all SATA devices (but 
   scsi_lib.c might clear it if we get a bad status back).

 - USB devices set the 10-byte version _only_ if it's a non-disk device, 
   or if the subclass of the device is not SCSI.

Anyway, it would appear that sbp2 is the odd man out in setting up for a 
10-byte modesense, and then having to have strange magic rules for 
clearing it again.

Is there _really_ any reason to use the 10-byte version at all in the 
first place?

		Linus
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