Re: Re: BUG in kernel: Wrong Handling of USB HDD’s in scsiglue(slave_configure) and scsi/sd(sd_read_cache_type)
From: Alan Stern
Date: Mon Oct 03 2011 - 14:11:00 EST
On Mon, 3 Oct 2011, Douglas Gilbert wrote:
> The RBC device parameters mode page followed by a Power
> Condition mode page. The RBC device parameters mode page
> is the only SCSI page I have seen (mode, log, VPD, etc)
> with a 5 byte field!
> Decoded response to a probable MODE SENSE(6) "fetch all
> pages" command:
> RBC device parameters mpage:
> WCD=0 [double negative: write cache enabled]
> Logical block size: 512 bytes
> Number of logical blocks: 0x12A19EB0 *** [160 GB]
> Power/performance: 0x3c
> READD: 0 [READ enabled]
> WRITED: 0 [WRITE enabled]
> FORMATD: 0 [FORMAT UNIT enabled]
> LOCKD: 1 [media cannot be locked]
> Power Condition mpage:
> STANDBY_CONDITION_TIMER=0xbb8 [300 seconds]
> References: rbc-r10a.pdf  + spc3r26 
> Hopefully Seagate will switch to UAS(P) in the near future.
> *** That is _not_ the address of the last valid LB as in
> the SCSI READ CAPACITY command!
Thanks for the explanation.
> > Would it make sense to assume write caching is present and enabled if
> > the drive does not provide a Caching page?
> No. You need to also take into account the RBC
> device parameters mode page if present. See above.
All right, suppose neither page is present. Does it then make sense to
assume by default that write caching is enabled?
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