Messages in this thread | | | Date | Thu, 15 Nov 2007 15:59:25 -0500 | From | Mark Lord <> | Subject | Re: libata/PATA: GPCMD_SET_STREAMING via SG_IO does nothing |
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Bartlomiej Zolnierkiewicz wrote: > Hi, > > On Wednesday 14 November 2007, Mark Lord wrote: >> Sebastian Kemper wrote: >>> Hi Mark! >>> >>> On Wed, Nov 14, 2007 at 11:41:37AM -0500, Mark Lord wrote: >>>> Ahh.. got it. The host_status returned (not checked by that code) was 7, >>>> which means "host error". >>>> >>>> In this case, that's because the cmd_len is (16), which is too large for >>>> ATAPI. >>>> It needs to be changed to (12) instead. >>> I don't understand. You seem to use a cmd_len of 16 in hdparm yourself. >> .. >> >> Really? Where? >> >> >>> And why does it work with the "old" ATA driver and not with libata if >>> 16 is too large for ATAPI in general? >> .. >> >> Now that *is* the question. >> And the answer appears to be that ide-cd.c ignores the passed-in cmd_len, >> and replaces it with: >> >> cmd_len = COMMAND_SIZE(rq->cmd[0]); >> >> That's a SCSI macro to calculate the correct cmd_len based on the SCSI opcode, >> which is very appropriate here. We should do that too (we don't) in libata. >> >> But not exactly as IDE does it -- that's actually a bug: the code needs to also >> check that the new cmd_len is no larger than the original, or we'll get an Oops. >> >> I'll cook up a patch for that shortly and try it before posting it here. > > Could you please also fix ide-cd while at it? ..
ide-cd already does the COMMAND_SIZE() thingie, so that fix is not needed.
The only bug there is that it doesn't check for the possibility of a 16-byte opcode being issued with only a 12-byte CDB underneath. In practice, this doesn't seem to hurt anything.
I'm no longer familiar enough with the code there to reliably fix it.
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