Messages in this thread | | | Date | Wed, 04 Jul 2012 21:20:49 +0400 | From | Sergei Shtylyov <> | Subject | Re: [PATCH] ata: implement MODE SELECT command |
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On 07/04/2012 08:03 PM, Paolo Bonzini wrote:
>>> The cache_type file in sysfs lets users configure the disk cache in >>> write-through or write-back modes. However, ata disks do not support >>> writing to the file because they do not implement the MODE SELECT >>> command.
>>> This patch adds a translation from MODE SELECT (for the caching page >>> only) to the ATA SET FEATURES command.
>>> Cc: Jeff Garzik <jgarzik@pobox.com> >>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> >>> --- >>> drivers/ata/libata-scsi.c | 147 +++++++++++++++++++++++++++++++++++++++++++-- >>> 1 files changed, 142 insertions(+), 5 deletions(-)
>>> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c >>> index 41cde45..e7702d3 100644 >>> --- a/drivers/ata/libata-scsi.c >>> +++ b/drivers/ata/libata-scsi.c >>> @@ -3081,6 +3081,144 @@ static unsigned int ata_scsi_write_same_xlat(struct ata_queued_cmd *qc) >>> } >>> >>> /** >>> + * ata_mselect_caching - Simulate MODE SELECT for caching info page >>> + * @tf: taskfile to be filled >>> + * @buf: input buffer >>> + * @len: number of valid bytes in the input buffer >>> + * >>> + * Prepare a taskfile to modify caching information for the device. >>> + * >>> + * LOCKING: >>> + * None. >>> + */ >>> +static unsigned int ata_mselect_caching(struct ata_taskfile *tf, const u8 *buf, >>> + int len) >>> +{ >>> + u8 wce;
>> Empty line after declaration block wouldn't hurt...
>>> + if (len == 0) >>> + return 1; >>> + >>> + /* >>> + * The first two bytes are a header, so offsets here are 2 less >>> + * than in ata_msense_caching. >>> + */ >>> + wce = buf[0] & (1 << 2);
>> Perhaps it's worth denying the command if the other page fields dfifer from >> 'def_cache_mpage' (i.e. all zeros)?
> I thought about it, but it seemed a useless complication.
If you bothered to implement that, go all the way. :-)
>>> +/** >>> + * ata_scsi_mode_select_xlat - Translate MODE SELECT 6, 10 commands >>> + * @qc: Storage for translated ATA taskfile >>> + * >>> + * Converts a MODE SELECT command to an ATA SET FEATURES taskfile. >>> + * Assume this is invoked for direct access devices (e.g. disks) only. >>> + * There should be no block descriptor for other device types. >>> + * >>> + * LOCKING: >>> + * spin_lock_irqsave(host lock) >>> + */ >>> +static unsigned int ata_scsi_mode_select_xlat(struct ata_queued_cmd *qc) >>> +{ [...] >>> + /* >>> + * No mode subpages supported (yet) but asking for _all_ >>> + * subpages may be valid >>> + */ >>> + if (spg && (spg != ALL_SUB_MPAGES)) >>> + goto invalid_fld; >>> + if (pg_len > len) >>> + goto invalid_fld;
>> It's valid to have buffer size less than data size.
> Perhaps for MODE SENSE, but not for MODE SELECT. Otherwise, where do > you get the mode data from?
They simply don't change?
> Anyhow, checking buffer size vs. data size is done early, in
> + /* Test early for possible overrun. */ > + if (scsi_sglist(scmd)->length < len) > + goto invalid_fld;
> not here. What this check is doing, is ensuring that the page data does > not extend past the end of the buffer.
That's what I say is valid. You can get incomplete data, according to the buffer size. Though maybe it was only my impression...
>>> + switch (pg) { >>> + case CACHE_MPAGE: >>> + if (ata_mselect_caching(tf, p, pg_len)) >>> + goto invalid_fld; >>> + break; >>> + >>> + default: /* invalid page code */ >>> + goto invalid_fld;
>> Page code is not a part of CDB, hence the sense code you'll return doesn't >> fit there.
> Yes, invalid field in parameter list probably would be better.
Or "parameter not supported" (0x26/0x01).
> Let me know if I should respin.
I'd prefer if you respin.
> Thanks for the review!
> Paolo
MBR, Sergei
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