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Subject[PATCH v3 2/2] ata: implement MODE SELECT command
Date
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. The set of changeable parameters
answered by MODE SENSE is also adjusted accordingly.

Cc: Sergei Shtylyov <sshtylyov@mvista.com>
Cc: Jeff Garzik <jgarzik@pobox.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
v2->v3: ensure that only the first page of the sg list is
accessed

drivers/ata/libata-scsi.c | 194 +++++++++++++++++++++++++++++++++++++++++++--
1 files changed, 188 insertions(+), 6 deletions(-)

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index d5aeb26..e13cf0c 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -2244,7 +2244,7 @@ static void modecpy(u8 *dest, const u8 *src, int n, bool changeable)
static unsigned int ata_msense_caching(u16 *id, u8 *buf, bool changeable)
{
modecpy(buf, def_cache_mpage, sizeof(def_cache_mpage), changeable);
- if (!changeable && ata_id_wcache_enabled(id))
+ if (changeable || ata_id_wcache_enabled(id))
buf[2] |= (1 << 2); /* write cache enable */
if (!changeable && !ata_id_rahead_enabled(id))
buf[12] |= (1 << 5); /* disable read ahead */
@@ -3108,6 +3108,188 @@ static unsigned int ata_scsi_write_same_xlat(struct ata_queued_cmd *qc)
}

/**
+ * ata_mselect_caching - Simulate MODE SELECT for caching info page
+ * @qc: Storage for translated ATA taskfile
+ * @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 int ata_mselect_caching(struct ata_queued_cmd *qc,
+ const u8 *buf, int len)
+{
+ struct ata_taskfile *tf = &qc->tf;
+ struct ata_device *dev = qc->dev;
+ char mpage[CACHE_MPAGE_LEN];
+ u8 wce;
+
+ /*
+ * The first two bytes of def_cache_mpage are a header, so offsets
+ * in mpage are off by 2 compared to buf. Same for len.
+ */
+
+ if (len != CACHE_MPAGE_LEN - 2)
+ return -EINVAL;
+
+ wce = buf[0] & (1 << 2);
+
+ /*
+ * Check that read-only bits are not modified.
+ */
+ ata_msense_caching(dev->id, mpage, false);
+ mpage[2] &= ~(1 << 2);
+ mpage[2] |= wce;
+ if (memcmp(mpage + 2, buf, CACHE_MPAGE_LEN - 2) != 0)
+ return -EINVAL;
+
+ tf->flags |= ATA_TFLAG_DEVICE | ATA_TFLAG_ISADDR;
+ tf->protocol = ATA_PROT_NODATA;
+ tf->nsect = 0;
+ tf->command = ATA_CMD_SET_FEATURES;
+ tf->feature = wce ? SETFEATURES_WC_ON : SETFEATURES_WC_OFF;
+ return 0;
+}
+
+/**
+ * ata_scsiop_mode_select - Simulate 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)
+{
+ struct scsi_cmnd *scmd = qc->scsicmd;
+ const u8 *cdb = scmd->cmnd;
+ const u8 *p;
+ u8 pg, spg;
+ unsigned six_byte, pg_len, hdr_len, bd_len;
+ int len;
+
+ VPRINTK("ENTER\n");
+
+ six_byte = (cdb[0] == MODE_SELECT);
+ if (six_byte) {
+ if (scmd->cmd_len < 5)
+ goto invalid_fld;
+
+ len = cdb[4];
+ hdr_len = 4;
+ } else {
+ if (scmd->cmd_len < 9)
+ goto invalid_fld;
+
+ len = (cdb[7] << 8) + cdb[8];
+ hdr_len = 8;
+ }
+
+ /* We only support PF=1, SP=0. */
+ if ((cdb[1] & 0x11) != 0x10)
+ goto invalid_fld;
+
+ /* Test early for possible overrun. */
+ if (!scsi_sg_count(scmd) || scsi_sglist(scmd)->length < len)
+ goto invalid_param_len;
+
+ p = page_address(sg_page(scsi_sglist(scmd)));
+
+ /* Move past header and block descriptors. */
+ if (len < hdr_len)
+ goto invalid_param_len;
+
+ if (six_byte)
+ bd_len = p[3];
+ else
+ bd_len = (p[6] << 8) + p[7];
+
+ len -= hdr_len;
+ p += hdr_len;
+ if (len < bd_len)
+ goto invalid_param_len;
+ if (bd_len != 0 && bd_len != 8)
+ goto invalid_param;
+
+ len -= bd_len;
+ p += bd_len;
+ if (len == 0)
+ goto skip;
+
+ /* Parse both possible formats for the mode page headers. */
+ pg = p[0] & 0x3f;
+ if (p[0] & 0x40) {
+ if (len < 4)
+ goto invalid_param_len;
+
+ spg = p[1];
+ pg_len = (p[2] << 8) | p[3];
+ p += 4;
+ len -= 4;
+ } else {
+ if (len < 2)
+ goto invalid_param_len;
+
+ spg = 0;
+ pg_len = p[1];
+ p += 2;
+ len -= 2;
+ }
+
+ /*
+ * No mode subpages supported (yet) but asking for _all_
+ * subpages may be valid
+ */
+ if (spg && (spg != ALL_SUB_MPAGES))
+ goto invalid_param;
+ if (pg_len > len)
+ goto invalid_param_len;
+
+ switch (pg) {
+ case CACHE_MPAGE:
+ if (ata_mselect_caching(qc, p, pg_len) < 0)
+ goto invalid_param;
+ break;
+
+ default: /* invalid page code */
+ goto invalid_param;
+ }
+
+ /*
+ * Only one page has changeable data, so we only support setting one
+ * page at a time.
+ */
+ if (len > pg_len)
+ goto invalid_param;
+
+ return 0;
+
+ invalid_fld:
+ /* "Invalid field in CDB" */
+ ata_scsi_set_sense(scmd, ILLEGAL_REQUEST, 0x24, 0x0);
+ return 1;
+
+ invalid_param:
+ /* "Invalid field in parameter list" */
+ ata_scsi_set_sense(scmd, ILLEGAL_REQUEST, 0x26, 0x0);
+ return 1;
+
+ invalid_param_len:
+ /* "Parameter list length error" */
+ ata_scsi_set_sense(scmd, ILLEGAL_REQUEST, 0x1a, 0x0);
+ return 1;
+
+ skip:
+ scmd->result = SAM_STAT_GOOD;
+ return 1;
+}
+
+/**
* ata_get_xlat_func - check if SCSI to ATA translation is possible
* @dev: ATA device
* @cmd: SCSI command opcode to consider
@@ -3147,6 +3329,11 @@ static inline ata_xlat_func_t ata_get_xlat_func(struct ata_device *dev, u8 cmd)
case ATA_16:
return ata_scsi_pass_thru;

+ case MODE_SELECT:
+ case MODE_SELECT_10:
+ return ata_scsi_mode_select_xlat;
+ break;
+
case START_STOP:
return ata_scsi_start_stop_xlat;
}
@@ -3339,11 +3526,6 @@ void ata_scsi_simulate(struct ata_device *dev, struct scsi_cmnd *cmd)
ata_scsi_rbuf_fill(&args, ata_scsiop_mode_sense);
break;

- case MODE_SELECT: /* unconditionally return */
- case MODE_SELECT_10: /* bad-field-in-cdb */
- ata_scsi_invalid_field(cmd);
- break;
-
case READ_CAPACITY:
ata_scsi_rbuf_fill(&args, ata_scsiop_read_cap);
break;
--
1.7.1


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