[PATCH] ata: implement MODE SELECT command

Paolo Bonzini
2012-07-04T11:14:12Z

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;
+ 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);
+
+ 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_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)
+{
+ struct scsi_cmnd *scmd = qc->scsicmd;
+ struct ata_taskfile *tf = &qc->tf;
+ const u8 *cdb = scmd->cmnd;
+ const u8 *p;
+ u8 pg, spg;
+ unsigned six_byte, pg_len;
+ int len;
+
+ VPRINTK("ENTER\n");
+
+ /*
+ * Get the command buffer.
+ */
+ if (!scsi_sg_count(scmd))
+ goto invalid_fld;
+
+ p = page_address(sg_page(scsi_sglist(scmd)));
+
+ six_byte = (cdb[0] == MODE_SELECT);
+ if (six_byte) {
+ if (scmd->cmd_len < 5)
+ goto invalid_fld;
+
+ len = cdb[4];
+ } else {
+ if (scmd->cmd_len < 9)
+ goto invalid_fld;
+
+ len = (cdb[7] << 8) | cdb[8];
+ }
+
+ /* Test early for possible overrun. */
+ if (scsi_sglist(scmd)->length < len)
+ goto invalid_fld;
+
+ p += six_byte ? 4 : 8;
+ len -= six_byte ? 4 : 8;
+
+ /* We only support PF=1, SP=0. */
+ if ((cdb[1] & 0x11) != 0x10)
+ goto invalid_fld;
+
+ if (len == 0)
+ goto skip;
+
+ /* Parse both possible formats for the mode page headers. */
+ pg = p[0] & 0x3f;
+ if (p[0] & 0x40) {
+ spg = p[1];
+ pg_len = (p[2] << 8) | p[3];
+ p += 4;
+ len -= 4;
+ } else {
+ spg = 0;
+ pg_len = p[1];
+ p += 2;
+ len -= 2;
+ }
+
+ /* We only support setting one page at a time. */
+ if (len != pg_len)
+ goto invalid_fld;
+
+ /*
+ * 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;
+
+ switch (pg) {
+ case CACHE_MPAGE:
+ if (ata_mselect_caching(tf, p, pg_len))
+ goto invalid_fld;
+ break;
+
+ default: /* invalid page code */
+ goto invalid_fld;
+ }
+ return 0;
+
+ invalid_fld:
+ ata_scsi_set_sense(scmd, ILLEGAL_REQUEST, 0x24, 0x0);
+ /* "Invalid field in cbd" */
+ 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
@@ -3120,6 +3257,11 @@ 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;
}
@@ -3312,11 +3454,6 @@ 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