[libata] scsi: implement MODE SELECT command

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.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index 67d23bd..e3bda07 100644 (file)
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -2243,7 +2243,7 @@ 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 */
@@ -3107,6 +3107,188 @@ 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
@@ -3146,6 +3328,11 @@ 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;
        }
@@ -3338,11 +3525,6 @@ 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;