[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>

1 files changed, 188 insertions, 6 deletions

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index 67d23bd87950..e3bda074fa12 100644
--- 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;