[SCSI] Add a report opcode helper

The REPORT SUPPORTED OPERATION CODES command can be used to query
whether a given opcode is supported by a device. Add a helper function
that allows us to look up commands.

We only issue RSOC if the device reports compliance with SPC-3 or
later. But to err on the side of caution we disable the command for ATA,
FireWire and USB.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

1 files changed, 45 insertions, 0 deletions

diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 2936b447cae9..2c0d0ec8150b 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -55,6 +55,7 @@
 #include <linux/cpu.h>
 #include <linux/mutex.h>
 #include <linux/async.h>
+#include <asm/unaligned.h>
 
 #include <scsi/scsi.h>
 #include <scsi/scsi_cmnd.h>
@@ -1062,6 +1063,50 @@ int scsi_get_vpd_page(struct scsi_device *sdev, u8 page, unsigned char *buf,
 EXPORT_SYMBOL_GPL(scsi_get_vpd_page);
 
 /**
+ * scsi_report_opcode - Find out if a given command opcode is supported
+ * @sdev:       scsi device to query
+ * @buffer:     scratch buffer (must be at least 20 bytes long)
+ * @len:        length of buffer
+ * @opcode:     opcode for command to look up
+ *
+ * Uses the REPORT SUPPORTED OPERATION CODES to look up the given
+ * opcode. Returns 0 if RSOC fails or if the command opcode is
+ * unsupported. Returns 1 if the device claims to support the command.
+ */
+int scsi_report_opcode(struct scsi_device *sdev, unsigned char *buffer,
+                       unsigned int len, unsigned char opcode)
+{
+        unsigned char cmd[16];
+        struct scsi_sense_hdr sshdr;
+        int result;
+
+        if (sdev->no_report_opcodes || sdev->scsi_level < SCSI_SPC_3)
+                return 0;
+
+        memset(cmd, 0, 16);
+        cmd[0] = MAINTENANCE_IN;
+        cmd[1] = MI_REPORT_SUPPORTED_OPERATION_CODES;
+        cmd[2] = 1;             /* One command format */
+        cmd[3] = opcode;
+        put_unaligned_be32(len, &cmd[6]);
+        memset(buffer, 0, len);
+
+        result = scsi_execute_req(sdev, cmd, DMA_FROM_DEVICE, buffer, len,
+                                  &sshdr, 30 * HZ, 3, NULL);
+
+        if (result && scsi_sense_valid(&sshdr) &&
+            sshdr.sense_key == ILLEGAL_REQUEST &&
+            (sshdr.asc == 0x20 || sshdr.asc == 0x24) && sshdr.ascq == 0x00)
+                return 0;
+
+        if ((buffer[1] & 3) == 3) /* Command supported */
+                return 1;
+
+        return 0;
+}
+EXPORT_SYMBOL(scsi_report_opcode);
+
+/**
  * scsi_device_get  -  get an additional reference to a scsi_device
  * @sdev:       device to get a reference to
  *