scsi: core: Detect support for command duration limits

[linux-2.6-block.git] / drivers / scsi / scsi.c

diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 62d9472e08e9850e02ae8c65af8cb3430fc4f684..c03814ce23ca0473cc21fd7dd766ac3dd0f59586 100644 (file)
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -570,6 +570,87 @@ int scsi_report_opcode(struct scsi_device *sdev, unsigned char *buffer,
 }
 EXPORT_SYMBOL(scsi_report_opcode);
 
+#define SCSI_CDL_CHECK_BUF_LEN 64
+
+static bool scsi_cdl_check_cmd(struct scsi_device *sdev, u8 opcode, u16 sa,
+                              unsigned char *buf)
+{
+       int ret;
+       u8 cdlp;
+
+       /* Check operation code */
+       ret = scsi_report_opcode(sdev, buf, SCSI_CDL_CHECK_BUF_LEN, opcode, sa);
+       if (ret <= 0)
+               return false;
+
+       if ((buf[1] & 0x03) != 0x03)
+               return false;
+
+       /* See SPC-6, one command format of REPORT SUPPORTED OPERATION CODES */
+       cdlp = (buf[1] & 0x18) >> 3;
+       if (buf[0] & 0x01) {
+               /* rwcdlp == 1 */
+               switch (cdlp) {
+               case 0x01:
+                       /* T2A page */
+                       return true;
+               case 0x02:
+                       /* T2B page */
+                       return true;
+               }
+       } else {
+               /* rwcdlp == 0 */
+               switch (cdlp) {
+               case 0x01:
+                       /* A page */
+                       return true;
+               case 0x02:
+                       /* B page */
+                       return true;
+               }
+       }
+
+       return false;
+}
+
+/**
+ * scsi_cdl_check - Check if a SCSI device supports Command Duration Limits
+ * @sdev: The device to check
+ */
+void scsi_cdl_check(struct scsi_device *sdev)
+{
+       bool cdl_supported;
+       unsigned char *buf;
+
+       buf = kmalloc(SCSI_CDL_CHECK_BUF_LEN, GFP_KERNEL);
+       if (!buf) {
+               sdev->cdl_supported = 0;
+               return;
+       }
+
+       /* Check support for READ_16, WRITE_16, READ_32 and WRITE_32 commands */
+       cdl_supported =
+               scsi_cdl_check_cmd(sdev, READ_16, 0, buf) ||
+               scsi_cdl_check_cmd(sdev, WRITE_16, 0, buf) ||
+               scsi_cdl_check_cmd(sdev, VARIABLE_LENGTH_CMD, READ_32, buf) ||
+               scsi_cdl_check_cmd(sdev, VARIABLE_LENGTH_CMD, WRITE_32, buf);
+       if (cdl_supported) {
+               /*
+                * We have CDL support: force the use of READ16/WRITE16.
+                * READ32 and WRITE32 will be used for devices that support
+                * the T10_PI_TYPE2_PROTECTION protection type.
+                */
+               sdev->use_16_for_rw = 1;
+               sdev->use_10_for_rw = 0;
+
+               sdev->cdl_supported = 1;
+       } else {
+               sdev->cdl_supported = 0;
+       }
+
+       kfree(buf);
+}
+
 /**
  * scsi_device_get  -  get an additional reference to a scsi_device
  * @sdev:      device to get a reference to