scsi: core: Detect support for command duration limits

Introduce the function scsi_cdl_check() to detect if a device supports
command duration limits (CDL). Support for the READ 16, WRITE 16, READ 32
and WRITE 32 commands are checked using the function scsi_report_opcode()
to probe the rwcdlp and cdlp bits as they indicate the mode page defining
the command duration limits descriptors that apply to the command being
tested.

If any of these commands support CDL, the field cdl_supported of struct
scsi_device is set to 1 to indicate that the device supports CDL.

Support for CDL for a device is advertizes through sysfs using the new
cdl_supported device attribute. This attribute value is 1 for a device
supporting CDL and 0 otherwise.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Co-developed-by: Niklas Cassel <niklas.cassel@wdc.com>
Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
Link: https://lore.kernel.org/r/20230511011356.227789-9-nks@flawful.org
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/Documentation/ABI/testing/sysfs-block-device b/Documentation/ABI/testing/sysfs-block-device
index 7ac7b19b2f7224572652bf850e51f575757fd0ee..ffc3358cba570dc889c74eac6ffe2f5c6dd6dff2 100644 (file)
--- a/Documentation/ABI/testing/sysfs-block-device
+++ b/Documentation/ABI/testing/sysfs-block-device
@@ -95,3 +95,12 @@ Description:
                This file does not exist if the HBA driver does not implement
                support for the SATA NCQ priority feature, regardless of the
                device support for this feature.
+
+
+What:          /sys/block/*/device/cdl_supported
+Date:          May, 2023
+KernelVersion: v6.5
+Contact:       linux-scsi@vger.kernel.org
+Description:
+               (RO) Indicates if the device supports the command duration
+               limits feature found in some ATA and SCSI devices.

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

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index d217be323cc690f0736df29349d085bd27575170..aa13feb17c62605a15379cae725514acf2a8a09c 100644 (file)
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -1087,6 +1087,8 @@ static int scsi_add_lun(struct scsi_device *sdev, unsigned char *inq_result,
        if (sdev->scsi_level >= SCSI_3)
                scsi_attach_vpd(sdev);
 
+       scsi_cdl_check(sdev);
+
        sdev->max_queue_depth = sdev->queue_depth;
        WARN_ON_ONCE(sdev->max_queue_depth > sdev->budget_map.depth);
        sdev->sdev_bflags = *bflags;
@@ -1624,6 +1626,7 @@ void scsi_rescan_device(struct device *dev)
        device_lock(dev);
 
        scsi_attach_vpd(sdev);
+       scsi_cdl_check(sdev);
 
        if (sdev->handler && sdev->handler->rescan)
                sdev->handler->rescan(sdev);

diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 603e8fcfcb8a0c0a80beeceedd5e3391abd25133..98fcbbf1c1e36b62a17517832ab1e850d975a881 100644 (file)
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -670,6 +670,7 @@ sdev_rd_attr (scsi_level, "%d\n");
 sdev_rd_attr (vendor, "%.8s\n");
 sdev_rd_attr (model, "%.16s\n");
 sdev_rd_attr (rev, "%.4s\n");
+sdev_rd_attr (cdl_supported, "%d\n");
 
 static ssize_t
 sdev_show_device_busy(struct device *dev, struct device_attribute *attr,
@@ -1300,6 +1301,7 @@ static struct attribute *scsi_sdev_attrs[] = {
        &dev_attr_preferred_path.attr,
 #endif
        &dev_attr_queue_ramp_up_period.attr,
+       &dev_attr_cdl_supported.attr,
        REF_EVT(media_change),
        REF_EVT(inquiry_change_reported),
        REF_EVT(capacity_change_reported),

diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index c93c5aaf637ee42daf8303cffbcaf063b7b1ba35..6b8df9e253a0f45633959363345c894783022a6d 100644 (file)
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -218,6 +218,8 @@ struct scsi_device {
        unsigned silence_suspend:1;     /* Do not print runtime PM related messages */
        unsigned no_vpd_size:1;         /* No VPD size reported in header */
 
+       unsigned cdl_supported:1;       /* Command duration limits supported */
+
        unsigned int queue_stopped;     /* request queue is quiesced */
        bool offline_already;           /* Device offline message logged */
 
@@ -364,6 +366,7 @@ extern int scsi_register_device_handler(struct scsi_device_handler *scsi_dh);
 extern void scsi_remove_device(struct scsi_device *);
 extern int scsi_unregister_device_handler(struct scsi_device_handler *scsi_dh);
 void scsi_attach_vpd(struct scsi_device *sdev);
+void scsi_cdl_check(struct scsi_device *sdev);
 
 extern struct scsi_device *scsi_device_from_queue(struct request_queue *q);
 extern int __must_check scsi_device_get(struct scsi_device *);