[PATCH v6 2/5] scsi: core: Add scsi_update_inquiry_data() for updating INQUIRY data

[Brian Bunker <brian@purestorage.com>]

Add a new function scsi_update_inquiry_data() that can safely update all
INQUIRY-derived fields for an existing SCSI device:

- Vendor, model, revision strings
- Peripheral qualifier and device type
- Capability flags (removable, lockable, tagged queuing support, etc.)
- ATA device detection and allow_restart setting

The function:
- Takes the inquiry_mutex to protect against concurrent sysfs reads
- Respects BLIST_ISROM and BLIST_NOTQ blacklist flags
- Returns 1 if device type or peripheral qualifier changed, indicating
  the caller should call device_reprobe() to re-match drivers
- Returns 0 on success with no changes requiring reprobe
- Returns negative errno on failure

This is the core infrastructure needed for updating INQUIRY data during
device rescan operations, which is required for proper ALUA unavailable
state handling.

Co-developed-by: Krishna Kant <krishna.kant@purestorage.com>
Signed-off-by: Krishna Kant <krishna.kant@purestorage.com>
Reviewed-by: Hannes Reinecke <hare@kernel.org>
Signed-off-by: Brian Bunker <brian@purestorage.com>
---
 drivers/scsi/scsi.c        | 178 +++++++++++++++++++++++++++++++++++++
 include/scsi/scsi_device.h |  13 +++
 2 files changed, 191 insertions(+)

diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 3af9e77847f7..b80378ecf485 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -61,6 +61,7 @@
 #include <scsi/scsi_cmnd.h>
 #include <scsi/scsi_dbg.h>
 #include <scsi/scsi_device.h>
+#include <scsi/scsi_devinfo.h>
 #include <scsi/scsi_driver.h>
 #include <scsi/scsi_eh.h>
 #include <scsi/scsi_host.h>
@@ -549,6 +550,183 @@ void scsi_attach_vpd(struct scsi_device *sdev)
 	kfree(vpd_buf);
 }
 
+/**
+ * scsi_update_inquiry_data - Update standard INQUIRY data for a SCSI device
+ * @sdev: The device to update
+ * @inq_result: Buffer containing new INQUIRY data
+ * @inq_len: Length of inquiry data
+ *
+ * Updates the standard INQUIRY data (vendor, model, rev, peripheral qualifier,
+ * device type, removable media flag) and capability flags derived from INQUIRY
+ * data for a SCSI device. This is used during both initial device setup and
+ * when reprobing a device to get fresh INQUIRY information. The old inquiry
+ * buffer is freed and replaced with the new data under the protection of
+ * inquiry_mutex.
+ *
+ * Blacklist flags (BLIST_ISROM, BLIST_NOTQ) are respected when updating
+ * device properties.
+ *
+ * Returns:
+ *   SCSI_INQ_UNCHANGED on success
+ *   SCSI_INQ_REPROBE_NEEDED if standard INQUIRY data changed (caller should reprobe)
+ *  -ENOMEM on allocation failure
+ *  -EINVAL if inquiry data is too short
+ */
+int scsi_update_inquiry_data(struct scsi_device *sdev,
+			     unsigned char *inq_result, size_t inq_len)
+{
+	unsigned char *new_inquiry;
+	unsigned char old_type;
+	unsigned char old_periph_qual;
+	bool had_prior_inquiry;
+
+	/*
+	 * Ensure we have at least the minimum standard INQUIRY data (36 bytes)
+	 * to safely access device type, vendor, model, rev, and capability flags.
+	 */
+	if (inq_len < 36) {
+		sdev_printk(KERN_WARNING, sdev,
+			    "INQUIRY data too short (%zu bytes), need at least 36\n",
+			    inq_len);
+		return -EINVAL;
+	}
+
+	/* Allocate new inquiry buffer */
+	new_inquiry = kmemdup(inq_result, inq_len, GFP_KERNEL);
+	if (!new_inquiry)
+		return -ENOMEM;
+
+	/* Update inquiry data under mutex protection */
+	mutex_lock(&sdev->inquiry_mutex);
+
+	/*
+	 * Save peripheral qualifier and device type before updating all
+	 * INQUIRY-derived fields. These are the only two values that
+	 * determine whether device_reprobe() is needed: type controls which
+	 * upper-layer driver (sd, st, sr, ...) is bound, and PQ controls
+	 * whether the LUN is accessible at all (scsi_bus_match() only matches
+	 * PQ == 0). Every other field — vendor, model, revision, capability
+	 * flags — is refreshed in place without any driver re-matching.
+	 */
+	had_prior_inquiry = (sdev->inquiry != NULL);
+	old_type = sdev->type;
+	old_periph_qual = sdev->inq_periph_qual;
+
+	kfree(sdev->inquiry);
+	sdev->inquiry = new_inquiry;
+	sdev->inquiry_len = inq_len;
+	strscpy(sdev->vendor, sdev->inquiry + INQUIRY_VENDOR_OFFSET);
+	strscpy(sdev->model, sdev->inquiry + INQUIRY_MODEL_OFFSET);
+	/*
+	 * memcpy() instead of strscpy() because strscpy() would read past
+	 * the end of sdev->inquiry if its length is exactly 36 bytes.
+	 */
+	memcpy(sdev->rev, sdev->inquiry + INQUIRY_REVISION_OFFSET,
+	       INQUIRY_REVISION_LEN);
+	sdev->rev[INQUIRY_REVISION_LEN] = '\0';
+	sdev->inq_periph_qual = (inq_result[0] >> 5) & 7;
+
+	/*
+	 * Compute scsi_level from INQUIRY bytes 2 and 3. This must be
+	 * updated under inquiry_mutex alongside the other INQUIRY-derived
+	 * fields so sysfs readers always see a consistent snapshot.
+	 */
+	sdev->scsi_level = inq_result[2] & 0x0f;
+	if (sdev->scsi_level >= 2 ||
+	    (sdev->scsi_level == 1 && (inq_result[3] & 0x0f) == 1))
+		sdev->scsi_level++;
+
+	/*
+	 * Check if this is an ATA device (SATA emulation layer).
+	 * ATA devices need allow_restart set to work around SATL power
+	 * management specifications.
+	 */
+	if (strncmp(sdev->vendor, "ATA     ", 8) == 0) {
+		sdev->is_ata = 1;
+		sdev->allow_restart = 1;
+	} else
+		sdev->is_ata = 0;
+
+	/*
+	 * Update device type from INQUIRY byte 0.
+	 * BLIST_ISROM is a quirk for devices that report wrong type but should
+	 * be treated as (removable) CD-ROM. Override to TYPE_ROM as exception.
+	 */
+	if (sdev->sdev_bflags & BLIST_ISROM) {
+		sdev->type = TYPE_ROM;
+		sdev->removable = 1;
+	} else {
+		sdev->type = inq_result[0] & 0x1f;
+		sdev->removable = (inq_result[1] & 0x80) >> 7;
+
+		/*
+		 * Some devices may respond with wrong type for well-known
+		 * logical units. Force well-known type to enumerate them
+		 * correctly.
+		 */
+		if (scsi_is_wlun(sdev->lun) && sdev->type != TYPE_WLUN) {
+			sdev_printk(KERN_WARNING, sdev,
+				"%s: correcting incorrect peripheral device type 0x%x for W-LUN 0x%16xhN\n",
+				__func__, sdev->type,
+				(unsigned int)sdev->lun);
+			sdev->type = TYPE_WLUN;
+		}
+	}
+
+	/*
+	 * Set lockable to match removable. Devices with removable media
+	 * can typically have their media locked/unlocked via the
+	 * ALLOW_MEDIUM_REMOVAL command.
+	 */
+	sdev->lockable = sdev->removable;
+
+	/* Update capability flags from INQUIRY byte 7 */
+	sdev->soft_reset = (inq_result[7] & 1) && ((inq_result[3] & 7) == 2);
+
+	/*
+	 * Update protocol support flags.
+	 * Only update ppr if we have enough INQUIRY data (>56 bytes) to check
+	 * byte 56, or if scsi_level indicates SCSI-3+ support. If we don't have
+	 * enough data, leave ppr unchanged to avoid incorrectly clearing it
+	 * during rescan with short INQUIRY.
+	 */
+	if (sdev->scsi_level >= SCSI_3 || inq_len > 56)
+		sdev->ppr = (sdev->scsi_level >= SCSI_3 ||
+			     (inq_len > 56 && inq_result[56] & 0x04)) ? 1 : 0;
+	sdev->wdtr = !!(inq_result[7] & 0x60);
+	sdev->sdtr = !!(inq_result[7] & 0x10);
+
+	/*
+	 * Update tagged queuing support from INQUIRY byte 7.
+	 * BLIST_NOTQ is an exception to force tagged queuing off.
+	 */
+	if (sdev->sdev_bflags & BLIST_NOTQ)
+		sdev->tagged_supported = 0;
+	else
+		sdev->tagged_supported = (sdev->scsi_level >= SCSI_2) &&
+					  (inq_result[7] & 2);
+	sdev->simple_tags = sdev->tagged_supported;
+
+	mutex_unlock(&sdev->inquiry_mutex);
+
+	if (had_prior_inquiry) {
+		if (old_type != sdev->type) {
+			sdev_printk(KERN_NOTICE, sdev,
+				    "device type changed from %d to %d\n",
+				    old_type, sdev->type);
+			return SCSI_INQ_REPROBE_NEEDED;
+		}
+		if (old_periph_qual != sdev->inq_periph_qual) {
+			sdev_printk(KERN_NOTICE, sdev,
+				    "peripheral qualifier changed from %d to %d\n",
+				    old_periph_qual, sdev->inq_periph_qual);
+			return SCSI_INQ_REPROBE_NEEDED;
+		}
+	}
+
+	return SCSI_INQ_UNCHANGED;
+}
+
 /**
  * scsi_report_opcode - Find out if a given command is supported
  * @sdev:	scsi device to query
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index e6fd6bc30644..743babf1602c 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -408,6 +408,19 @@ void scsi_attach_vpd(struct scsi_device *sdev);
 void scsi_cdl_check(struct scsi_device *sdev);
 int scsi_cdl_enable(struct scsi_device *sdev, bool enable);
 
+/**
+ * enum scsi_inq_update_result - Return values for scsi_update_inquiry_data()
+ * @SCSI_INQ_UNCHANGED: INQUIRY data updated, no reprobe needed
+ * @SCSI_INQ_REPROBE_NEEDED: INQUIRY data updated, standard INQUIRY data changed
+ */
+enum scsi_inq_update_result {
+	SCSI_INQ_UNCHANGED = 0,
+	SCSI_INQ_REPROBE_NEEDED = 1,
+};
+
+int scsi_update_inquiry_data(struct scsi_device *sdev,
+			     unsigned char *inq_result, size_t inq_len);
+
 extern int __must_check scsi_device_get(struct scsi_device *);
 extern void scsi_device_put(struct scsi_device *);
 extern struct scsi_device *scsi_device_lookup(struct Scsi_Host *,
-- 
2.55.0