nvme: Add a quirk mechanism that uses identify_ctrl

BugLink: https://bugs.launchpad.net/bugs/1664602

Currently, all NVMe quirks are based on PCI IDs.  Add a mechanism to
define quirks based on identify_ctrl's vendor id, model number,
and/or firmware revision.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jens Axboe <axboe@fb.com>
(backported from commit bd4da3ab)
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Acked-By: AceLan Kao <acelan.kao@canonical.com>
Acked-By: Shrirang Bagul <shrirang.bagul@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

drivers/nvme/host/core.c

@@ -879,6 +879,50 @@ static void nvme_set_queue_limits(struct nvme_ctrl *ctrl,
 	blk_queue_virt_boundary(q, ctrl->page_size - 1);
 }
 
+struct nvme_core_quirk_entry {
+	/*
+	 * NVMe model and firmware strings are padded with spaces.  For
+	 * simplicity, strings in the quirk table are padded with NULLs
+	 * instead.
+	 */
+	u16 vid;
+	const char *mn;
+	const char *fr;
+	unsigned long quirks;
+};
+
+static const struct nvme_core_quirk_entry core_quirks[] = {
+};
+
+/* match is null-terminated but idstr is space-padded. */
+static bool string_matches(const char *idstr, const char *match, size_t len)
+{
+	size_t matchlen;
+
+	if (!match)
+		return true;
+
+	matchlen = strlen(match);
+	WARN_ON_ONCE(matchlen > len);
+
+	if (memcmp(idstr, match, matchlen))
+		return false;
+
+	for (; matchlen < len; matchlen++)
+		if (idstr[matchlen] != ' ')
+			return false;
+
+	return true;
+}
+
+static bool quirk_matches(const struct nvme_id_ctrl *id,
+			  const struct nvme_core_quirk_entry *q)
+{
+	return q->vid == le16_to_cpu(id->vid) &&
+		string_matches(id->mn, q->mn, sizeof(id->mn)) &&
+		string_matches(id->fr, q->fr, sizeof(id->fr));
+}
+
 /*
  * Initialize the cached copies of the Identify data and various controller
  * register in our nvme_ctrl structure.  This should be called as soon as
@@ -912,6 +956,24 @@ int nvme_init_identify(struct nvme_ctrl *ctrl)
 		return -EIO;
 	}
 
+	if (!ctrl->identified) {
+		/*
+		 * Check for quirks.  Quirk can depend on firmware version,
+		 * so, in principle, the set of quirks present can change
+		 * across a reset.  As a possible future enhancement, we
+		 * could re-scan for quirks every time we reinitialize
+		 * the device, but we'd have to make sure that the driver
+		 * behaves intelligently if the quirks change.
+		 */
+
+		int i;
+
+		for (i = 0; i < ARRAY_SIZE(core_quirks); i++) {
+			if (quirk_matches(id, &core_quirks[i]))
+				ctrl->quirks |= core_quirks[i].quirks;
+		}
+	}
+
 	ctrl->oncs = le16_to_cpup(&id->oncs);
 	atomic_set(&ctrl->abort_limit, id->acl + 1);
 	ctrl->vwc = id->vwc;
@@ -939,7 +1001,9 @@ int nvme_init_identify(struct nvme_ctrl *ctrl)
 	nvme_set_queue_limits(ctrl, ctrl->admin_q);
 
 	kfree(id);
-	return 0;
+
+	ctrl->identified = true;
+	return ret;
 }
 
 static int nvme_dev_open(struct inode *inode, struct file *file)

drivers/nvme/host/nvme.h

@@ -81,6 +81,7 @@ enum nvme_quirks {
 #define NVME_QUIRK_DELAY_AMOUNT		2000
 
 struct nvme_ctrl {
+	bool identified;
 	const struct nvme_ctrl_ops *ops;
 	struct request_queue *admin_q;
 	struct device *dev;