nvme: expose active quirks in sysfs

Currently, there is no straightforward way for a user to inspect
which quirks are active for a given device from userspace.

Add a new "quirks" sysfs attribute to the nvme controller device.

Reading this file will display a human-readable list
of all active quirks, with each quirk name on a new line.
If no quirks are active, it will display "none".

Tested-by: John Meneghini <jmeneghi@redhat.com>
Reviewed-by: John Meneghini <jmeneghi@redhat.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>

drivers/nvme/host/nvme.h

@@ -180,6 +180,60 @@ enum nvme_quirks {
 	NVME_QUIRK_DMAPOOL_ALIGN_512		= (1 << 22),
 };
 
+static inline char *nvme_quirk_name(enum nvme_quirks q)
+{
+	switch (q) {
+	case NVME_QUIRK_STRIPE_SIZE:
+		return "stripe_size";
+	case NVME_QUIRK_IDENTIFY_CNS:
+		return "identify_cns";
+	case NVME_QUIRK_DEALLOCATE_ZEROES:
+		return "deallocate_zeroes";
+	case NVME_QUIRK_DELAY_BEFORE_CHK_RDY:
+		return "delay_before_chk_rdy";
+	case NVME_QUIRK_NO_APST:
+		return "no_apst";
+	case NVME_QUIRK_NO_DEEPEST_PS:
+		return "no_deepest_ps";
+	case NVME_QUIRK_QDEPTH_ONE:
+		return "qdepth_one";
+	case NVME_QUIRK_MEDIUM_PRIO_SQ:
+		return "medium_prio_sq";
+	case NVME_QUIRK_IGNORE_DEV_SUBNQN:
+		return "ignore_dev_subnqn";
+	case NVME_QUIRK_DISABLE_WRITE_ZEROES:
+		return "disable_write_zeroes";
+	case NVME_QUIRK_SIMPLE_SUSPEND:
+		return "simple_suspend";
+	case NVME_QUIRK_SINGLE_VECTOR:
+		return "single_vector";
+	case NVME_QUIRK_128_BYTES_SQES:
+		return "128_bytes_sqes";
+	case NVME_QUIRK_SHARED_TAGS:
+		return "shared_tags";
+	case NVME_QUIRK_NO_TEMP_THRESH_CHANGE:
+		return "no_temp_thresh_change";
+	case NVME_QUIRK_NO_NS_DESC_LIST:
+		return "no_ns_desc_list";
+	case NVME_QUIRK_DMA_ADDRESS_BITS_48:
+		return "dma_address_bits_48";
+	case NVME_QUIRK_SKIP_CID_GEN:
+		return "skip_cid_gen";
+	case NVME_QUIRK_BOGUS_NID:
+		return "bogus_nid";
+	case NVME_QUIRK_NO_SECONDARY_TEMP_THRESH:
+		return "no_secondary_temp_thresh";
+	case NVME_QUIRK_FORCE_NO_SIMPLE_SUSPEND:
+		return "force_no_simple_suspend";
+	case NVME_QUIRK_BROKEN_MSI:
+		return "broken_msi";
+	case NVME_QUIRK_DMAPOOL_ALIGN_512:
+		return "dmapool_align_512";
+	}
+
+	return "unknown";
+}
+
 /*
  * Common request structure for NVMe passthrough.  All drivers must have
  * this structure as the first member of their request-private data.

drivers/nvme/host/sysfs.c

@@ -601,6 +601,28 @@ static ssize_t dctype_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(dctype);
 
+static ssize_t quirks_show(struct device *dev, struct device_attribute *attr,
+                char *buf)
+{
+	int count = 0, i;
+	struct nvme_ctrl *ctrl = dev_get_drvdata(dev);
+	unsigned long quirks = ctrl->quirks;
+
+	if (!quirks)
+		return sysfs_emit(buf, "none\n");
+
+	for (i = 0; quirks; ++i) {
+		if (quirks & 1) {
+			count += sysfs_emit_at(buf, count, "%s\n",
+					nvme_quirk_name(BIT(i)));
+		}
+		quirks >>= 1;
+	}
+
+	return count;
+}
+static DEVICE_ATTR_RO(quirks);
+
 #ifdef CONFIG_NVME_HOST_AUTH
 static ssize_t nvme_ctrl_dhchap_secret_show(struct device *dev,
 		struct device_attribute *attr, char *buf)
@@ -742,6 +764,7 @@ static struct attribute *nvme_dev_attrs[] = {
 	&dev_attr_kato.attr,
 	&dev_attr_cntrltype.attr,
 	&dev_attr_dctype.attr,
+	&dev_attr_quirks.attr,
 #ifdef CONFIG_NVME_HOST_AUTH
 	&dev_attr_dhchap_secret.attr,
 	&dev_attr_dhchap_ctrl_secret.attr,