[PATCH 2/4] nvme-core: add a helper to get the len from nid

[Chaitanya Kulkarni]

In the current code we maintain NVME_NIDT_XXX identifier values and the 
their length NVME_NIDT_XXX_LEN separately which has 1:1 mapping. This
adds four extra macros and open coding of such macros in the host and 
the target. Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â 

With this open coding in future we will have to maintain one extra macro
representing length when we add a new NIDT identifier(s).

In this preparation patch add a helper function and use it so that it
can now remove the open coding of the NVME_NIDT_XXX_LEN for host.

Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni at wdc.com>
---
 drivers/nvme/host/core.c | 22 +++++++++++-----------
 include/linux/nvme.h     | 16 ++++++++++++++++
 2 files changed, 27 insertions(+), 11 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index f8a3a36eba86..aac33f575f19 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -1306,38 +1306,38 @@ static int nvme_process_ns_desc(struct nvme_ctrl *ctrl, struct nvme_ns_ids *ids,
 
 	switch (cur->nidt) {
 	case NVME_NIDT_EUI64:
-		if (cur->nidl != NVME_NIDT_EUI64_LEN) {
+		if (cur->nidl != nvme_nidt_len(NVME_NIDT_EUI64)) {
 			dev_warn(ctrl->device, "%s %d for NVME_NIDT_EUI64\n",
 				 warn_str, cur->nidl);
 			return -1;
 		}
-		memcpy(ids->eui64, buf, NVME_NIDT_EUI64_LEN);
-		return NVME_NIDT_EUI64_LEN;
+		memcpy(ids->eui64, buf, nvme_nidt_len(NVME_NIDT_EUI64));
+		return nvme_nidt_len(NVME_NIDT_EUI64);
 	case NVME_NIDT_NGUID:
-		if (cur->nidl != NVME_NIDT_NGUID_LEN) {
+		if (cur->nidl != nvme_nidt_len(NVME_NIDT_NGUID)) {
 			dev_warn(ctrl->device, "%s %d for NVME_NIDT_NGUID\n",
 				 warn_str, cur->nidl);
 			return -1;
 		}
-		memcpy(ids->nguid, buf, NVME_NIDT_NGUID_LEN);
-		return NVME_NIDT_NGUID_LEN;
+		memcpy(ids->nguid, buf, nvme_nidt_len(NVME_NIDT_NGUID));
+		return nvme_nidt_len(NVME_NIDT_NGUID);
 	case NVME_NIDT_UUID:
-		if (cur->nidl != NVME_NIDT_UUID_LEN) {
+		if (cur->nidl != nvme_nidt_len(NVME_NIDT_UUID)) {
 			dev_warn(ctrl->device, "%s %d for NVME_NIDT_UUID\n",
 				 warn_str, cur->nidl);
 			return -1;
 		}
 		uuid_copy(&ids->uuid, buf);
-		return NVME_NIDT_UUID_LEN;
+		return nvme_nidt_len(NVME_NIDT_UUID);
 	case NVME_NIDT_CSI:
-		if (cur->nidl != NVME_NIDT_CSI_LEN) {
+		if (cur->nidl != nvme_nidt_len(NVME_NIDT_CSI)) {
 			dev_warn(ctrl->device, "%s %d for NVME_NIDT_CSI\n",
 				 warn_str, cur->nidl);
 			return -1;
 		}
-		memcpy(&ids->csi, buf, NVME_NIDT_CSI_LEN);
+		memcpy(&ids->csi, buf, nvme_nidt_len(NVME_NIDT_CSI));
 		*csi_seen = true;
-		return NVME_NIDT_CSI_LEN;
+		return nvme_nidt_len(NVME_NIDT_CSI);
 	default:
 		/* Skip unknown types */
 		return cur->nidl;
diff --git a/include/linux/nvme.h b/include/linux/nvme.h
index edcbd60b88b9..5d6b0fe64db1 100644
--- a/include/linux/nvme.h
+++ b/include/linux/nvme.h
@@ -9,6 +9,7 @@
 
 #include <linux/types.h>
 #include <linux/uuid.h>
+#include <linux/kernel.h>
 
 /* NQN names in commands fields specified one size */
 #define NVMF_NQN_FIELD_LEN	256
@@ -497,6 +498,21 @@ enum {
 	NVME_NIDT_CSI		= 0x04,
 };
 
+static inline unsigned int nvme_nidt_len(unsigned int id)
+{
+	static int nvme_nidt_len_map[] = {
+		[NVME_NIDT_EUI64]	= 8,
+		[NVME_NIDT_NGUID]	= 16,
+		[NVME_NIDT_UUID]	= 16,
+		[NVME_NIDT_CSI]		= 1,
+	};
+
+	if (id > ARRAY_SIZE(nvme_nidt_len_map) || !nvme_nidt_len_map[id])
+		return 0;
+
+	return nvme_nidt_len_map[id];
+}
+
 struct nvme_smart_log {
 	__u8			critical_warning;
 	__u8			temperature[2];
-- 
2.22.1