UAPI: ndctl: Fix g++-unsupported initialisation in headers

BugLink: https://bugs.launchpad.net/bugs/1836802
[ Upstream commit 9607871f37dc3e717639694b8d0dc738f2a68efc ]

The following code in the linux/ndctl header file:

	static inline const char *nvdimm_bus_cmd_name(unsigned cmd)
	{
		static const char * const names[] = {
			[ND_CMD_ARS_CAP] = "ars_cap",
			[ND_CMD_ARS_START] = "ars_start",
			[ND_CMD_ARS_STATUS] = "ars_status",
			[ND_CMD_CLEAR_ERROR] = "clear_error",
			[ND_CMD_CALL] = "cmd_call",
		};

		if (cmd < ARRAY_SIZE(names) && names[cmd])
			return names[cmd];
		return "unknown";
	}

is broken in a number of ways:

 (1) ARRAY_SIZE() is not generally defined.

 (2) g++ does not support "non-trivial" array initialisers fully yet.

 (3) Every file that calls this function will acquire a copy of names[].

The same goes for nvdimm_cmd_name().

Fix all three by converting to a switch statement where each case returns a
string.  That way if cmd is a constant, the compiler can trivially reduce it
and, if not, the compiler can use a shared lookup table if it thinks that is
more efficient.

A better way would be to remove these functions and their arrays from the
header entirely.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/include/uapi/linux/ndctl.h b/include/uapi/linux/ndctl.h
index 3f03567631cb092dc8f51aae740dd2a3472730e9..145f242c7c9095dfe5752c717ef308ae820d799c 100644 (file)
--- a/include/uapi/linux/ndctl.h
+++ b/include/uapi/linux/ndctl.h
@@ -176,37 +176,31 @@ enum {
 
 static inline const char *nvdimm_bus_cmd_name(unsigned cmd)
 {
-       static const char * const names[] = {
-               [ND_CMD_ARS_CAP] = "ars_cap",
-               [ND_CMD_ARS_START] = "ars_start",
-               [ND_CMD_ARS_STATUS] = "ars_status",
-               [ND_CMD_CLEAR_ERROR] = "clear_error",
-               [ND_CMD_CALL] = "cmd_call",
-       };
-
-       if (cmd < ARRAY_SIZE(names) && names[cmd])
-               return names[cmd];
-       return "unknown";
+       switch (cmd) {
+       case ND_CMD_ARS_CAP:            return "ars_cap";
+       case ND_CMD_ARS_START:          return "ars_start";
+       case ND_CMD_ARS_STATUS:         return "ars_status";
+       case ND_CMD_CLEAR_ERROR:        return "clear_error";
+       case ND_CMD_CALL:               return "cmd_call";
+       default:                        return "unknown";
+       }
 }
 
 static inline const char *nvdimm_cmd_name(unsigned cmd)
 {
-       static const char * const names[] = {
-               [ND_CMD_SMART] = "smart",
-               [ND_CMD_SMART_THRESHOLD] = "smart_thresh",
-               [ND_CMD_DIMM_FLAGS] = "flags",
-               [ND_CMD_GET_CONFIG_SIZE] = "get_size",
-               [ND_CMD_GET_CONFIG_DATA] = "get_data",
-               [ND_CMD_SET_CONFIG_DATA] = "set_data",
-               [ND_CMD_VENDOR_EFFECT_LOG_SIZE] = "effect_size",
-               [ND_CMD_VENDOR_EFFECT_LOG] = "effect_log",
-               [ND_CMD_VENDOR] = "vendor",
-               [ND_CMD_CALL] = "cmd_call",
-       };
-
-       if (cmd < ARRAY_SIZE(names) && names[cmd])
-               return names[cmd];
-       return "unknown";
+       switch (cmd) {
+       case ND_CMD_SMART:                      return "smart";
+       case ND_CMD_SMART_THRESHOLD:            return "smart_thresh";
+       case ND_CMD_DIMM_FLAGS:                 return "flags";
+       case ND_CMD_GET_CONFIG_SIZE:            return "get_size";
+       case ND_CMD_GET_CONFIG_DATA:            return "get_data";
+       case ND_CMD_SET_CONFIG_DATA:            return "set_data";
+       case ND_CMD_VENDOR_EFFECT_LOG_SIZE:     return "effect_size";
+       case ND_CMD_VENDOR_EFFECT_LOG:          return "effect_log";
+       case ND_CMD_VENDOR:                     return "vendor";
+       case ND_CMD_CALL:                       return "cmd_call";
+       default:                                return "unknown";
+       }
 }
 
 #define ND_IOCTL 'N'