powerpc/pseries: Read common partition via pstore

This patch exploits pstore subsystem to read details of common partition
in NVRAM to a separate file in /dev/pstore. For instance, common partition
details will be stored in a file named [common-nvram-6].

Signed-off-by: Aruna Balakrishnaiah <aruna@linux.vnet.ibm.com>
Reviewed-by: Jim Keniston <jkenisto@us.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/platforms/pseries/nvram.c b/arch/powerpc/platforms/pseries/nvram.c
index f7392f6..14cc486 100644
--- a/arch/powerpc/platforms/pseries/nvram.c
+++ b/arch/powerpc/platforms/pseries/nvram.c
@@ -138,10 +138,17 @@
 	.os_partition = false
 };
 
+static struct nvram_os_partition common_partition = {
+	.name = "common",
+	.index = -1,
+	.os_partition = false
+};
+
 static enum pstore_type_id nvram_type_ids[] = {
 	PSTORE_TYPE_DMESG,
 	PSTORE_TYPE_PPC_RTAS,
 	PSTORE_TYPE_PPC_OF,
+	PSTORE_TYPE_PPC_COMMON,
 	-1
 };
 static int read_type;
@@ -530,7 +537,7 @@
 }
 
 /*
- * Reads the oops/panic report, rtas and of-config partition.
+ * Reads the oops/panic report, rtas, of-config and common partition.
  * Returns the length of the data we read from each partition.
  * Returns 0 if we've been called before.
  */
@@ -566,6 +573,14 @@
 		time->tv_sec = 0;
 		time->tv_nsec = 0;
 		break;
+	case PSTORE_TYPE_PPC_COMMON:
+		sig = NVRAM_SIG_SYS;
+		part = &common_partition;
+		*type = PSTORE_TYPE_PPC_COMMON;
+		*id = PSTORE_TYPE_PPC_COMMON;
+		time->tv_sec = 0;
+		time->tv_nsec = 0;
+		break;
 	default:
 		return 0;
 	}