lib: vsprintf: Add %pa format specifier for phys_addr_t types

Add the %pa format specifier for printing a phys_addr_t
type and its derivative types (such as resource_size_t),
since the physical address size on some platforms can vary
based on build options, regardless of the native integer
type.

Change-Id: I2ba0003d689a9a2bd13f1a1e2d897b6eacc5d224
Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>

Documentation/printk-formats.txt

@@ -53,6 +53,14 @@ Struct Resources:
 	For printing struct resources. The 'R' and 'r' specifiers result in a
 	printed resource with ('R') or without ('r') a decoded flags member.
 
+Physical addresses:
+
+	%pa	0x01234567 or 0x0123456789abcdef
+
+	For printing a phys_addr_t type (and its derivatives, such as
+	resource_size_t) which can vary based on build options, regardless of
+	the width of the CPU data path. Passed by reference.
+
 MAC/FDDI addresses:
 
 	%pM	00:01:02:03:04:05
@@ -134,9 +142,9 @@ s64 SHOULD be printed with %lld/%llx, (long long):
 	printk("%lld", (long long)s64_var);
 
 If <type> is dependent on a config option for its size (e.g., sector_t,
-blkcnt_t, phys_addr_t, resource_size_t) or is architecture-dependent
-for its size (e.g., tcflag_t), use a format specifier of its largest
-possible type and explicitly cast to it.  Example:
+blkcnt_t) or is architecture-dependent for its size (e.g., tcflag_t), use a
+format specifier of its largest possible type and explicitly cast to it.
+Example:
 
 	printk("test: sector number/total blocks: %llu/%llu\n",
 		(unsigned long long)sector, (unsigned long long)blockcount);

lib/vsprintf.c

@@ -857,6 +857,7 @@ int kptr_restrict __read_mostly;
  *       correctness of the format string and va_list arguments.
  * - 'K' For a kernel pointer that should be hidden from unprivileged users
  * - 'NF' For a netdev_features_t
+ * - 'a' For a phys_addr_t type and its derivative types (passed by reference)
  *
  * Note: The difference between 'S' and 'F' is that on ia64 and ppc64
  * function pointers are really function descriptors, which contain a
@@ -941,6 +942,12 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
 			return netdev_feature_string(buf, end, ptr, spec);
 		}
 		break;
+	case 'a':
+		spec.flags |= SPECIAL | SMALL | ZEROPAD;
+		spec.field_width = sizeof(phys_addr_t) * 2 + 2;
+		spec.base = 16;
+		return number(buf, end,
+			      (unsigned long long) *((phys_addr_t *)ptr), spec);
 	}
 	spec.flags |= SMALL;
 	if (spec.field_width == -1) {