[PATCH 3.8 66/91] dmi: add support for exact DMI matches in addition to substring matching

[Kamal Mostafa]

3.8.13.13 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jani Nikula <jani.nikula at intel.com>

commit 5017b2851373ee15c7035151853bb1448800cae2 upstream.

dmi_match() considers a substring match to be a successful match.  This is
not always sufficient to distinguish between DMI data for different
systems.  Add support for exact string matching using strcmp() in addition
to the substring matching using strstr().

The specific use case in the i915 driver is to allow us to use an exact
match for D510MO, without also incorrectly matching D510MOV:

  {
	.ident = "Intel D510MO",
	.matches = {
		DMI_MATCH(DMI_BOARD_VENDOR, "Intel"),
		DMI_EXACT_MATCH(DMI_BOARD_NAME, "D510MO"),
	},
  }

Signed-off-by: Jani Nikula <jani.nikula at intel.com>
Cc: <annndddrr at gmail.com>
Cc: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Cornel Panceac <cpanceac at gmail.com>
Acked-by: Daniel Vetter <daniel.vetter at ffwll.ch>
Cc: Greg KH <greg at kroah.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
[ kamal: 3.8-stable prereq for various commits ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/firmware/dmi_scan.c     | 12 +++++++++---
 include/linux/mod_devicetable.h |  6 ++++--
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
index 4cd392d..2861ef4 100644
--- a/drivers/firmware/dmi_scan.c
+++ b/drivers/firmware/dmi_scan.c
@@ -534,9 +534,15 @@ static bool dmi_matches(const struct dmi_system_id *dmi)
 		int s = dmi->matches[i].slot;
 		if (s == DMI_NONE)
 			break;
-		if (dmi_ident[s]
-		    && strstr(dmi_ident[s], dmi->matches[i].substr))
-			continue;
+		if (dmi_ident[s]) {
+			if (!dmi->matches[i].exact_match &&
+			    strstr(dmi_ident[s], dmi->matches[i].substr))
+				continue;
+			else if (dmi->matches[i].exact_match &&
+				 !strcmp(dmi_ident[s], dmi->matches[i].substr))
+				continue;
+		}
+
 		/* No match */
 		return false;
 	}
diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h
index fed3def..163eb82 100644
--- a/include/linux/mod_devicetable.h
+++ b/include/linux/mod_devicetable.h
@@ -480,7 +480,8 @@ enum dmi_field {
 };
 
 struct dmi_strmatch {
-	unsigned char slot;
+	unsigned char slot:7;
+	unsigned char exact_match:1;
 	char substr[79];
 };
 
@@ -508,7 +509,8 @@ struct dmi_system_id {
 #define dmi_device_id dmi_system_id
 #endif
 
-#define DMI_MATCH(a, b)	{ a, b }
+#define DMI_MATCH(a, b)	{ .slot = a, .substr = b }
+#define DMI_EXACT_MATCH(a, b)	{ .slot = a, .substr = b, .exact_match = 1 }
 
 #define PLATFORM_NAME_SIZE	20
 #define PLATFORM_MODULE_PREFIX	"platform:"
-- 
1.8.1.2