hwmon: applesmc: allow for variable ALV0 and ALV1 package length

On some recent Macbooks, the package length for the light sensors ALV0 and
ALV1 has changed from 6 to 10.  This patch allows for a variable package
length encompassing both variants.

Signed-off-by: Henrik Rydberg <rydberg@euromail.se>
Cc: Nicolas Boichat <nicolas@boichat.ch>
Cc: Riki Oktarianto <rkoktarianto@gmail.com>
Cc: Mark M. Hoffman <mhoffman@lightlink.com>
Cc: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 15 insertions, 5 deletions

diff --git a/drivers/hwmon/applesmc.c b/drivers/hwmon/applesmc.c
index 9a43c4b60ea9..de696b67a4fc 100644
--- a/drivers/hwmon/applesmc.c
+++ b/drivers/hwmon/applesmc.c
@@ -57,8 +57,8 @@
 
 #define KEY_COUNT_KEY           "#KEY" /* r-o ui32 */
 
-#define LIGHT_SENSOR_LEFT_KEY   "ALV0" /* r-o {alv (6 bytes) */
-#define LIGHT_SENSOR_RIGHT_KEY  "ALV1" /* r-o {alv (6 bytes) */
+#define LIGHT_SENSOR_LEFT_KEY   "ALV0" /* r-o {alv (6-10 bytes) */
+#define LIGHT_SENSOR_RIGHT_KEY  "ALV1" /* r-o {alv (6-10 bytes) */
 #define BACKLIGHT_KEY           "LKSB" /* w-o {lkb (2 bytes) */
 
 #define CLAMSHELL_KEY           "MSLD" /* r-o ui8 (unused) */
@@ -543,17 +543,27 @@ out:
 static ssize_t applesmc_light_show(struct device *dev,
                                 struct device_attribute *attr, char *sysfsbuf)
 {
+        static int data_length;
         int ret;
         u8 left = 0, right = 0;
-        u8 buffer[6];
+        u8 buffer[10], query[6];
 
         mutex_lock(&applesmc_lock);
 
-        ret = applesmc_read_key(LIGHT_SENSOR_LEFT_KEY, buffer, 6);
+        if (!data_length) {
+                ret = applesmc_get_key_type(LIGHT_SENSOR_LEFT_KEY, query);
+                if (ret)
+                        goto out;
+                data_length = clamp_val(query[0], 0, 10);
+                printk(KERN_INFO "applesmc: light sensor data length set to "
+                        "%d\n", data_length);
+        }
+
+        ret = applesmc_read_key(LIGHT_SENSOR_LEFT_KEY, buffer, data_length);
         left = buffer[2];
         if (ret)
                 goto out;
-        ret = applesmc_read_key(LIGHT_SENSOR_RIGHT_KEY, buffer, 6);
+        ret = applesmc_read_key(LIGHT_SENSOR_RIGHT_KEY, buffer, data_length);
         right = buffer[2];
 
 out: