ACPI: thinkpad-acpi: fix brightness_set error paths

The code calling brightness_set() can't handle EINTR/ERESTARTSYS well, nor
is it checking brightness_set() return status properly.

Fix it.

Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 21 insertions, 13 deletions

diff --git a/drivers/misc/thinkpad_acpi.c b/drivers/misc/thinkpad_acpi.c
index 306daa524c03..8c9430775285 100644
--- a/drivers/misc/thinkpad_acpi.c
+++ b/drivers/misc/thinkpad_acpi.c
@@ -3278,6 +3278,8 @@ static void brightness_exit(void)
 
 static int brightness_update_status(struct backlight_device *bd)
 {
+        /* it is the backlight class's job (caller) to handle
+         * EINTR and other errors properly */
         return brightness_set(
                 (bd->props.fb_blank == FB_BLANK_UNBLANK &&
                  bd->props.power == FB_BLANK_UNBLANK) ?
@@ -3318,6 +3320,7 @@ static int brightness_get(struct backlight_device *bd)
         return level;
 }
 
+/* May return EINTR which can always be mapped to ERESTARTSYS */
 static int brightness_set(int value)
 {
         int cmos_cmd, inc, i, res;
@@ -3381,29 +3384,34 @@ static int brightness_read(char *p)
 static int brightness_write(char *buf)
 {
         int level;
-        int new_level;
+        int rc;
         char *cmd;
         int max_level = (tp_features.bright_16levels) ? 15 : 7;
 
-        while ((cmd = next_cmd(&buf))) {
-                if ((level = brightness_get(NULL)) < 0)
-                        return level;
+        level = brightness_get(NULL);
+        if (level < 0)
+                return level;
 
+        while ((cmd = next_cmd(&buf))) {
                 if (strlencmp(cmd, "up") == 0) {
-                        new_level = level == (max_level)?
-                                                max_level : level + 1;
+                        if (level < max_level)
+                                level++;
                 } else if (strlencmp(cmd, "down") == 0) {
-                        new_level = level == 0? 0 : level - 1;
-                } else if (sscanf(cmd, "level %d", &new_level) == 1 &&
-                           new_level >= 0 && new_level <= max_level) {
-                        /* new_level set */
+                        if (level > 0)
+                                level--;
+                } else if (sscanf(cmd, "level %d", &level) == 1 &&
+                           level >= 0 && level <= max_level) {
+                        /* new level set */
                 } else
                         return -EINVAL;
-
-                brightness_set(new_level);
         }
 
-        return 0;
+        /*
+         * Now we know what the final level should be, so we try to set it.
+         * Doing it this way makes the syscall restartable in case of EINTR
+         */
+        rc = brightness_set(level);
+        return (rc == -EINTR)? ERESTARTSYS : rc;
 }
 
 static struct ibm_struct brightness_driver_data = {