backlight: Allow enable/disable of fb backlights, fixing regressions

Enabling the backlight by default appears to cause problems for many
users. This patch disables backlight controls unless explicitly
enabled by users via a module parameter. Since PMAC users are known
to work, default to enabled in that case.

Signed-off-by: Richard Purdie <rpurdie@rpsys.net>
diff --git a/drivers/video/riva/fbdev.c b/drivers/video/riva/fbdev.c
index f8a3d60..1d1c7c6 100644
--- a/drivers/video/riva/fbdev.c
+++ b/drivers/video/riva/fbdev.c
@@ -215,6 +215,11 @@
 #ifdef CONFIG_MTRR
 static int nomtrr __devinitdata = 0;
 #endif
+#ifdef CONFIG_PMAC_BACKLIGHT
+static int backlight __devinitdata = 1;
+#else
+static int backlight __devinitdata = 0;
+#endif
 
 static char *mode_option __devinitdata = NULL;
 static int  strictmode       = 0;
@@ -2059,7 +2064,10 @@
 	info->monspecs.modedb = NULL;
 
 	pci_set_drvdata(pd, info);
-	riva_bl_init(info->par);
+
+	if (backlight)
+		riva_bl_init(info->par);
+
 	ret = register_framebuffer(info);
 	if (ret < 0) {
 		printk(KERN_ERR PFX
@@ -2157,6 +2165,8 @@
 				forceCRTC = -1;
 		} else if (!strncmp(this_opt, "flatpanel", 9)) {
 			flatpanel = 1;
+		} else if (!strncmp(this_opt, "backlight:", 10)) {
+			backlight = simple_strtoul(this_opt+10, NULL, 0);
 #ifdef CONFIG_MTRR
 		} else if (!strncmp(this_opt, "nomtrr", 6)) {
 			nomtrr = 1;