Restrict "Backlight on first keypress" to certain buttons

Allow button-target.h to define the buttons that are filtered by the
"Backlight on first keypress" function.  If left undefined, the
function filters all buttons when the backlight is off.
---
 firmware/drivers/button.c                          |    8 +++++++-
 .../target/arm/as3525/sansa-clip/button-target.h   |    4 ++++
 .../arm/as3525/sansa-clipplus/button-target.h      |    4 ++++
 .../target/arm/as3525/sansa-clipv2/button-target.h |    4 ++++
 4 files changed, 19 insertions(+), 1 deletions(-)

diff --git a/firmware/drivers/button.c b/firmware/drivers/button.c
index c2df006..44e3cc4 100644
--- a/firmware/drivers/button.c
+++ b/firmware/drivers/button.c
@@ -302,6 +302,9 @@ static void button_tick(void)
 #if defined(IRIVER_H100_SERIES) || defined(IRIVER_H300_SERIES)
                             || (remote_type()==REMOTETYPE_H300_NONLCD)
 #endif
+#ifdef BUTTON_BACKLIGHT
+                            || !(btn & BUTTON_BACKLIGHT)
+#endif
                             )
                             button_try_post(btn, data);
                         else
@@ -313,7 +316,10 @@ static void button_tick(void)
 #if BUTTON_REMOTE
                                 || (btn & BUTTON_REMOTE)
 #endif
-                           )
+#ifdef BUTTON_BACKLIGHT
+                                || !(btn & BUTTON_BACKLIGHT)
+#endif
+                            )
                             button_try_post(btn, data);
                         else
                             skip_release = true;
diff --git a/firmware/target/arm/as3525/sansa-clip/button-target.h b/firmware/target/arm/as3525/sansa-clip/button-target.h
index 238fd1d..20694a9 100644
--- a/firmware/target/arm/as3525/sansa-clip/button-target.h
+++ b/firmware/target/arm/as3525/sansa-clip/button-target.h
@@ -56,4 +56,8 @@ bool button_hold(void);
 #define POWEROFF_BUTTON BUTTON_POWER
 #define POWEROFF_COUNT 10
 
+/* Buttons to filter when backlight is off and filter_first_keypress
+   is enabled */
+#define BUTTON_BACKLIGHT BUTTON_HOME
+
 #endif /* _BUTTON_TARGET_H_ */
diff --git a/firmware/target/arm/as3525/sansa-clipplus/button-target.h b/firmware/target/arm/as3525/sansa-clipplus/button-target.h
index c341a94..e5a1227 100644
--- a/firmware/target/arm/as3525/sansa-clipplus/button-target.h
+++ b/firmware/target/arm/as3525/sansa-clipplus/button-target.h
@@ -53,4 +53,8 @@ int button_read_device(void);
 #define POWEROFF_BUTTON BUTTON_POWER
 #define POWEROFF_COUNT 10
 
+/* Buttons to filter when backlight is off and filter_first_keypress
+   is enabled */
+#define BUTTON_BACKLIGHT BUTTON_HOME
+
 #endif /* _BUTTON_TARGET_H_ */
diff --git a/firmware/target/arm/as3525/sansa-clipv2/button-target.h b/firmware/target/arm/as3525/sansa-clipv2/button-target.h
index 238fd1d..20694a9 100644
--- a/firmware/target/arm/as3525/sansa-clipv2/button-target.h
+++ b/firmware/target/arm/as3525/sansa-clipv2/button-target.h
@@ -56,4 +56,8 @@ bool button_hold(void);
 #define POWEROFF_BUTTON BUTTON_POWER
 #define POWEROFF_COUNT 10
 
+/* Buttons to filter when backlight is off and filter_first_keypress
+   is enabled */
+#define BUTTON_BACKLIGHT BUTTON_HOME
+
 #endif /* _BUTTON_TARGET_H_ */
-- 
1.7.1