auxdisplay: charlcd: make backlight initial state configurable

The charlcd driver currently flashes the backlight once on init.
This may not be desirable.  Thus, add options for turning the
backlight off or on as well.

Signed-off-by: Mans Rullgard <mans@mansr.com>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>

drivers/auxdisplay/Kconfig

@@ -445,6 +445,27 @@ config PANEL_BOOT_MESSAGE
 	  An empty message will only clear the display at driver init time. Any other
 	  printf()-formatted message is valid with newline and escape codes.
 
+choice
+	prompt "Backlight initial state"
+	default CHARLCD_BL_FLASH
+
+	config CHARLCD_BL_OFF
+		bool "Off"
+		help
+		  Backlight is initially turned off
+
+	config CHARLCD_BL_ON
+		bool "On"
+		help
+		  Backlight is initially turned on
+
+	config CHARLCD_BL_FLASH
+		bool "Flash"
+		help
+		  Backlight is flashed briefly on init
+
+endchoice
+
 endif # AUXDISPLAY
 
 config PANEL

drivers/auxdisplay/charlcd.c

@@ -769,6 +769,14 @@ static void charlcd_puts(struct charlcd *lcd, const char *s)
 #define LCD_INIT_TEXT "Linux-" UTS_RELEASE "\n"
 #endif
 
+#ifdef CONFIG_CHARLCD_BL_ON
+#define LCD_INIT_BL "\x1b[L+"
+#elif defined(CONFIG_CHARLCD_BL_FLASH)
+#define LCD_INIT_BL "\x1b[L*"
+#else
+#define LCD_INIT_BL "\x1b[L-"
+#endif
+
 /* initialize the LCD driver */
 static int charlcd_init(struct charlcd *lcd)
 {
@@ -790,7 +798,7 @@ static int charlcd_init(struct charlcd *lcd)
 		return ret;
 
 	/* display a short message */
-	charlcd_puts(lcd, "\x1b[Lc\x1b[Lb\x1b[L*" LCD_INIT_TEXT);
+	charlcd_puts(lcd, "\x1b[Lc\x1b[Lb" LCD_INIT_BL LCD_INIT_TEXT);
 
 	/* clear the display on the next device opening */
 	priv->must_clear = true;