staging: panel: fix sparse warnings in lcd_write

This patch fixes two sparse warnings related to lcd_write :
warning: incorrect type in argument 1 (different address spaces)
warning: incorrect type in initializer (incompatible argument 2
(different address spaces))

lcd_write can be used from kernel space (in panel_lcd_print) or from user
space. So we introduce the lcd_write_char function that will write a char to
the device. We modify lcd_write and panel_lcd_print to use it. Finally we add
__user annotation missing in lcd_write.
Signed-off-by: Bastien Armand <armand.bastien@laposte.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/panel/panel.c

@@ -1217,24 +1217,8 @@ static inline int handle_lcd_special_code(void)
 	return processed;
 }
 
-static ssize_t lcd_write(struct file *file,
-			 const char *buf, size_t count, loff_t *ppos)
+static void lcd_write_char(char c)
 {
-	const char *tmp = buf;
-	char c;
-
-	for (; count-- > 0; (ppos ? (*ppos)++ : 0), ++tmp) {
-		if (!in_interrupt() && (((count + 1) & 0x1f) == 0))
-			/* let's be a little nice with other processes
-			   that need some CPU */
-			schedule();
-
-		if (ppos == NULL && file == NULL)
-			/* let's not use get_user() from the kernel ! */
-			c = *tmp;
-		else if (get_user(c, tmp))
-			return -EFAULT;
-
 	/* first, we'll test if we're in escape mode */
 	if ((c != '\n') && lcd_escape_len >= 0) {
 		/* yes, let's add this char to the buffer */
@@ -1322,6 +1306,24 @@ static ssize_t lcd_write(struct file *file,
 		if (processed || (lcd_escape_len >= LCD_ESCAPE_LEN))
 			lcd_escape_len = -1;
 	} /* escape codes */
+}
+
+static ssize_t lcd_write(struct file *file,
+	const char __user *buf, size_t count, loff_t *ppos)
+{
+	const char __user *tmp = buf;
+	char c;
+
+	for (; count-- > 0; (*ppos)++, tmp++) {
+		if (!in_interrupt() && (((count + 1) & 0x1f) == 0))
+			/* let's be a little nice with other processes
+			   that need some CPU */
+			schedule();
+
+		if (get_user(c, buf))
+			return -EFAULT;
+
+		lcd_write_char(c);
 	}
 
 	return tmp - buf;
@@ -1365,8 +1367,19 @@ static struct miscdevice lcd_dev = {
 /* public function usable from the kernel for any purpose */
 static void panel_lcd_print(const char *s)
 {
-	if (lcd_enabled && lcd_initialized)
-		lcd_write(NULL, s, strlen(s), NULL);
+	const char *tmp = s;
+	int count = strlen(s);
+
+	if (lcd_enabled && lcd_initialized) {
+		for (; count-- > 0; tmp++) {
+			if (!in_interrupt() && (((count + 1) & 0x1f) == 0))
+				/* let's be a little nice with other processes
+				   that need some CPU */
+				schedule();
+
+			lcd_write_char(*tmp);
+		}
+	}
 }
 
 /* initialize the LCD driver */