auxdisplay: hd44780_common_print

We create a hd44780_common_print function. It is derived from the
original charlcd_print. charlcd_print becomes a device independent print
function, that then only calls via its ops function pointers, into the
print function offered by drivers.
Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Lars Poeschel <poeschel@lemonage.de>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

drivers/auxdisplay/charlcd.c

@@ -167,18 +167,15 @@ static void charlcd_home(struct charlcd *lcd)
 
 static void charlcd_print(struct charlcd *lcd, char c)
 {
-	struct hd44780_common *hdc = lcd->drvdata;
+	if (lcd->char_conv)
+		c = lcd->char_conv[(unsigned char)c];
 
-	if (lcd->addr.x < hdc->bwidth) {
-		if (lcd->char_conv)
-			c = lcd->char_conv[(unsigned char)c];
-		hdc->write_data(hdc, c);
+	if (!lcd->ops->print(lcd, c))
 		lcd->addr.x++;
 
-		/* prevents the cursor from wrapping onto the next line */
-		if (lcd->addr.x == hdc->bwidth)
-			charlcd_gotoxy(lcd);
-	}
+	/* prevents the cursor from wrapping onto the next line */
+	if (lcd->addr.x == lcd->width)
+		charlcd_gotoxy(lcd);
 }
 
 static void charlcd_clear_fast(struct charlcd *lcd)
@@ -192,7 +189,7 @@ static void charlcd_clear_fast(struct charlcd *lcd)
 		lcd->ops->clear_fast(lcd);
 	else
 		for (pos = 0; pos < min(2, lcd->height) * hdc->hwidth; pos++)
-			hdc->write_data(hdc, ' ');
+			lcd->ops->print(lcd, ' ');
 
 	charlcd_home(lcd);
 }
@@ -433,12 +430,16 @@ static inline int handle_lcd_special_code(struct charlcd *lcd)
 		processed = 1;
 		break;
 	case 'k': {	/* kill end of line */
-		int x;
+		int x, xs, ys;
 
+		xs = lcd->addr.x;
+		ys = lcd->addr.y;
 		for (x = lcd->addr.x; x < hdc->bwidth; x++)
-			hdc->write_data(hdc, ' ');
+			lcd->ops->print(lcd, ' ');
 
 		/* restore cursor position */
+		lcd->addr.x = xs;
+		lcd->addr.y = ys;
 		charlcd_gotoxy(lcd);
 		processed = 1;
 		break;
@@ -591,7 +592,8 @@ static void charlcd_write_char(struct charlcd *lcd, char c)
 			 * go to the beginning of the next line
 			 */
 			for (; lcd->addr.x < hdc->bwidth; lcd->addr.x++)
-				hdc->write_data(hdc, ' ');
+				lcd->ops->print(lcd, ' ');
+
 			lcd->addr.x = 0;
 			lcd->addr.y = (lcd->addr.y + 1) % lcd->height;
 			charlcd_gotoxy(lcd);

drivers/auxdisplay/charlcd.h

@@ -30,9 +30,21 @@ struct charlcd {
 	void *drvdata;
 };
 
+/**
+ * struct charlcd_ops - Functions used by charlcd. Drivers have to implement
+ * these.
+ * @clear_fast: Clear the whole display and set cursor to position 0, 0.
+ * Optional.
+ * @backlight: Turn backlight on or off. Optional.
+ * @print: Print one character to the display at current cursor position.
+ * The cursor is advanced by charlcd.
+ * The buffered cursor position is advanced by charlcd. The cursor should not
+ * wrap to the next line at the end of a line.
+ */
 struct charlcd_ops {
 	void (*clear_fast)(struct charlcd *lcd);
 	void (*backlight)(struct charlcd *lcd, enum charlcd_onoff on);
+	int (*print)(struct charlcd *lcd, int c);
 };
 
 struct charlcd *charlcd_alloc(void);

drivers/auxdisplay/hd44780.c

@@ -126,6 +126,7 @@ static void hd44780_write_data_gpio8(struct hd44780_common *hdc, int data)
 
 static const struct charlcd_ops hd44780_ops_gpio8 = {
 	.backlight	= hd44780_backlight,
+	.print		= hd44780_common_print,
 };
 
 /* Send a command to the LCD panel in 4 bit GPIO mode */
@@ -169,6 +170,7 @@ static void hd44780_write_data_gpio4(struct hd44780_common *hdc, int data)
 
 static const struct charlcd_ops hd44780_ops_gpio4 = {
 	.backlight	= hd44780_backlight,
+	.print		= hd44780_common_print,
 };
 
 static int hd44780_probe(struct platform_device *pdev)

drivers/auxdisplay/hd44780_common.c

@@ -2,8 +2,22 @@
 #include <linux/module.h>
 #include <linux/slab.h>
 
+#include "charlcd.h"
 #include "hd44780_common.h"
 
+int hd44780_common_print(struct charlcd *lcd, int c)
+{
+	struct hd44780_common *hdc = lcd->drvdata;
+
+	if (lcd->addr.x < hdc->bwidth) {
+		hdc->write_data(hdc, c);
+		return 0;
+	}
+
+	return 1;
+}
+EXPORT_SYMBOL_GPL(hd44780_common_print);
+
 struct hd44780_common *hd44780_common_alloc(void)
 {
 	struct hd44780_common *hd;

drivers/auxdisplay/hd44780_common.h

@@ -14,4 +14,5 @@ struct hd44780_common {
 	void *hd44780;
 };
 
+int hd44780_common_print(struct charlcd *lcd, int c);
 struct hd44780_common *hd44780_common_alloc(void);