auxdisplay: Move clear_display to hd44780_common

This moves the clear_display function from charlcd to hd44780_common.
This is one more step to make charlcd independent from device specific
code. The two hd44780 drivers use the new function from hd44780_common
and charlcd calls this function through its function pointer in its ops
structure.
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

@@ -34,8 +34,6 @@
 #define LCD_FLAG_L		0x0080	/* Backlight enabled */
 
 /* LCD commands */
-#define LCD_CMD_DISPLAY_CLEAR	0x01	/* Clear entire display */
-
 #define LCD_CMD_ENTRY_MODE	0x04	/* Set entry mode */
 #define LCD_CMD_CURSOR_INC	0x02	/* Increment cursor */
 
@@ -178,18 +176,6 @@ static void charlcd_clear_fast(struct charlcd *lcd)
 	charlcd_home(lcd);
 }
 
-/* clears the display and resets X/Y */
-static void charlcd_clear_display(struct charlcd *lcd)
-{
-	struct hd44780_common *hdc = lcd->drvdata;
-
-	hdc->write_cmd(hdc, LCD_CMD_DISPLAY_CLEAR);
-	lcd->addr.x = 0;
-	lcd->addr.y = 0;
-	/* we must wait a few milliseconds (15) */
-	long_sleep(15);
-}
-
 static int charlcd_init_display(struct charlcd *lcd)
 {
 	void (*write_cmd_raw)(struct hd44780_common *hdc, int cmd);
@@ -254,7 +240,9 @@ static int charlcd_init_display(struct charlcd *lcd)
 	/* entry mode set : increment, cursor shifting */
 	hdc->write_cmd(hdc, LCD_CMD_ENTRY_MODE | LCD_CMD_CURSOR_INC);
 
-	charlcd_clear_display(lcd);
+	lcd->ops->clear_display(lcd);
+	lcd->addr.x = 0;
+	lcd->addr.y = 0;
 	return 0;
 }
 
@@ -670,8 +658,10 @@ static int charlcd_open(struct inode *inode, struct file *file)
 		goto fail;
 
 	if (priv->must_clear) {
-		charlcd_clear_display(&priv->lcd);
+		priv->lcd.ops->clear_display(&priv->lcd);
 		priv->must_clear = false;
+		priv->lcd.addr.x = 0;
+		priv->lcd.addr.y = 0;
 	}
 	return nonseekable_open(inode, file);
 

drivers/auxdisplay/charlcd.h

@@ -43,6 +43,9 @@ struct charlcd {
  * previously set in addr.x and addr.y by charlcd.
  * @home: Set cursor to 0, 0. The values in addr.x and addr.y are set to 0, 0 by
  * charlcd prior to calling this function.
+ * @clear_display: Again clear the whole display, set the cursor to 0, 0. The
+ * values in addr.x and addr.y are set to 0, 0 by charlcd prior to calling this
+ * function.
  */
 struct charlcd_ops {
 	void (*clear_fast)(struct charlcd *lcd);
@@ -50,6 +53,7 @@ struct charlcd_ops {
 	int (*print)(struct charlcd *lcd, int c);
 	int (*gotoxy)(struct charlcd *lcd);
 	int (*home)(struct charlcd *lcd);
+	int (*clear_display)(struct charlcd *lcd);
 };
 
 struct charlcd *charlcd_alloc(void);

drivers/auxdisplay/hd44780.c

@@ -129,6 +129,7 @@ static const struct charlcd_ops hd44780_ops_gpio8 = {
 	.print		= hd44780_common_print,
 	.gotoxy		= hd44780_common_gotoxy,
 	.home		= hd44780_common_home,
+	.clear_display	= hd44780_common_clear_display,
 };
 
 /* Send a command to the LCD panel in 4 bit GPIO mode */
@@ -175,6 +176,7 @@ static const struct charlcd_ops hd44780_ops_gpio4 = {
 	.print		= hd44780_common_print,
 	.gotoxy		= hd44780_common_gotoxy,
 	.home		= hd44780_common_home,
+	.clear_display	= hd44780_common_clear_display,
 };
 
 static int hd44780_probe(struct platform_device *pdev)

drivers/auxdisplay/hd44780_common.c

 // SPDX-License-Identifier: GPL-2.0-or-later
 #include <linux/module.h>
+#include <linux/sched.h>
 #include <linux/slab.h>
 
 #include "charlcd.h"
 #include "hd44780_common.h"
 
 /* LCD commands */
+#define LCD_CMD_DISPLAY_CLEAR	0x01	/* Clear entire display */
+
 #define LCD_CMD_SET_DDRAM_ADDR	0x80	/* Set display data RAM address */
 
+/* sleeps that many milliseconds with a reschedule */
+static void long_sleep(int ms)
+{
+	schedule_timeout_interruptible(msecs_to_jiffies(ms));
+}
+
 int hd44780_common_print(struct charlcd *lcd, int c)
 {
 	struct hd44780_common *hdc = lcd->drvdata;
@@ -49,6 +58,18 @@ int hd44780_common_home(struct charlcd *lcd)
 }
 EXPORT_SYMBOL_GPL(hd44780_common_home);
 
+/* clears the display and resets X/Y */
+int hd44780_common_clear_display(struct charlcd *lcd)
+{
+	struct hd44780_common *hdc = lcd->drvdata;
+
+	hdc->write_cmd(hdc, LCD_CMD_DISPLAY_CLEAR);
+	/* we must wait a few milliseconds (15) */
+	long_sleep(15);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(hd44780_common_clear_display);
+
 struct hd44780_common *hd44780_common_alloc(void)
 {
 	struct hd44780_common *hd;

drivers/auxdisplay/hd44780_common.h

@@ -17,4 +17,5 @@ struct hd44780_common {
 int hd44780_common_print(struct charlcd *lcd, int c);
 int hd44780_common_gotoxy(struct charlcd *lcd);
 int hd44780_common_home(struct charlcd *lcd);
+int hd44780_common_clear_display(struct charlcd *lcd);
 struct hd44780_common *hd44780_common_alloc(void);

drivers/auxdisplay/panel.c

@@ -877,6 +877,7 @@ static const struct charlcd_ops charlcd_serial_ops = {
 	.backlight	= lcd_backlight,
 	.gotoxy		= hd44780_common_gotoxy,
 	.home		= hd44780_common_home,
+	.clear_display	= hd44780_common_clear_display,
 };
 
 static const struct charlcd_ops charlcd_parallel_ops = {
@@ -884,6 +885,7 @@ static const struct charlcd_ops charlcd_parallel_ops = {
 	.backlight	= lcd_backlight,
 	.gotoxy		= hd44780_common_gotoxy,
 	.home		= hd44780_common_home,
+	.clear_display	= hd44780_common_clear_display,
 };
 
 static const struct charlcd_ops charlcd_tilcd_ops = {
@@ -891,6 +893,7 @@ static const struct charlcd_ops charlcd_tilcd_ops = {
 	.backlight	= lcd_backlight,
 	.gotoxy		= hd44780_common_gotoxy,
 	.home		= hd44780_common_home,
+	.clear_display	= hd44780_common_clear_display,
 };
 
 /* initialize the LCD driver */