video: ssd1307fb: Rework the communication functions

To efficiently send a whole page to the display, we need to be able to
manipulate more easily the data arrays that has to be sent to the OLED
controller. As such, this patch introduces a ssd1307fb_array structure
that handles both the small header to be sent over i2c, which contains
the type of information sent, and the raw bytes after that.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

drivers/video/ssd1307fb.c

@@ -51,6 +51,11 @@ struct ssd1307fb_par {
 	u32 width;
 };
 
+struct ssd1307fb_array {
+	u8	type;
+	u8	data[0];
+};
+
 static struct fb_fix_screeninfo ssd1307fb_fix = {
 	.id		= "Solomon SSD1307",
 	.type		= FB_TYPE_PACKED_PIXELS,
@@ -65,49 +70,67 @@ static struct fb_var_screeninfo ssd1307fb_var = {
 	.bits_per_pixel	= 1,
 };
 
-static int ssd1307fb_write_array(struct i2c_client *client, u8 type, u8 *cmd, u32 len)
+static struct ssd1307fb_array *ssd1307fb_alloc_array(u32 len, u8 type)
 {
-	u8 *buf;
-	int ret = 0;
-
-	buf = kzalloc(len + 1, GFP_KERNEL);
-	if (!buf) {
-		dev_err(&client->dev, "Couldn't allocate sending buffer.\n");
-		return -ENOMEM;
-	}
+	struct ssd1307fb_array *array;
 
-	buf[0] = type;
-	memcpy(buf + 1, cmd, len);
+	array = kzalloc(sizeof(struct ssd1307fb_array) + len, GFP_KERNEL);
+	if (!array)
+		return NULL;
 
-	ret = i2c_master_send(client, buf, len + 1);
-	if (ret != len + 1) {
-		dev_err(&client->dev, "Couldn't send I2C command.\n");
-		goto error;
-	}
+	array->type = type;
 
-error:
-	kfree(buf);
-	return ret;
+	return array;
 }
 
-static inline int ssd1307fb_write_cmd_array(struct i2c_client *client, u8 *cmd, u32 len)
+static int ssd1307fb_write_array(struct i2c_client *client,
+				 struct ssd1307fb_array *array, u32 len)
 {
-	return ssd1307fb_write_array(client, SSD1307FB_COMMAND, cmd, len);
+	int ret;
+
+	len += sizeof(struct ssd1307fb_array);
+
+	ret = i2c_master_send(client, (u8 *)array, len);
+	if (ret != len) {
+		dev_err(&client->dev, "Couldn't send I2C command.\n");
+		return ret;
+	}
+
+	return 0;
 }
 
 static inline int ssd1307fb_write_cmd(struct i2c_client *client, u8 cmd)
 {
-	return ssd1307fb_write_cmd_array(client, &cmd, 1);
-}
+	struct ssd1307fb_array *array;
+	int ret;
 
-static inline int ssd1307fb_write_data_array(struct i2c_client *client, u8 *cmd, u32 len)
-{
-	return ssd1307fb_write_array(client, SSD1307FB_DATA, cmd, len);
+	array = ssd1307fb_alloc_array(1, SSD1307FB_COMMAND);
+	if (!array)
+		return -ENOMEM;
+
+	array->data[0] = cmd;
+
+	ret = ssd1307fb_write_array(client, array, 1);
+	kfree(array);
+
+	return ret;
 }
 
 static inline int ssd1307fb_write_data(struct i2c_client *client, u8 data)
 {
-	return ssd1307fb_write_data_array(client, &data, 1);
+	struct ssd1307fb_array *array;
+	int ret;
+
+	array = ssd1307fb_alloc_array(1, SSD1307FB_DATA);
+	if (!array)
+		return -ENOMEM;
+
+	array->data[0] = data;
+
+	ret = ssd1307fb_write_array(client, array, 1);
+	kfree(array);
+
+	return ret;
 }
 
 static void ssd1307fb_update_display(struct ssd1307fb_par *par)