fbdev/ssd1307fb: Generate deferred I/O ops

Use the existing generator macros to create deferred-I/O helpers
for ssd1307fb and set them in the fb_ops structure. Functions
for damage handling on memory ranges and areas are provided by
the driver.

Ssd1307fb's implementation of fb_write writes to system memory,
so the generated code can use the respective helper internally.
This also fixes a long-standing bug where fb_write returned an
errno code instead of the number of written bytes. See the commit
message of commit 921b738 ("fbdev: Return number of bytes
read or written") for more details.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Helge Deller <deller@gmx.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20230706151432.20674-9-tzimmermann@suse.de

Author: tdz

drivers/video/fbdev/ssd1307fb.c

@@ -292,43 +292,6 @@ static int ssd1307fb_update_display(struct ssd1307fb_par *par)
 	return ssd1307fb_update_rect(par, 0, 0, par->width, par->height);
 }
 
-static ssize_t ssd1307fb_write(struct fb_info *info, const char __user *buf,
-		size_t count, loff_t *ppos)
-{
-	struct ssd1307fb_par *par = info->par;
-	unsigned long total_size;
-	unsigned long p = *ppos;
-	void *dst;
-	int ret;
-
-	if (!info->screen_buffer)
-		return -ENODEV;
-
-	total_size = info->fix.smem_len;
-
-	if (p > total_size)
-		return -EINVAL;
-
-	if (count + p > total_size)
-		count = total_size - p;
-
-	if (!count)
-		return -EINVAL;
-
-	dst = info->screen_buffer + p;
-
-	if (copy_from_user(dst, buf, count))
-		return -EFAULT;
-
-	ret = ssd1307fb_update_display(par);
-	if (ret < 0)
-		return ret;
-
-	*ppos += count;
-
-	return count;
-}
-
 static int ssd1307fb_blank(int blank_mode, struct fb_info *info)
 {
 	struct ssd1307fb_par *par = info->par;
@@ -339,39 +302,29 @@ static int ssd1307fb_blank(int blank_mode, struct fb_info *info)
 		return ssd1307fb_write_cmd(par->client, SSD1307FB_DISPLAY_ON);
 }
 
-static void ssd1307fb_fillrect(struct fb_info *info, const struct fb_fillrect *rect)
+static void ssd1307fb_defio_damage_range(struct fb_info *info, off_t off, size_t len)
 {
 	struct ssd1307fb_par *par = info->par;
-	sys_fillrect(info, rect);
-	ssd1307fb_update_rect(par, rect->dx, rect->dy, rect->width,
-			      rect->height);
-}
 
-static void ssd1307fb_copyarea(struct fb_info *info, const struct fb_copyarea *area)
-{
-	struct ssd1307fb_par *par = info->par;
-	sys_copyarea(info, area);
-	ssd1307fb_update_rect(par, area->dx, area->dy, area->width,
-			      area->height);
+	ssd1307fb_update_display(par);
 }
 
-static void ssd1307fb_imageblit(struct fb_info *info, const struct fb_image *image)
+static void ssd1307fb_defio_damage_area(struct fb_info *info, u32 x, u32 y,
+					u32 width, u32 height)
 {
 	struct ssd1307fb_par *par = info->par;
-	sys_imageblit(info, image);
-	ssd1307fb_update_rect(par, image->dx, image->dy, image->width,
-			      image->height);
+
+	ssd1307fb_update_rect(par, x, y, width, height);
 }
 
+FB_GEN_DEFAULT_DEFERRED_SYS_OPS(ssd1307fb,
+				ssd1307fb_defio_damage_range,
+				ssd1307fb_defio_damage_area)
+
 static const struct fb_ops ssd1307fb_ops = {
 	.owner		= THIS_MODULE,
-	.fb_read	= fb_sys_read,
-	.fb_write	= ssd1307fb_write,
+	FB_DEFAULT_DEFERRED_OPS(ssd1307fb),
 	.fb_blank	= ssd1307fb_blank,
-	.fb_fillrect	= ssd1307fb_fillrect,
-	.fb_copyarea	= ssd1307fb_copyarea,
-	.fb_imageblit	= ssd1307fb_imageblit,
-	.fb_mmap	= fb_deferred_io_mmap,
 };
 
 static void ssd1307fb_deferred_io(struct fb_info *info, struct list_head *pagereflist)