drm/fb-helper: Use fb_{cfb,sys}_{read, write}()

Implement DRM fbdev helpers for reading and writing framebuffer
memory with the respective fbdev functions. Removes duplicate
code.

v2:
	* rename fb_cfb_() to fb_io_() (Geert)
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Tested-by: Sui Jingfeng <suijingfeng@loongson.cn>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Acked-by: Helge Deller <deller@gmx.de>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230428122452.4856-20-tzimmermann@suse.de

drivers/gpu/drm/drm_fb_helper.c

@@ -706,95 +706,6 @@ void drm_fb_helper_deferred_io(struct fb_info *info, struct list_head *pagerefli
 }
 EXPORT_SYMBOL(drm_fb_helper_deferred_io);
 
-typedef ssize_t (*drm_fb_helper_read_screen)(struct fb_info *info, char __user *buf,
-					     size_t count, loff_t pos);
-
-static ssize_t __drm_fb_helper_read(struct fb_info *info, char __user *buf, size_t count,
-				    loff_t *ppos, drm_fb_helper_read_screen read_screen)
-{
-	loff_t pos = *ppos;
-	size_t total_size;
-	ssize_t ret;
-
-	if (info->screen_size)
-		total_size = info->screen_size;
-	else
-		total_size = info->fix.smem_len;
-
-	if (pos >= total_size)
-		return 0;
-	if (count >= total_size)
-		count = total_size;
-	if (total_size - count < pos)
-		count = total_size - pos;
-
-	if (info->fbops->fb_sync)
-		info->fbops->fb_sync(info);
-
-	ret = read_screen(info, buf, count, pos);
-	if (ret > 0)
-		*ppos += ret;
-
-	return ret;
-}
-
-typedef ssize_t (*drm_fb_helper_write_screen)(struct fb_info *info, const char __user *buf,
-					      size_t count, loff_t pos);
-
-static ssize_t __drm_fb_helper_write(struct fb_info *info, const char __user *buf, size_t count,
-				     loff_t *ppos, drm_fb_helper_write_screen write_screen)
-{
-	loff_t pos = *ppos;
-	size_t total_size;
-	ssize_t ret;
-	int err = 0;
-
-	if (info->screen_size)
-		total_size = info->screen_size;
-	else
-		total_size = info->fix.smem_len;
-
-	if (pos > total_size)
-		return -EFBIG;
-	if (count > total_size) {
-		err = -EFBIG;
-		count = total_size;
-	}
-	if (total_size - count < pos) {
-		if (!err)
-			err = -ENOSPC;
-		count = total_size - pos;
-	}
-
-	if (info->fbops->fb_sync)
-		info->fbops->fb_sync(info);
-
-	/*
-	 * Copy to framebuffer even if we already logged an error. Emulates
-	 * the behavior of the original fbdev implementation.
-	 */
-	ret = write_screen(info, buf, count, pos);
-	if (ret < 0)
-		return ret; /* return last error, if any */
-	else if (!ret)
-		return err; /* return previous error, if any */
-
-	*ppos += ret;
-
-	return ret;
-}
-
-static ssize_t drm_fb_helper_read_screen_buffer(struct fb_info *info, char __user *buf,
-						size_t count, loff_t pos)
-{
-	const char *src = info->screen_buffer + pos;
-
-	if (copy_to_user(buf, src, count))
-		return -EFAULT;
-
-	return count;
-}
-
 /**
  * drm_fb_helper_sys_read - Implements struct &fb_ops.fb_read for system memory
  * @info: fb_info struct pointer
@@ -808,21 +719,10 @@ static ssize_t drm_fb_helper_read_screen_buffer(struct fb_info *info, char __use
 ssize_t drm_fb_helper_sys_read(struct fb_info *info, char __user *buf,
 			       size_t count, loff_t *ppos)
 {
-	return __drm_fb_helper_read(info, buf, count, ppos, drm_fb_helper_read_screen_buffer);
+	return fb_sys_read(info, buf, count, ppos);
 }
 EXPORT_SYMBOL(drm_fb_helper_sys_read);
 
-static ssize_t drm_fb_helper_write_screen_buffer(struct fb_info *info, const char __user *buf,
-						 size_t count, loff_t pos)
-{
-	char *dst = info->screen_buffer + pos;
-
-	if (copy_from_user(dst, buf, count))
-		return -EFAULT;
-
-	return count;
-}
-
 /**
  * drm_fb_helper_sys_write - Implements struct &fb_ops.fb_write for system memory
  * @info: fb_info struct pointer
@@ -841,7 +741,7 @@ ssize_t drm_fb_helper_sys_write(struct fb_info *info, const char __user *buf,
 	ssize_t ret;
 	struct drm_rect damage_area;
 
-	ret = __drm_fb_helper_write(info, buf, count, ppos, drm_fb_helper_write_screen_buffer);
+	ret = fb_sys_write(info, buf, count, ppos);
 	if (ret <= 0)
 		return ret;
 
@@ -913,39 +813,6 @@ void drm_fb_helper_sys_imageblit(struct fb_info *info,
 }
 EXPORT_SYMBOL(drm_fb_helper_sys_imageblit);
 
-static ssize_t fb_read_screen_base(struct fb_info *info, char __user *buf, size_t count,
-				   loff_t pos)
-{
-	const char __iomem *src = info->screen_base + pos;
-	size_t alloc_size = min_t(size_t, count, PAGE_SIZE);
-	ssize_t ret = 0;
-	int err = 0;
-	char *tmp;
-
-	tmp = kmalloc(alloc_size, GFP_KERNEL);
-	if (!tmp)
-		return -ENOMEM;
-
-	while (count) {
-		size_t c = min_t(size_t, count, alloc_size);
-
-		memcpy_fromio(tmp, src, c);
-		if (copy_to_user(buf, tmp, c)) {
-			err = -EFAULT;
-			break;
-		}
-
-		src += c;
-		buf += c;
-		ret += c;
-		count -= c;
-	}
-
-	kfree(tmp);
-
-	return ret ? ret : err;
-}
-
 /**
  * drm_fb_helper_cfb_read - Implements struct &fb_ops.fb_read for I/O memory
  * @info: fb_info struct pointer
@@ -959,43 +826,10 @@ static ssize_t fb_read_screen_base(struct fb_info *info, char __user *buf, size_
 ssize_t drm_fb_helper_cfb_read(struct fb_info *info, char __user *buf,
 			       size_t count, loff_t *ppos)
 {
-	return __drm_fb_helper_read(info, buf, count, ppos, fb_read_screen_base);
+	return fb_io_read(info, buf, count, ppos);
 }
 EXPORT_SYMBOL(drm_fb_helper_cfb_read);
 
-static ssize_t fb_write_screen_base(struct fb_info *info, const char __user *buf, size_t count,
-				    loff_t pos)
-{
-	char __iomem *dst = info->screen_base + pos;
-	size_t alloc_size = min_t(size_t, count, PAGE_SIZE);
-	ssize_t ret = 0;
-	int err = 0;
-	u8 *tmp;
-
-	tmp = kmalloc(alloc_size, GFP_KERNEL);
-	if (!tmp)
-		return -ENOMEM;
-
-	while (count) {
-		size_t c = min_t(size_t, count, alloc_size);
-
-		if (copy_from_user(tmp, buf, c)) {
-			err = -EFAULT;
-			break;
-		}
-		memcpy_toio(dst, tmp, c);
-
-		dst += c;
-		buf += c;
-		ret += c;
-		count -= c;
-	}
-
-	kfree(tmp);
-
-	return ret ? ret : err;
-}
-
 /**
  * drm_fb_helper_cfb_write - Implements struct &fb_ops.fb_write for I/O memory
  * @info: fb_info struct pointer
@@ -1014,7 +848,7 @@ ssize_t drm_fb_helper_cfb_write(struct fb_info *info, const char __user *buf,
 	ssize_t ret;
 	struct drm_rect damage_area;
 
-	ret = __drm_fb_helper_write(info, buf, count, ppos, fb_write_screen_base);
+	ret = fb_io_write(info, buf, count, ppos);
 	if (ret <= 0)
 		return ret;