drm/fb-helper: Perform all fbdev I/O with the same implementation

Implement the fbdev's read/write helpers with the same functions. Use
the generic fbdev's code as template. Convert all drivers.

DRM's fb helpers must implement regular I/O functionality in struct
fb_ops and possibly perform a damage update. Handle all this in the
same functions and convert drivers. The functionality has been used
as part of the generic fbdev code for some time. The drivers don't
set struct drm_fb_helper.fb_dirty, so they will not be affected by
damage handling.

For I/O memory, fb helpers now provide drm_fb_helper_cfb_read() and
drm_fb_helper_cfb_write(). Several drivers require these. Until now
tegra used I/O read and write, although the memory buffer appears to
be in system memory. So use _sys_ helpers now.

v3:
	* fix docs (Javier)
v2:
	* rebase onto vmwgfx changes

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221103151446.2638-18-tzimmermann@suse.de

drivers/gpu/drm/armada/armada_fbdev.c

@@ -19,6 +19,8 @@
 static const struct fb_ops armada_fb_ops = {
 	.owner		= THIS_MODULE,
 	DRM_FB_HELPER_DEFAULT_OPS,
+	.fb_read	= drm_fb_helper_cfb_read,
+	.fb_write	= drm_fb_helper_cfb_write,
 	.fb_fillrect	= drm_fb_helper_cfb_fillrect,
 	.fb_copyarea	= drm_fb_helper_cfb_copyarea,
 	.fb_imageblit	= drm_fb_helper_cfb_imageblit,

drivers/gpu/drm/drm_fb_helper.c

@@ -747,30 +747,132 @@ 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 - wrapper around fb_sys_read
+ * drm_fb_helper_sys_read - Implements struct &fb_ops.fb_read for system memory
  * @info: fb_info struct pointer
  * @buf: userspace buffer to read from framebuffer memory
  * @count: number of bytes to read from framebuffer memory
  * @ppos: read offset within framebuffer memory
  *
- * A wrapper around fb_sys_read implemented by fbdev core
+ * Returns:
+ * The number of bytes read on success, or an error code otherwise.
  */
 ssize_t drm_fb_helper_sys_read(struct fb_info *info, char __user *buf,
 			       size_t count, loff_t *ppos)
 {
-	return fb_sys_read(info, buf, count, ppos);
+	return __drm_fb_helper_read(info, buf, count, ppos, drm_fb_helper_read_screen_buffer);
 }
 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 - wrapper around fb_sys_write
+ * drm_fb_helper_sys_write - Implements struct &fb_ops.fb_write for system memory
  * @info: fb_info struct pointer
  * @buf: userspace buffer to write to framebuffer memory
  * @count: number of bytes to write to framebuffer memory
  * @ppos: write offset within framebuffer memory
  *
- * A wrapper around fb_sys_write implemented by fbdev core
+ * Returns:
+ * The number of bytes written on success, or an error code otherwise.
  */
 ssize_t drm_fb_helper_sys_write(struct fb_info *info, const char __user *buf,
 				size_t count, loff_t *ppos)
@@ -779,7 +881,7 @@ ssize_t drm_fb_helper_sys_write(struct fb_info *info, const char __user *buf,
 	ssize_t ret;
 	struct drm_rect damage_area;
 
-	ret = fb_sys_write(info, buf, count, ppos);
+	ret = __drm_fb_helper_write(info, buf, count, ppos, drm_fb_helper_write_screen_buffer);
 	if (ret <= 0)
 		return ret;
 
@@ -837,6 +939,119 @@ 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
+ * @buf: userspace buffer to read from framebuffer memory
+ * @count: number of bytes to read from framebuffer memory
+ * @ppos: read offset within framebuffer memory
+ *
+ * Returns:
+ * The number of bytes read on success, or an error code otherwise.
+ */
+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);
+}
+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
+ * @buf: userspace buffer to write to framebuffer memory
+ * @count: number of bytes to write to framebuffer memory
+ * @ppos: write offset within framebuffer memory
+ *
+ * Returns:
+ * The number of bytes written on success, or an error code otherwise.
+ */
+ssize_t drm_fb_helper_cfb_write(struct fb_info *info, const char __user *buf,
+				size_t count, loff_t *ppos)
+{
+	loff_t pos = *ppos;
+	ssize_t ret;
+	struct drm_rect damage_area;
+
+	ret = __drm_fb_helper_write(info, buf, count, ppos, fb_write_screen_base);
+	if (ret <= 0)
+		return ret;
+
+	drm_fb_helper_memory_range_to_clip(info, pos, ret, &damage_area);
+	drm_fb_helper_damage(info, damage_area.x1, damage_area.y1,
+			     drm_rect_width(&damage_area),
+			     drm_rect_height(&damage_area));
+
+	return ret;
+}
+EXPORT_SYMBOL(drm_fb_helper_cfb_write);
+
 /**
  * drm_fb_helper_cfb_fillrect - wrapper around cfb_fillrect
  * @info: fbdev registered by the helper
@@ -2183,176 +2398,28 @@ static bool drm_fbdev_use_iomem(struct fb_info *info)
 	return !drm_fbdev_use_shadow_fb(fb_helper) && buffer->map.is_iomem;
 }
 
-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;
-}
-
-static ssize_t fb_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;
-}
-
 static ssize_t drm_fbdev_fb_read(struct fb_info *info, char __user *buf,
 				 size_t count, loff_t *ppos)
 {
-	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);
-
 	if (drm_fbdev_use_iomem(info))
-		ret = fb_read_screen_base(info, buf, count, pos);
+		ret = drm_fb_helper_cfb_read(info, buf, count, ppos);
 	else
-		ret = fb_read_screen_buffer(info, buf, count, pos);
+		ret = drm_fb_helper_sys_read(info, buf, count, ppos);
-
-	if (ret > 0)
-		*ppos += ret;
 
 	return ret;
 }
 
-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;
-}
-
-static ssize_t fb_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;
-}
-
 static ssize_t drm_fbdev_fb_write(struct fb_info *info, const char __user *buf,
 				  size_t count, loff_t *ppos)
 {
-	loff_t pos = *ppos;
-	size_t total_size;
 	ssize_t ret;
-	struct drm_rect damage_area;
-	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.
-	 */
 	if (drm_fbdev_use_iomem(info))
-		ret = fb_write_screen_base(info, buf, count, pos);
+		ret = drm_fb_helper_cfb_write(info, buf, count, ppos);
 	else
-		ret = fb_write_screen_buffer(info, buf, count, pos);
+		ret = drm_fb_helper_sys_write(info, buf, count, ppos);
-
-	if (ret < 0)
-		return ret; /* return last error, if any */
-	else if (!ret)
-		return err; /* return previous error, if any */
-
-	*ppos += ret;
-
-	drm_fb_helper_memory_range_to_clip(info, pos, ret, &damage_area);
-	drm_fb_helper_damage(info, damage_area.x1, damage_area.y1,
-			     drm_rect_width(&damage_area),
-			     drm_rect_height(&damage_area));
 
 	return ret;
 }

drivers/gpu/drm/exynos/exynos_drm_fbdev.c

@@ -49,6 +49,8 @@ static const struct fb_ops exynos_drm_fb_ops = {
 	.owner		= THIS_MODULE,
 	DRM_FB_HELPER_DEFAULT_OPS,
 	.fb_mmap        = exynos_drm_fb_mmap,
+	.fb_read	= drm_fb_helper_cfb_read,
+	.fb_write	= drm_fb_helper_cfb_write,
 	.fb_fillrect	= drm_fb_helper_cfb_fillrect,
 	.fb_copyarea	= drm_fb_helper_cfb_copyarea,
 	.fb_imageblit	= drm_fb_helper_cfb_imageblit,

drivers/gpu/drm/gma500/framebuffer.c

@@ -147,6 +147,8 @@ static const struct fb_ops psbfb_unaccel_ops = {
 	.owner = THIS_MODULE,
 	DRM_FB_HELPER_DEFAULT_OPS,
 	.fb_setcolreg = psbfb_setcolreg,
+	.fb_read = drm_fb_helper_cfb_read,
+	.fb_write = drm_fb_helper_cfb_write,
 	.fb_fillrect = drm_fb_helper_cfb_fillrect,
 	.fb_copyarea = drm_fb_helper_cfb_copyarea,
 	.fb_imageblit = drm_fb_helper_cfb_imageblit,

drivers/gpu/drm/i915/display/intel_fbdev.c

@@ -124,6 +124,8 @@ static const struct fb_ops intelfb_ops = {
 	.owner = THIS_MODULE,
 	DRM_FB_HELPER_DEFAULT_OPS,
 	.fb_set_par = intel_fbdev_set_par,
+	.fb_read = drm_fb_helper_cfb_read,
+	.fb_write = drm_fb_helper_cfb_write,
 	.fb_fillrect = drm_fb_helper_cfb_fillrect,
 	.fb_copyarea = drm_fb_helper_cfb_copyarea,
 	.fb_imageblit = drm_fb_helper_cfb_imageblit,

drivers/gpu/drm/radeon/radeon_fb.c

@@ -80,6 +80,8 @@ static const struct fb_ops radeonfb_ops = {
 	DRM_FB_HELPER_DEFAULT_OPS,
 	.fb_open = radeonfb_open,
 	.fb_release = radeonfb_release,
+	.fb_read = drm_fb_helper_cfb_read,
+	.fb_write = drm_fb_helper_cfb_write,
 	.fb_fillrect = drm_fb_helper_cfb_fillrect,
 	.fb_copyarea = drm_fb_helper_cfb_copyarea,
 	.fb_imageblit = drm_fb_helper_cfb_imageblit,

drivers/gpu/drm/tegra/fb.c

@@ -206,6 +206,8 @@ static int tegra_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
 static const struct fb_ops tegra_fb_ops = {
 	.owner = THIS_MODULE,
 	DRM_FB_HELPER_DEFAULT_OPS,
+	.fb_read = drm_fb_helper_sys_read,
+	.fb_write = drm_fb_helper_sys_write,
 	.fb_fillrect = drm_fb_helper_sys_fillrect,
 	.fb_copyarea = drm_fb_helper_sys_copyarea,
 	.fb_imageblit = drm_fb_helper_sys_imageblit,

include/drm/drm_fb_helper.h

@@ -257,6 +257,11 @@ void drm_fb_helper_sys_copyarea(struct fb_info *info,
 void drm_fb_helper_sys_imageblit(struct fb_info *info,
 				 const struct fb_image *image);
 
+ssize_t drm_fb_helper_cfb_read(struct fb_info *info, char __user *buf,
+			       size_t count, loff_t *ppos);
+ssize_t drm_fb_helper_cfb_write(struct fb_info *info, const char __user *buf,
+				size_t count, loff_t *ppos);
+
 void drm_fb_helper_cfb_fillrect(struct fb_info *info,
 				const struct fb_fillrect *rect);
 void drm_fb_helper_cfb_copyarea(struct fb_info *info,
@@ -402,6 +407,18 @@ static inline void drm_fb_helper_sys_imageblit(struct fb_info *info,
 {
 }
 
+static inline ssize_t drm_fb_helper_cfb_read(struct fb_info *info, char __user *buf,
+					     size_t count, loff_t *ppos)
+{
+	return -ENODEV;
+}
+
+static inline ssize_t drm_fb_helper_cfb_write(struct fb_info *info, const char __user *buf,
+					      size_t count, loff_t *ppos)
+{
+	return -ENODEV;
+}
+
 static inline void drm_fb_helper_cfb_fillrect(struct fb_info *info,
 					      const struct fb_fillrect *rect)
 {