drm/fb_helper: Create wrappers for fb_sys_read/write funcs

Some drm drivers populate their fb_ops with fb_sys_read/write fb sysfs
ops.

Create a drm_fb_helper function that wraps around these calls.

This is part of an effort to prevent drm drivers from calling fbdev
functions directly, in order to make fbdev emulation a top level drm
option.

v3:
- Fix kerneldoc errors

v2:
- Added kerneldocs
- Follow the drm way of aligning of arguments in func definitions
- Remove unnecessary checks for non NULL fb_info

Signed-off-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

3 files changed, 38 insertions, 0 deletions

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index c46ca311d8c3..6ab503b387db 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -37,6 +37,7 @@ config DRM_KMS_FB_HELPER
 	select FB
 	select FRAMEBUFFER_CONSOLE if !EXPERT
 	select FRAMEBUFFER_CONSOLE_DETECT_PRIMARY if FRAMEBUFFER_CONSOLE
+	select FB_SYS_FOPS
 	help
 	  FBDEV helpers for KMS drivers.
 
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 5383c3f7d0ec..39f3be2f37a2 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -761,6 +761,38 @@ void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper)
 }
 EXPORT_SYMBOL(drm_fb_helper_unlink_fbi);
 
+/**
+ * drm_fb_helper_sys_read - wrapper around fb_sys_read
+ * @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
+ */
+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);
+}
+EXPORT_SYMBOL(drm_fb_helper_sys_read);
+
+/**
+ * drm_fb_helper_sys_write - wrapper around fb_sys_write
+ * @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
+ */
+ssize_t drm_fb_helper_sys_write(struct fb_info *info, const char __user *buf,
+				size_t count, loff_t *ppos)
+{
+	return fb_sys_write(info, buf, count, ppos);
+}
+EXPORT_SYMBOL(drm_fb_helper_sys_write);
+
 static int setcolreg(struct drm_crtc *crtc, u16 red, u16 green,
 		     u16 blue, u16 regno, struct fb_info *info)
 {
diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h
index 4c908370a61e..fc123685baf4 100644
--- a/include/drm/drm_fb_helper.h
+++ b/include/drm/drm_fb_helper.h
@@ -147,6 +147,11 @@ void drm_fb_helper_fill_fix(struct fb_info *info, uint32_t pitch,
 
 void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper);
 
+ssize_t drm_fb_helper_sys_read(struct fb_info *info, char __user *buf,
+			       size_t count, loff_t *ppos);
+ssize_t drm_fb_helper_sys_write(struct fb_info *info, const char __user *buf,
+				size_t count, loff_t *ppos);
+
 int drm_fb_helper_setcmap(struct fb_cmap *cmap, struct fb_info *info);
 
 int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper);