drm/fbdev: Add memory-agnostic fbdev client

Add an fbdev client that can work with any memory manager. The
client implementation is the same as existing code in fbdev-dma or
fbdev-shmem.

Provide struct drm_driver.fbdev_probe for the new client to allocate
the surface GEM buffer. The new callback replaces fb_probe of struct
drm_fb_helper_funcs, which does the same.

To use the new client, DRM drivers set fbdev_probe in their struct
drm_driver instance and call drm_fbdev_client_setup(). Probing and
creating the fbdev surface buffer is now independent from the other
operations in struct drm_fb_helper. For the pixel format, the fbdev
client either uses a specified format, the value in preferred_depth
or 32-bit RGB.

v2:
- test for struct drm_fb_helper.funcs for NULL (Sui)
- respect struct drm_mode_config.preferred_depth for default format

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240924071734.98201-4-tzimmermann@suse.de

1 files changed, 9 insertions, 6 deletions

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 550fa69311cb..d5e8994345bb 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -492,8 +492,8 @@ EXPORT_SYMBOL(drm_fb_helper_init);
  * @fb_helper: driver-allocated fbdev helper
  *
  * A helper to alloc fb_info and the member cmap. Called by the driver
- * within the fb_probe fb_helper callback function. Drivers do not
- * need to release the allocated fb_info structure themselves, this is
+ * within the struct &drm_driver.fbdev_probe callback function. Drivers do
+ * not need to release the allocated fb_info structure themselves, this is
  * automatically done when calling drm_fb_helper_fini().
  *
  * RETURNS:
@@ -1612,7 +1612,7 @@ static int drm_fb_helper_find_sizes(struct drm_fb_helper *fb_helper,
 
 /*
  * Allocates the backing storage and sets up the fbdev info structure through
- * the ->fb_probe callback.
+ * the ->fbdev_probe callback.
  */
 static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper)
 {
@@ -1631,7 +1631,10 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper)
 	}
 
 	/* push down into drivers */
-	ret = (*fb_helper->funcs->fb_probe)(fb_helper, &sizes);
+	if (dev->driver->fbdev_probe)
+		ret = dev->driver->fbdev_probe(fb_helper, &sizes);
+	else if (fb_helper->funcs)
+		ret = fb_helper->funcs->fb_probe(fb_helper, &sizes);
 	if (ret < 0)
 		return ret;
 
@@ -1705,7 +1708,7 @@ static void drm_fb_helper_fill_var(struct fb_info *info,
  * instance and the drm framebuffer allocated in &drm_fb_helper.fb.
  *
  * Drivers should call this (or their equivalent setup code) from their
- * &drm_fb_helper_funcs.fb_probe callback after having allocated the fbdev
+ * &drm_driver.fbdev_probe callback after having allocated the fbdev
  * backing storage framebuffer.
  */
 void drm_fb_helper_fill_info(struct fb_info *info,
@@ -1861,7 +1864,7 @@ __drm_fb_helper_initial_config_and_unlock(struct drm_fb_helper *fb_helper)
  * Note that this also registers the fbdev and so allows userspace to call into
  * the driver through the fbdev interfaces.
  *
- * This function will call down into the &drm_fb_helper_funcs.fb_probe callback
+ * This function will call down into the &drm_driver.fbdev_probe callback
  * to let the driver allocate and initialize the fbdev info structure and the
  * drm framebuffer used to back the fbdev. drm_fb_helper_fill_info() is provided
  * as a helper to setup simple default values for the fbdev info structure.