drm/fbdev: Clean up fbdev documentation

Rewrite some docs that are not up-to-date any longer. Remove the TODO
item for fbdev-generic conversion, as the helper has been replaced. Make
documentation for DMA, SHMEM and TTM emulation available.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240419083331.7761-44-tzimmermann@suse.de

Documentation/gpu/drm-kms-helpers.rst

@@ -110,15 +110,21 @@ fbdev Helper Functions Reference
 .. kernel-doc:: drivers/gpu/drm/drm_fb_helper.c
    :doc: fbdev helpers
 
+.. kernel-doc:: drivers/gpu/drm/drm_fbdev_dma.c
+   :export:
+
+.. kernel-doc:: drivers/gpu/drm/drm_fbdev_shmem.c
+   :export:
+
+.. kernel-doc:: drivers/gpu/drm/drm_fbdev_ttm.c
+   :export:
+
 .. kernel-doc:: include/drm/drm_fb_helper.h
    :internal:
 
 .. kernel-doc:: drivers/gpu/drm/drm_fb_helper.c
    :export:
 
-.. kernel-doc:: drivers/gpu/drm/drm_fbdev_ttm.c
-   :export:
-
 format Helper Functions Reference
 =================================
 

Documentation/gpu/todo.rst

@@ -243,19 +243,6 @@ Contact: Maintainer of the driver you plan to convert
 
 Level: Intermediate
 
-Convert drivers to use drm_fbdev_generic_setup()
-------------------------------------------------
-
-Most drivers can use drm_fbdev_generic_setup(). Driver have to implement
-atomic modesetting and GEM vmap support. Historically, generic fbdev emulation
-expected the framebuffer in system memory or system-like memory. By employing
-struct iosys_map, drivers with frambuffers in I/O memory can be supported
-as well.
-
-Contact: Maintainer of the driver you plan to convert
-
-Level: Intermediate
-
 Reimplement functions in drm_fbdev_fb_ops without fbdev
 -------------------------------------------------------
 

drivers/gpu/drm/drm_drv.c

@@ -346,7 +346,7 @@ void drm_minor_release(struct drm_minor *minor)
  *		if (ret)
  *			return ret;
  *
- *		drm_fbdev_generic_setup(drm, 32);
+ *		drm_fbdev_{...}_setup(drm, 32);
  *
  *		return 0;
  *	}

drivers/gpu/drm/drm_fb_helper.c

@@ -85,12 +85,8 @@ static DEFINE_MUTEX(kernel_fb_helper_lock);
  * The fb helper functions are useful to provide an fbdev on top of a drm kernel
  * mode setting driver. They can be used mostly independently from the crtc
  * helper functions used by many drivers to implement the kernel mode setting
- * interfaces.
+ * interfaces. Drivers that use one of the shared memory managers, TTM, SHMEM,
- *
+ * DMA, should instead use the corresponding fbdev emulation.
- * Drivers that support a dumb buffer with a virtual address and mmap support,
- * should try out the generic fbdev emulation using drm_fbdev_generic_setup().
- * It will automatically set up deferred I/O if the driver requires a shadow
- * buffer.
  *
  * Existing fbdev implementations should restore the fbdev console by using
  * drm_fb_helper_lastclose() as their &drm_driver.lastclose callback.
@@ -126,9 +122,6 @@ static DEFINE_MUTEX(kernel_fb_helper_lock);
  * atomic context. If drm_fb_helper_deferred_io() is used as the deferred_io
  * callback it will also schedule dirty_work with the damage collected from the
  * mmap page writes.
- *
- * Deferred I/O is not compatible with SHMEM. Such drivers should request an
- * fbdev shadow buffer and call drm_fbdev_generic_setup() instead.
  */
 
 static void drm_fb_helper_restore_lut_atomic(struct drm_crtc *crtc)

include/drm/drm_mode_config.h

@@ -106,8 +106,8 @@ struct drm_mode_config_funcs {
 	 * Drivers implementing fbdev emulation use drm_kms_helper_hotplug_event()
 	 * to call this hook to inform the fbdev helper of output changes.
 	 *
-	 * This hook is deprecated, drivers should instead use
+	 * This hook is deprecated, drivers should instead implement fbdev
-	 * drm_fbdev_generic_setup() which takes care of any necessary
+	 * support with struct drm_client, which takes care of any necessary
 	 * hotplug event forwarding already without further involvement by
 	 * the driver.
 	 */