drm: Add client-agnostic setup helper

DRM may support multiple in-kernel clients that run as soon as a DRM
driver has been registered. To select the client(s) in a single place,
introduce drm_client_setup().

Drivers that call the new helper automatically instantiate the kernel's
configured default clients. Only fbdev emulation is currently supported.
Later versions can add support for DRM-based logging, a boot logo or even
a console.

Some drivers handle the color mode for clients internally. Provide the
helper drm_client_setup_with_color_mode() for them.

Using the new interface requires the driver to select
DRM_CLIENT_SELECTION in its Kconfig. For now this only enables the
client-setup helpers if the fbdev client has been configured by the
user. A future patchset will further modularize client support and
rework DRM_CLIENT_SELECTION to select the correct dependencies for
all its clients.

v5:
- add CONFIG_DRM_CLIENT_SELECTION und DRM_CLIENT_SETUP
v4:
- fix docs for drm_client_setup_with_fourcc() (Geert)
v3:
- fix build error
v2:
- add drm_client_setup_with_fourcc() (Laurent)
- push default-format handling into actual clients

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240924071734.98201-5-tzimmermann@suse.de

1 files changed, 12 insertions, 0 deletions

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 1cb5a4f19293..f045ff0e8c99 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -210,6 +210,18 @@ config DRM_DEBUG_MODESET_LOCK
 
 	  If in doubt, say "N".
 
+config DRM_CLIENT_SELECTION
+	bool
+	depends on DRM
+	select DRM_CLIENT_SETUP if DRM_FBDEV_EMULATION
+	help
+	  Drivers that support in-kernel DRM clients have to select this
+	  option.
+
+config DRM_CLIENT_SETUP
+	bool
+	depends on DRM_CLIENT_SELECTION
+
 config DRM_FBDEV_EMULATION
 	bool "Enable legacy fbdev support for your modesetting driver"
 	depends on DRM