drm/client: Add client-lib module

Add drm_client_lib.ko to contain DRM's built-in client. Move the
existing client for fbdev emulation into the new module. Protect the
new module behind CONFIG_DRM_CLIENT_LIB.

The Kconfig rules separate the DRM drivers from the DRM clients. A
driver can opt into the default clients, but the user configures
each client individually. To do so, DRM drivers still select
DRM_CLIENT_SELECTION. The option is now a tristate that further
selects all dependencies of the enabled DRM clients. There's
a menu option for each client. Enabling at least one client also
selects DRM_CLIENT_SETUP, so that drivers call drm_client_setup().
New DRM clients should depend on DRM_CLIENT_SELECTION.

There are existing kernel options in drm_fb_helper.o, so leave this
file in the KMS-helper module for now.

v5:
- leave fbdev helpers in drm_kms_helper.ko for now
v3:
- fix commit changelog
v2:
- keep client code in core
- protect lib with DRM_CLIENT_LIB
- remove duplicate line from Makefile (Jocelyn)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241014085740.582287-13-tzimmermann@suse.de

drivers/gpu/drm/Kconfig

@@ -9,8 +9,6 @@ menuconfig DRM
 	tristate "Direct Rendering Manager (XFree86 4.1.0 and higher DRI support)"
 	depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && HAS_DMA
 	select DRM_PANEL_ORIENTATION_QUIRKS
-	select DRM_KMS_HELPER if DRM_FBDEV_EMULATION
-	select FB_CORE if DRM_FBDEV_EMULATION
 	select HDMI
 	select I2C
 	select DMA_SHARED_BUFFER
@@ -219,10 +217,19 @@ config DRM_CLIENT
 	  option. Drivers that support the default clients should
 	  select DRM_CLIENT_SELECTION instead.
 
-config DRM_CLIENT_SELECTION
-	bool
+config DRM_CLIENT_LIB
+	tristate
 	depends on DRM
-	select DRM_CLIENT_SETUP if DRM_FBDEV_EMULATION
+	select DRM_KMS_HELPER if DRM_FBDEV_EMULATION
+	select FB_CORE if DRM_FBDEV_EMULATION
+	help
+	  This option enables the DRM client library and selects all
+	  modules and components according to the enabled clients.
+
+config DRM_CLIENT_SELECTION
+	tristate
+	depends on DRM
+	select DRM_CLIENT_LIB if DRM_FBDEV_EMULATION
 	help
 	  Drivers that support in-kernel DRM clients have to select this
 	  option.
@@ -230,11 +237,18 @@ config DRM_CLIENT_SELECTION
 config DRM_CLIENT_SETUP
 	bool
 	depends on DRM_CLIENT_SELECTION
+	help
+	  Enables the DRM client selection. DRM drivers that support the
+	  default clients should select DRM_CLIENT_SELECTION instead.
+
+menu "Supported DRM clients"
+	depends on DRM_CLIENT_SELECTION
 
 config DRM_FBDEV_EMULATION
 	bool "Enable legacy fbdev support for your modesetting driver"
-	depends on DRM
+	depends on DRM_CLIENT_SELECTION
 	select DRM_CLIENT
+	select DRM_CLIENT_SETUP
 	select FRAMEBUFFER_CONSOLE_DETECT_PRIMARY if FRAMEBUFFER_CONSOLE
 	default FB
 	help
@@ -273,6 +287,8 @@ config DRM_FBDEV_LEAK_PHYS_SMEM
 	  If in doubt, say "N" or spread the word to your closed source
 	  library vendor.
 
+endmenu
+
 config DRM_LOAD_EDID_FIRMWARE
 	bool "Allow to specify an EDID data set instead of probing for it"
 	depends on DRM

drivers/gpu/drm/Makefile

@@ -144,14 +144,18 @@ drm_kms_helper-y := \
 	drm_probe_helper.o \
 	drm_self_refresh_helper.o \
 	drm_simple_kms_helper.o
-drm_kms_helper-$(CONFIG_DRM_CLIENT_SETUP) += \
-	drm_client_setup.o
 drm_kms_helper-$(CONFIG_DRM_PANEL_BRIDGE) += bridge/panel.o
-drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += \
-	drm_fbdev_client.o \
-	drm_fb_helper.o
+drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o
 obj-$(CONFIG_DRM_KMS_HELPER) += drm_kms_helper.o
 
+#
+# DRM clients
+#
+
+drm_client_lib-y := drm_client_setup.o
+drm_client_lib-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fbdev_client.o
+obj-$(CONFIG_DRM_CLIENT_LIB) += drm_client_lib.o
+
 #
 # Drivers and the rest
 #

drivers/gpu/drm/drm_client_setup.c

@@ -64,3 +64,6 @@ void drm_client_setup_with_color_mode(struct drm_device *dev, unsigned int color
 	drm_client_setup_with_fourcc(dev, fourcc);
 }
 EXPORT_SYMBOL(drm_client_setup_with_color_mode);
+
+MODULE_DESCRIPTION("In-kernel DRM clients");
+MODULE_LICENSE("GPL and additional rights");