Legacy fbdev emulation support via DRM is achieved through KMS FB helpers.
Most modesetting drivers enable provide fbdev emulation by default by selecting
KMS FB helpers. A few provide a separate Kconfig option for the user to enable
or disbale fbdev emulation.
Enabling fbdev emulation is finally a distro-level decision. Having a top level
Kconfig option for fbdev emulation helps by providing a uniform way to
enable/disable fbdev emulation for any modesetting driver. It also lets us
remove unnecessary driver specific Kconfig options that causes bloat.
With a top level Kconfig in place, we can stub out the fb helper functions when
not needed without breaking functionality. Having stub functions also prevents
drivers to require wrapping fb helper function calls with #ifdefs.
DRM_FBDEV_EMULATION defaults to y since many drivers enable fbdev emulation by
default and majority of distributions expect the fbdev interface in the kernel.
For now, this config selects both FB_SYS_* and FB_CFB_* configs as some
modesetting drivers use the former and other the later. This needs to be taken
care of in a better way.
Signed-off-by: Archit Taneja <architt@xxxxxxxxxxxxxx>
---
drivers/gpu/drm/Kconfig | 18 +++++++
drivers/gpu/drm/Makefile | 4 ++
include/drm/drm_fb_helper.h | 120 ++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 142 insertions(+)
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 151a050..38f83a0 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -40,6 +40,24 @@ config DRM_KMS_FB_HELPER
help
FBDEV helpers for KMS drivers.
+config DRM_FBDEV_EMULATION
+ bool "Enable legacy fbdev support for your modesetting driver"
+ depends on DRM
+ select DRM_KMS_HELPER
+ select DRM_KMS_FB_HELPER
+ select FB_SYS_FILLRECT
+ select FB_SYS_COPYAREA
+ select FB_SYS_IMAGEBLIT
+ select FB_SYS_FOPS
+ select FB_CFB_FILLRECT
+ select FB_CFB_COPYAREA
+ select FB_CFB_IMAGEBLIT
+ default y
+ help
+ Choose this option if you have a need for the legacy fbdev
+ support. Note that this support also provide the linux console
+ support on top of your modesetting driver.
+
config DRM_LOAD_EDID_FIRMWARE
bool "Allow to specify an EDID data set instead of probing for it"
depends on DRM_KMS_HELPER
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index 2c239b9..c1d44b2 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -25,7 +25,11 @@ drm-$(CONFIG_OF) += drm_of.o
drm_kms_helper-y := drm_crtc_helper.o drm_dp_helper.o drm_probe_helper.o \
drm_plane_helper.o drm_dp_mst_topology.o drm_atomic_helper.o
drm_kms_helper-$(CONFIG_DRM_LOAD_EDID_FIRMWARE) += drm_edid_load.o
+
+ifeq ($(CONFIG_DRM_FBDEV_EMULATION),y)
drm_kms_helper-$(CONFIG_DRM_KMS_FB_HELPER) += drm_fb_helper.o
+endif
+
drm_kms_helper-$(CONFIG_DRM_KMS_CMA_HELPER) += drm_fb_cma_helper.o
obj-$(CONFIG_DRM_KMS_HELPER) += drm_kms_helper.o
diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h
index 21b944c..dbfce1a 100644
--- a/include/drm/drm_fb_helper.h
+++ b/include/drm/drm_fb_helper.h
@@ -103,6 +103,7 @@ struct drm_fb_helper {
bool delayed_hotplug;
};
+#ifdef CONFIG_DRM_FBDEV_EMULATION
void drm_fb_helper_prepare(struct drm_device *dev, struct drm_fb_helper *helper,
const struct drm_fb_helper_funcs *funcs);
int drm_fb_helper_init(struct drm_device *dev,
@@ -139,4 +140,123 @@ drm_pick_cmdline_mode(struct drm_fb_helper_connector *fb_helper_conn,
int drm_fb_helper_add_one_connector(struct drm_fb_helper *fb_helper, struct drm_connector *connector);
int drm_fb_helper_remove_one_connector(struct drm_fb_helper *fb_helper,
struct drm_connector *connector);
+#else
+static inline void drm_fb_helper_prepare(struct drm_device *dev,
+ struct drm_fb_helper *helper,
+ const struct drm_fb_helper_funcs *funcs)
+{
+}
+
+static inline int drm_fb_helper_init(struct drm_device *dev,
+ struct drm_fb_helper *helper, int crtc_count,
+ int max_conn)
+{
+ return 0;
+}
+
+static inline void drm_fb_helper_fini(struct drm_fb_helper *helper)
+{
+}
+
+static inline int drm_fb_helper_blank(int blank, struct fb_info *info)
+{
+ return 0;
+}
+
+static inline int drm_fb_helper_pan_display(struct fb_var_screeninfo *var,
+ struct fb_info *info)
+{
+ return 0;
+}
+
+static inline int drm_fb_helper_set_par(struct fb_info *info)
+{
+ return 0;
+}
+
+static inline int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
+ struct fb_info *info)
+{
+ return 0;
+}
+
+static inline bool
+drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper)
+{
+ return true;
+}
+
+static inline void drm_fb_helper_fill_var(struct fb_info *info,
+ struct drm_fb_helper *fb_helper,
+ uint32_t fb_width, uint32_t fb_height)
+{
+}
+
+static inline void drm_fb_helper_fill_fix(struct fb_info *info, uint32_t pitch,
+ uint32_t depth)
+{
+}
+
+static inline int drm_fb_helper_setcmap(struct fb_cmap *cmap,
+ struct fb_info *info)
+{
+ return 0;
+}
+
+static inline int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper)
+{
+ return 0;
+}
+
+static inline int drm_fb_helper_initial_config(struct drm_fb_helper *fb_helper,
+ int bpp_sel)
+{
+ return 0;
+}
+
+static inline int
+drm_fb_helper_single_add_all_connectors(struct drm_fb_helper *fb_helper)
+{
+ return 0;
+}
+
+static inline int drm_fb_helper_debug_enter(struct fb_info *info)
+{
+ return 0;
+}
+
+static inline int drm_fb_helper_debug_leave(struct fb_info *info)
+{
+ return 0;
+}
+
+static inline struct drm_display_mode *
+drm_has_preferred_mode(struct drm_fb_helper_connector *fb_connector,
+ int width, int height)
+{
+ return NULL;
+}
+
+static inline struct drm_display_mode *
+drm_pick_cmdline_mode(struct drm_fb_helper_connector *fb_helper_conn,
+ int width, int height)
+{
+ return NULL;
+}
+
+static inline int
+drm_fb_helper_add_one_connector(struct drm_fb_helper *fb_helper,
+ struct drm_connector *connector)
+{
+ return 0;
+}
+
+static inline int
+drm_fb_helper_remove_one_connector(struct drm_fb_helper *fb_helper,
+ struct drm_connector *connector)
+{
+ return 0;
+}
+#endif
+
#endif
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