Re: [RFC 1/6] drm: Add top level Kconfig option for DRM fbdev emulation

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Mar 10, 2015 at 03:11:28PM +0530, Archit Taneja wrote:
> 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@codeaurora.org>
> ---
>  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

This should work as

drm_kms_helper-$CONFIG_DRM_FBDEV_EMULATION += drm_fb_helper.o

since both <modename>-y and <modename>-m are merged together.
-Daniel

> +
>  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
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> hosted by The Linux Foundation
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch