Re: [PATCH RFC v3 0/3] Add splash DRM client

[Francesco Valla <francesco@valla.it>]

Hello Mario,

Thank you for taking a stab at this.

On Mon, May 11, 2026 at 08:59:14PM -0500, Mario Limonciello wrote:
> 
> 
> On 5/10/26 16:29, Francesco Valla wrote:
> > Hello,
> > 
> > this is the third (and hopefully last) RFC version for the DRM-based
> > splash screen.
> > 
> > Motivation behind the work can be found in v1 [0]; in a nutshell, the
> > splash DRM client can draw a splashscreen using:
> > 
> >    - the BMP image supplied by the EFI BGRT;
> >    - a BMP image loaded as firmware (either built-in or loaded from the
> >      filesystem);
> >    - a colored background.
> > 
> > This revision greatly simplifies the image seletion logic; now the EFI
> > BGRT is always used as first source if enabled, with a fallback to BMP
> > image loaded as firmware and then to a plain color.
> > 
> > Sanity checks on the EFI BGRT image have been borrowed from the efifb
> > driver. More complete splash providers (e.g.: Plymouth) have an
> > extensive management of platform-specific quirks, but I don't think it
> > would be reasonable to introduce such complexity here.
> > 
> > Additional notes:
> >    - Rotation is still not managed (and probably won't?).
> >    - Support for tiled screens is untested.
> >    - Plain color and BMP sources were tested on QEMU, Beagleplay and
> >      i.MX93 FRDM.
> >    - EFI BGRT support was tested using QEMU+OVMF.
> > 
> > Thank you in advance for any feedback.
> 
> Unfortunately I found that I couldn't compile with my normal Kconfig.
> 
> ERROR: modpost: "bgrt_tab" [drivers/gpu/drm/clients/drm_client_lib.ko]
> undefined!
> ERROR: modpost: "bgrt_image_size"
> [drivers/gpu/drm/clients/drm_client_lib.ko] undefined!
> make[2]: *** [scripts/Makefile.modpost:147: Module.symvers] Error 1
> make[1]: *** [/home/supermario/src/linux/Makefile:2091: modpost] Error 2
> make: *** [Makefile:248: __sub-make] Error 2
> 
> ❮ grep ^CONFIG_DRM .config
> CONFIG_DRM=y
> CONFIG_DRM_KMS_HELPER=m
> CONFIG_DRM_DRAW=y
> CONFIG_DRM_CLIENT=y
> CONFIG_DRM_CLIENT_LIB=m

Here lies the source of the issue, since I forgot to export the BGRT
table symbols. In my test setup I had the clients built-in and didn't
catch this. A simple patch (which will be included in v4) is attached.

> CONFIG_DRM_CLIENT_SELECTION=m
> CONFIG_DRM_CLIENT_SETUP=y
> CONFIG_DRM_FBDEV_EMULATION=y
> CONFIG_DRM_FBDEV_OVERALLOC=100
> CONFIG_DRM_CLIENT_SPLASH=y
> CONFIG_DRM_CLIENT_SPLASH_BACKGROUND_COLOR=0x000000
> CONFIG_DRM_CLIENT_SPLASH_SRC_BGRT=y
> CONFIG_DRM_CLIENT_SPLASH_BMP_SUPPORT=y
> CONFIG_DRM_CLIENT_DEFAULT_SPLASH=y
> CONFIG_DRM_CLIENT_DEFAULT="splash"
> CONFIG_DRM_LOAD_EDID_FIRMWARE=y
> CONFIG_DRM_DISPLAY_HELPER=m
> CONFIG_DRM_DISPLAY_DP_AUX_CHARDEV=y
> CONFIG_DRM_DISPLAY_DP_HELPER=y
> CONFIG_DRM_DISPLAY_DSC_HELPER=y
> CONFIG_DRM_DISPLAY_HDCP_HELPER=y
> CONFIG_DRM_DISPLAY_HDMI_CEC_NOTIFIER_HELPER=y
> CONFIG_DRM_DISPLAY_HDMI_HELPER=y
> CONFIG_DRM_TTM=m
> CONFIG_DRM_EXEC=m
> CONFIG_DRM_BUDDY=m
> CONFIG_DRM_TTM_HELPER=m
> CONFIG_DRM_GEM_SHMEM_HELPER=m
> CONFIG_DRM_SUBALLOC_HELPER=m
> CONFIG_DRM_SCHED=m
> CONFIG_DRM_PANEL_BACKLIGHT_QUIRKS=m
> CONFIG_DRM_PRIVACY_SCREEN=y
> CONFIG_DRM_AMDGPU=m
> CONFIG_DRM_AMDGPU_CIK=y
> CONFIG_DRM_AMDGPU_USERPTR=y
> CONFIG_DRM_AMD_ISP=y
> CONFIG_DRM_AMD_ACP=y
> CONFIG_DRM_AMD_DC=y
> CONFIG_DRM_AMD_DC_FP=y
> CONFIG_DRM_AMD_SECURE_DISPLAY=y
> CONFIG_DRM_BRIDGE=y
> CONFIG_DRM_PANEL_BRIDGE=y
> CONFIG_DRM_PANEL=y
> CONFIG_DRM_SYSFB_HELPER=m
> CONFIG_DRM_SIMPLEDRM=m
> CONFIG_DRM_PANEL_ORIENTATION_QUIRKS=y
> CONFIG_DRM_ACCEL=y
> CONFIG_DRM_ACCEL_AMDXDNA=m
> CONFIG_DRM_ACCEL_HABANALABS=m
> CONFIG_DRM_ACCEL_IVPU=m
> CONFIG_DRM_ACCEL_QAIC=m
> ❮ grep BGRT .config
> CONFIG_ACPI_BGRT=y
> CONFIG_DRM_CLIENT_SPLASH_SRC_BGRT=y
>

Regards,
Francesco

---
 drivers/firmware/efi/efi-bgrt.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/firmware/efi/efi-bgrt.c b/drivers/firmware/efi/efi-bgrt.c
index 1da451582812..4ca06ed5d6f5 100644
--- a/drivers/firmware/efi/efi-bgrt.c
+++ b/drivers/firmware/efi/efi-bgrt.c
@@ -17,7 +17,10 @@
 #include <linux/efi-bgrt.h>
 
 struct acpi_table_bgrt bgrt_tab;
+EXPORT_SYMBOL(bgrt_tab);
+
 size_t bgrt_image_size;
+EXPORT_SYMBOL(bgrt_image_size);
 
 struct bmp_header {
        u16 id;
--