My screen size is 1024x600. This is kernel source linux-fslc (branch 4.1-1.0.x-imx) on GitHub that I used. Below are my steps to enable splash screen in kernel:
1. Create an image (logo_custom_clut224.png) which resolution is 1024x600 then export it to ppm extension by using GIMP.
2. Add the line below to "include/linux/linux_logo.h"
extern const struct linux_logo logo_custom_clut224;
3. Add these line to "drivers/video/logo/logo.c"
#ifdef CONFIG_LOGO_CUSTOM_CLUT224
logo = &logo_custom_clut224;
#endif
4. Add a line to Makefile "drivers/video/logo/Makefile"
obj-$(CONFIG_LOGO_CUSTOM_CLUT224) += logo_custom_clut224.o
5. Add these line to Kconfig "drivers/video/logo/Kconfig"
config CONFIG_LOGO_CUSTOM_CLUT224
bool "Standard 224-color custom logo"
default n
6. Reconfiguring kernel using menuconfig.
CONFIG_LOGO_CUSTOM_CLUT224=y
7. Rebuild kernel. Built success.
Unfortunately, The splash screen didn't show. Can Anyone give some advice? Is there anything wrong with my picture?