Debug - notro/fbtft GitHub Wiki
FBTFT has dynamic debug support. This is enabled when loading the device or through sysfs when the driver is loaded.
sudo modprobe fbtft_device name=itdb28 debug=1
echo "5" > /sys/class/graphics/fb1/debug
Debug output can be turned on for individual functions setting bits. There is 7 shorthand debug levels 1-7.
The debug ouput goes to the kernel log. Can be viewed with dmesg
Here is the macros from fbtft.h
/* shorthand debug levels */
#define DEBUG_LEVEL_1 DEBUG_REQUEST_GPIOS
#define DEBUG_LEVEL_2 (DEBUG_LEVEL_1 | DEBUG_DRIVER_INIT_FUNCTIONS | DEBUG_TIME_FIRST_UPDATE)
#define DEBUG_LEVEL_3 (DEBUG_LEVEL_2 | DEBUG_RESET | DEBUG_INIT_DISPLAY | DEBUG_BLANK | DEBUG_REQUEST_GPIOS | DEBUG_FREE_GPIOS | DEBUG_VERIFY_GPIOS | DEBUG_BACKLIGHT | DEBUG_SYSFS)
#define DEBUG_LEVEL_4 (DEBUG_LEVEL_2 | DEBUG_FB_READ | DEBUG_FB_WRITE | DEBUG_FB_FILLRECT | DEBUG_FB_COPYAREA | DEBUG_FB_IMAGEBLIT | DEBUG_FB_BLANK)
#define DEBUG_LEVEL_5 (DEBUG_LEVEL_3 | DEBUG_UPDATE_DISPLAY)
#define DEBUG_LEVEL_6 (DEBUG_LEVEL_4 | DEBUG_LEVEL_5)
#define DEBUG_LEVEL_7 0xFFFFFFFF
#define DEBUG_DRIVER_INIT_FUNCTIONS (1<<3)
#define DEBUG_TIME_FIRST_UPDATE (1<<4)
#define DEBUG_TIME_EACH_UPDATE (1<<5)
#define DEBUG_DEFERRED_IO (1<<6)
#define DEBUG_FBTFT_INIT_FUNCTIONS (1<<7)
/* fbops */
#define DEBUG_FB_READ (1<<8)
#define DEBUG_FB_WRITE (1<<9)
#define DEBUG_FB_FILLRECT (1<<10)
#define DEBUG_FB_COPYAREA (1<<11)
#define DEBUG_FB_IMAGEBLIT (1<<12)
#define DEBUG_FB_SETCOLREG (1<<13)
#define DEBUG_FB_BLANK (1<<14)
#define DEBUG_SYSFS (1<<16)
/* fbtftops */
#define DEBUG_BACKLIGHT (1<<17)
#define DEBUG_READ (1<<18)
#define DEBUG_WRITE (1<<19)
#define DEBUG_WRITE_VMEM (1<<20)
#define DEBUG_WRITE_REGISTER (1<<21)
#define DEBUG_SET_ADDR_WIN (1<<22)
#define DEBUG_RESET (1<<23)
#define DEBUG_MKDIRTY (1<<24)
#define DEBUG_UPDATE_DISPLAY (1<<25)
#define DEBUG_INIT_DISPLAY (1<<26)
#define DEBUG_BLANK (1<<27)
#define DEBUG_REQUEST_GPIOS (1<<28)
#define DEBUG_FREE_GPIOS (1<<29)
#define DEBUG_REQUEST_GPIOS_MATCH (1<<30)
#define DEBUG_VERIFY_GPIOS (1<<31)
With Bash shell it's easy to set the individual bits:
# DEBUG_LEVEL_1, DEBUG_FB_BLANK, DEBUG_BLANK
sudo modprobe fbtft_device name=itdb28 debug=$((1 | 1<<14 | 1<<27))
# DEBUG_FB_SETCOLREG
echo $((1<<13)) > /sys/class/graphics/fb1/debug
If the driver is compiled into the kernel, the debug argument is set on the kernel command line
Add to /boot/cmdline.txt
fbtft.debug=1