SYSFS

The FBTFT drivers exposes some files in the sysfs filesystem.

Directory: /sys/class/graphics/fbX

FBTFT

Source code: https://github.com/notro/fbtft/blob/master/fbtft-sysfs.c

debug

Enable debug output to kernel log. More info

gamma

Supported by some drivers. Driver specific, see Gamma
Read:

000F 0000 0007 0002 0000 0000 0006 0005 0004 0001
0004 0016 0002 0007 0006 0003 0002 0001 0007 0007

Framebuffer subsystem

Source code: http://lxr.free-electrons.com/source/drivers/video/fbsysfs.c

bits_per_pixel

Read: fb_info->var.bits_per_pixel 16
Write: not supported by FBTFT

blank

Read: (can be read, but returns nothing)
Write: Currently only supported by ssd1351fb

# blank display
echo "4" | sudo tee blank

# unblank display
echo "0" | sudo tee blank

bl_curve

Only works with drivers that have registered a backlight device. Not used by FBTFT, as it doesn't support PWM.

console

(does nothing)

cursor

(does nothing)

mode

Read: If set: fb_info->mode
Write: does not apply to FBTFT

modes

Read: fb_info->modelist U:128x128p-0
Write: does not apply to FBTFT

name

Read: fb_info->fix.id (driver name) ssd1351fb

pan

Read: fb_info->var.xoffset, fb_info->var.yoffset 0,0
Write: not supported by FBTFT

rotate

Read: fb_info->var.rotate 0
Write: not supported by FBTFT

state

Read: fb_info->state 0
Write: Calls fb_set_suspend()

stride

Read: fb_info->fix.line_length 256

virtual_size

Read: fb_info->var.xres_virtual, fb_info->var.yres_virtual 128,128
Write: not supported by FBTFT

OTHER

dev

Read: 29:1

device -> ../../../spi0.0

power/

(empty directory)

subsystem -> ../../../../../../../../class/graphics

uevent

Read:

MAJOR=29
MINOR=1
DEVNAME=fb1

Write: don't know

Backlight

Many FBTFT drivers have backlight support

Directory: /sys/backlight/{driver}/

Source code: http://lxr.free-electrons.com/source/drivers/video/backlight/backlight.c
Ref: https://www.kernel.org/doc/Documentation/ABI/stable/sysfs-class-backlight

bl_power

Turn backlight on/off

# backlight off
echo "1" | sudo tee bl_power

# backlight on
echo "0" | sudo tee bl_power

type

Read: backlight_types[bd->props.type] raw

Brightness

Does not apply to FBTFT

• brightness
• actual_brightness
• max_brightness

Appendix

pi@raspberrypi /sys/class/graphics/fb1 $ ls -l
total 0
-rw-r--r-- 1 root root 4096 Jul  2 23:15 bits_per_pixel
-rw-r--r-- 1 root root 4096 Jul  2 23:15 blank
-rw-r--r-- 1 root root 4096 Jul  2 23:15 bl_curve
-rw-r--r-- 1 root root 4096 Jul  2 23:15 console
-rw-r--r-- 1 root root 4096 Jul  2 23:15 cursor
-r--r--r-- 1 root root 4096 Jul  2 23:15 dev
lrwxrwxrwx 1 root root    0 Jul  2 23:15 device -> ../../../spi0.0
-rw-rw-rw- 1 root root 4096 Jul  2 23:15 gamma
-rw-r--r-- 1 root root 4096 Jul  2 23:15 mode
-rw-r--r-- 1 root root 4096 Jul  2 23:15 modes
-r--r--r-- 1 root root 4096 Jul  2 23:15 name
-rw-r--r-- 1 root root 4096 Jul  2 23:15 pan
drwxr-xr-x 2 root root    0 Jul  2 23:15 power
-rw-r--r-- 1 root root 4096 Jul  2 23:15 rotate
-rw-r--r-- 1 root root 4096 Jul  2 23:15 state
-r--r--r-- 1 root root 4096 Jul  2 23:15 stride
lrwxrwxrwx 1 root root    0 Jul  2 23:15 subsystem -> ../../../../../../../../class/graphics
-rw-r--r-- 1 root root 4096 Jul  2 23:15 uevent
-rw-r--r-- 1 root root 4096 Jul  2 23:15 virtual_size