Lexra Pixnet

Safe Reboot Using Magic SysRq key

We can also do this by echoing the keys to the /proc/sysrq-trigger file. For example, to re-boot a system you can perform the following:  

# echo b > /proc/sysrq-trigger

List of SysRq Command Keys
 

Following are the command keys available for Alt+SysRq+commandkey.

‘k’ – Kills all the process running on the current virtual console.
‘s’ – This will attempt to sync all the mounted file system.
‘b’ – Immediately reboot the system, without unmounting partitions or syncing.
‘e’ – Sends SIGTERM to all process except init.
‘m’ – Output current memory information to the console.
‘i’ – Send the SIGKILL signal to all processes except init
‘r’ – Switch the keyboard from raw mode (the mode used by programs such as X11), to XLATE mode.
‘s’ – sync all mounted file system.
‘t’ – Output a list of current tasks and their information to the console.
‘u’ – Remount all mounted filesystems in readonly mode.
‘o’ – Shutdown the system immediately.
‘p’ – Print the current registers and flags to the console.
‘0-9′ – Sets the console log level, controlling which kernel messages will be printed to your console.
‘f’ – Will call oom_kill to kill process which takes more memory.
‘h’ – Used to display the help. But any other keys than the above listed will print help.

IMX6 Framebuffer Rotate Using SYSFS
 

# echo 0 > /sys/devices/platform/mxc_sdc_fb.0/graphics/fb0/rotate
# echo 0 > /sys/devices/platform/mxc_sdc_fb.0/graphics/fb1/rotate

# echo 1 > /sys/devices/platform/mxc_sdc_fb.0/graphics/fb0/rotate
# echo 1 > /sys/devices/platform/mxc_sdc_fb.0/graphics/fb1/rotate

Watchdog Enable (60 seconds) / Disable

# echo a > /dev/watchdog

# echo V > /dev/watchdog

Change the Android DPI (Dots Per Inch)

# vi /system/build.prop
...
ro.sf.lcd_density=240
ro.sf.lcd_density=160
ro.sf.lcd_density=120
...

PCM Device Node

Major and minor device node number on specific CARD_NO . 

DEVICE MAJOR_NO=116
DEVICE MINOR_NO=$((CARD_NO*32+16))

mknod /dev/snd/pcmC0D0p c 116 16
mknod /dev/snd/pcmC0D1p c 116 17
mknod /dev/snd/pcmC0D2p c 116 18
mknod /dev/snd/pcmC0D3p c 116 19
mknod /dev/snd/pcmC0D4p c 116 20
mknod /dev/snd/pcmC0D5p c 116 21
mknod /dev/snd/pcmC0D6p c 116 22
mknod /dev/snd/pcmC0D7p c 116 23
mknod /dev/snd/pcmC1D0p c 116 48
mknod /dev/snd/pcmC1D1p c 116 49
mknod /dev/snd/pcmC1D2p c 116 50
mknod /dev/snd/pcmC1D3p c 116 51
mknod /dev/snd/pcmC1D4p c 116 52
mknod /dev/snd/pcmC1D5p c 116 53
mknod /dev/snd/pcmC1D6p c 116 54
mknod /dev/snd/pcmC1D7p c 116 55
mknod /dev/snd/pcmC2D0p c 116 80
mknod /dev/snd/pcmC2D1p c 116 81
mknod /dev/snd/pcmC2D2p c 116 82
mknod /dev/snd/pcmC2D3p c 116 83
mknod /dev/snd/pcmC2D4p c 116 84
mknod /dev/snd/pcmC2D5p c 116 85
mknod /dev/snd/pcmC2D6p c 116 86
mknod /dev/snd/pcmC2D7p c 116 87
mknod /dev/snd/pcmC3D0p c 116 112
mknod /dev/snd/pcmC3D1p c 116 113
mknod /dev/snd/pcmC3D2p c 116 114
mknod /dev/snd/pcmC3D3p c 116 115
mknod /dev/snd/pcmC3D4p c 116 116
mknod /dev/snd/pcmC3D5p c 116 117
mknod /dev/snd/pcmC3D6p c 116 118
mknod /dev/snd/pcmC3D7p c 116 119
mknod /dev/snd/pcmC0D0c c 116 24
mknod /dev/snd/pcmC0D1c c 116 25
mknod /dev/snd/pcmC0D2c c 116 26
mknod /dev/snd/pcmC0D3c c 116 27
mknod /dev/snd/pcmC0D4c c 116 28
mknod /dev/snd/pcmC0D5c c 116 29
mknod /dev/snd/pcmC0D6c c 116 30
mknod /dev/snd/pcmC0D7c c 116 31
mknod /dev/snd/pcmC1D0c c 116 56
mknod /dev/snd/pcmC1D1c c 116 57
mknod /dev/snd/pcmC1D2c c 116 58
mknod /dev/snd/pcmC1D3c c 116 59
mknod /dev/snd/pcmC1D4c c 116 60
mknod /dev/snd/pcmC1D5c c 116 61
mknod /dev/snd/pcmC1D6c c 116 62
mknod /dev/snd/pcmC1D7c c 116 63
mknod /dev/snd/pcmC2D0c c 116 88
mknod /dev/snd/pcmC2D1c c 116 89
mknod /dev/snd/pcmC2D2c c 116 90
mknod /dev/snd/pcmC2D3c c 116 91
mknod /dev/snd/pcmC2D4c c 116 92
mknod /dev/snd/pcmC2D5c c 116 93
mknod /dev/snd/pcmC2D6c c 116 94
mknod /dev/snd/pcmC2D7c c 116 95
mknod /dev/snd/pcmC3D0c c 116 120
mknod /dev/snd/pcmC3D1c c 116 121
mknod /dev/snd/pcmC3D2c c 116 122
mknod /dev/snd/pcmC3D3c c 116 123
mknod /dev/snd/pcmC3D4c c 116 124
mknod /dev/snd/pcmC3D5c c 116 125
mknod /dev/snd/pcmC3D6c c 116 126
mknod /dev/snd/pcmC3D7c c 116 127