Kernel arguments

Kernel arguments can be specified in bootargs U-boot environment variable or can be compiled into kernel.

The U-boot variables can be compiled in as default environment, saved in the environment on media or specified in boot.scr

An example of kernel command line arguments:

console=ttyS0,115200 hdmi.audio=EDID:0 disp.screen0_output_mode=EDID:1280x1024p60 root=/dev/mmcblk0p1 rootwait panic=10


 * console=ttyS0,115200 is for taking over the serial port after u-boot. These are the default settings u-boot uses. You can specify console=ttyS0,115200 console=tty0 for both serial and framebuffer console


 * hdmi.audio=EDID:0 this should presumably turn on HDMI audio only when screen EDID says it supports audio. Omit EDID to just turn on - 1 or off - 0. Currently HDMI audio is enabled even on screen that definitly does not support it - YMMW.


 * disp.screen0_output_mode=EDID:1280x1024p60 screen 0 is the first screen configured in script.bin. EDID instructs the kernel to try to read mode from the screen. Failing that you can pick a mode from a fixed mode list in the driver. Again, omit EDID to override mode manually. You can try to figure out supported modes from files like https://github.com/linux-sunxi/linux-sunxi/blob/sunxi-3.0/drivers/video/sunxi/disp/disp_clk.c


 * root=/dev/mmcblk0p1 - root on first mmc device first partition. Use /dev/nandc for nand third partition (new partitioning scheme uses /dev/nand3) Some images use label or UUID to identify the root filesystem. /dev/sda1 identifies first SCSI device first partition but as both internal SATA and USB mass storage use SCSI emulation this device name is not assigned deterministically. Use labels or UUIDs for SCSI devices.


 * rootwait - this was in the default environment. Not sure what would break if omitted.


 * panic=10 - the amount of time in seconds to wait before rebooting after kernel panic.

Feel free to add other relevant arguments. This list is not exhaustive.