Re: Auto-detecting touchscreen controller and dealing with hw configuration differences on q8 tablets

[Holger Schurig <holgerschurig@gmail.com>]

> u-boot will work, but you will get into trouble if you demand users to drop to u-boot
> to make changes.

On my device I use barebox, which is a bit easier *) to use than U-Boot.

Still I don't expect my users to the bootloader. Instead my hardware has
a 256 byte i2c EEPROM where I store information. And the user can run a
user-space command to change settings there, e.g.

uccomm verbose_boot yes
uccomm power_config ignition

... and so on. I could do some of them via bootloader environment files,
but not all.

And this is the other obvious way of doing "communication" from Linux
user-space to bootloader: setting the environment. The bootloader could
mount the partition and try to source some file, to get the info needed.




*) in barebox, you have actual shell-like script that look sane, not
 variables that call variables, e.g. you can do things like this:

	if [ $oem_id = 255 ]; then
		splash -x 550 -y 500 -b 0xffffff /env/logo.png
		fb0.enable=1
		pwm_02080000.period_ns=200000
		pwm_02080000.duty_ns=160000
		pwm_02080000.enable=1
	fi
	gpio_set_value 191 1

There are also commands available to directly modify the device tree.