I think it'd be very good to have a console_blank_hook handler that would call a userspace program/script/generate hotplug event whatever. Currently, the console can only be blanked using APM, so no options exist for people using ACPI. I've got a Radeon graphics chip on my laptop, and the LCD backlight can be controlled (on/off) using radeontool. If there was a userspace callback interface to console blanking, I would just make a callback script that calls "radeontool light off" on blank and "radeontool light on" on unblank - really easy. I think this userspace console_blank_hook handler is very simple to put into kernel, but I'm not a kernel developer myself, so wouldn't risk sending any patches (that call system("some_script")), because I probably won't make things as they should be in the kernel.
Created attachment 5238 [details] implemented this functionality in a kernel module I've actually checked the kernel sources on how this can be done and implemented the proposed functionality in a kernel module. The module attaches a console blank hook function that uses kernel's call_usermodehelper() to execute /sbin/user_vc_blank (defined at compile-time) to blank/unblank the console. I've written a sample script (which I use on my laptop) that uses radeontool to turn the LCD backlight off/on. Maybe this functionality should be moved to the kernel. On the other hand, as it still needs userspace utilities, maybe it's better off as a module. Anyway, please give it a thought, or at least made this module available.
Present this to lkml and linux-fbdev-devel list, if you want this functionality.