Re: m68k: trying accessing fb memory

Quoth angelo:
> Seems that for my case (m68k-nommu) it is not defined, so none of the 
> get_unmapped_area will be called, in any place.

It doesn't need to be defined.  fbmem.c implements get_unmapped_area
regardless (just slightly differently in each case).  If you had actually
tried just setting smem_start as I said you should have seen it working.

> thanks, i tried your solution, works, i am able to write on the lcd
> video memory using mmap() on /dev/mem, but there is still the issue of
> refreshing the lcd i am driving.

Without an MMU, there is no way to get a callback when an application writes
directly to framebuffer memory.  If your device requires you to take some
action beyond just updating the memory (eg. sending some kind of extra
command) then you will either need to use an ioctl to request a screen
refresh each time the app finishes drawing (which only works if you are in
control of the app's code) or to use some other mechanism to detect when the
framebuffer memory has been changed.

Another LCD driver I have creates a shadow copy of the framebuffer and has a
worker thread periodically compare the main framebuffer and the shadow
buffer; whenever it finds a difference it copies it to the shadow buffer and
updates the LCD.  It's a bit crude, and it limits the frame rate to whatever
rate the worker thread runs at, but it works.


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