Re: m68k: trying accessing fb memory

Dear Lambert,

well i finally managed to use smem_start to access memory, and for
screen refresh i have to some ioctl, since i need to refresh some square
areas for sprites dislpay.

Many Thanks
Best Regards

Angelo

On 13/12/2012 23:07, Gavin Lambert wrote:
> 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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