Re: [Linux-fbdev-devel] DMA/IRQ based hardware support.

[Scott A M. <sam...@co...>]

James Simmons wrote:
> 
> The ruby tree has finished the moved away from using spinlocks to a
> sempahore for the console lock.

Has this issue been discussed on this list?

The sempahore gives better support for threads/tasks?


> This means we can now have fbdev drivers
> that use DMA :-) We can now write fbdev drivers using DMA. Thank you.

Please pardon my ignorance...

When/why would you want to use DMA? Do all the drawing on CPU memory and
then DMA
the block to graphics memory? It seems that approach would get in the
way of acceleration.

Using DMA inside the acceleration routines? It seems on average you
would spend more time making the tests to decide to use DMA and
programming the DMA then it would be to write the pixels directly.

It seems most operations on fb would involve "small" rectangles that do
not use large contigous blocks of memory. Console scrolling would be
able to take advantage of it...

Thanks for any comments.


-- 
Scott A. McConnell