EXA pixmap alignments.

Thomas Hellstrom unichrome at shipmail.org
Mon Sep 26 12:48:50 PDT 2005

Eric Anholt wrote:

>On Mon, 2005-09-26 at 09:55 +0200, Thomas Hellstrom wrote:
>>EXADriverPtr->card.pixmapOffsetAlign = ?
>>EXADriverPtr->card.pixmapPitchAlign = ?
>>Is there a chance to have the above parameters defined also for system 
>>to frame-buffer transfers?
>>For example Unichrome / Unichrome Pro currently requires both to be 16 
>>for PCI DMA to work, and as briefly discussed on the dri-devel list, 
>>system / frame-buffer bounce buffers to fix alignments may be very 
>I'm not quite clear on what you're asking about -- you said something
>about dst_addr%4 == src_addr%4.  EXA doesn't have anything to help you
>with that -- it can only ensure that the offset in card space is aligned
>to a multiple of some number, and/or the pitch of the pixmap is aligned
>to some number.  However, simply having the on-card offset aligned to 16
>and then doing a fixup on the system memory buffer (if necessary, which
>it usually wouldn't be, I bet) after copying out seems reasonable to me.
I'm not sure how EXA uses system memory buffers, but if they are used as 
temporary storage, then it would be desirable to be able to prescribe 
pitch and padding  alignments.

However, if they always are set up by other parts of the X server or shm 
clients it is clear that they cannot take alignment constraints into 


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