On Nov 16, 2008, at 5:08 AM, Hans Petter Selasky wrote:
Hi,
It turns out my initial patch need to be limited to the use-case
only. Before
I start any real work, I want to know if anyone will object if I
implement
the following new BUS_DMA flag into FreeBSD's busdma system?
amd64/amd64/busdma_machdep.c
i386/i386/busdma_machdep.c
arm/arm/busdma_machdep.c
ia64/ia64/busdma_machdep.c
mips/mips/busdma_machdep.c
powerpc/powerpc/busdma_machdep.c
sparc64/sparc64/bus_machdep.c
sun4v/sun4v/bus_machdep.c
sys/bus_dma.h
/*
* The following flag specifies that no re-alignment of individual
* memory pages is allowed when loaded into DMA. It can only be used
* when "maxsegsz" is equal to "PAGE_SIZE" and "alignment" is less
* than or equal to 1.
*
* Background: Some kinds of DMA hardware only stores the full
* physical address of the first memory page when multiple memory
* pages are loaded into DMA. Consequtive memory pages only gets the
* non-offset part of the physical address updated. The hardware
* computes the amount of data that should be stored in the first
* memory page from the minimum of the total transfer length and
* PAGE_SIZE minus the initial page offset. When the initial page
* offset is not preserved the hardware ends up transferring an
* invalid number of bytes to or from the initial memory page.
*/
#define BUS_DMA_NOREAL 0x400 /* no page re-alignment allowed */
No objection, but please call it
BUS_DMA_NOREALIGN
NOREAL reads as NO-REAL and not as NO-RE-AL. And with
real addressing an existing concept, confusion is not
far around the corner...
--
Marcel Moolenaar
[EMAIL PROTECTED]
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