Re: bus_get_dma_tag now necessary for drivers using bus_dma

On Tuesday 05 September 2006 20:31, Scott Long wrote:
Poul-Henning Kamp wrote:
In message <20060905173334.GH9421@xxxxxxxxxxxx>, John-Mark Gurney writes:
This means that for each call to bus_dma_tag_create, instead of passing
a NULL pointer, you should call bus_get_dma_tag(yourdev) and use that
as the parent tag. I committed some example code to various drivers,
such as ahc, ata, em, and ohci.

If there are never any exeptions to this requirement, why not
pass "yourdev" and have the magic hidden, rather than add 17
ritual characters to the API ?

Drivers can have their own multi-level tag heirarchy. You'd have to
create a new bus_dma_tag_create() variant that expected a device_t
instead of a bus_dma_tag_t. This might be a good idea.


I think it is easier to share code with NetBSD if we use
"bus_get_dma_tag(yourdev)".

For example I use the following prototype on NetBSD and FreeBSD:

void *
usbd_mem_alloc(bus_dma_tag_t parent, u_int32_t size,
u_int8_t align_power);

--HPS
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