MSI(-X) interface RFC (was: MSI prototype)

[Chuck Tuffli]

On 2/26/06, Matthew Dillon <dillon at xxxxxxxxxxxxxxxxxxxx> wrote:
[re: extra args to bus_setup_intr()]
. ..
>     Hmm.  I think that might be a bit too messy, not so much because of
>     the extra arguments, but because the arguments aren't really all that
>     generic and only apply to MSI(X) vectors.
>
>     I have an idea.
>
>     Have bus_alloc_resource() allocate the container that represents all
>     the vectors, just as you describe, but then create a
>     bus_alloc_sub_resource() procedure to separately allocate each vector
>     within that container.   Then call bus_setup_intr() for each vector
>     individually.  The driver needs to have a loop of some sort anyway
>     and this way we would actually have a resource descriptor for
>     each individual vector and we wouldn't have to hack up bus_setup_intr().

I like this idea alot! There still needs to be a way for
bus_setup_intr to know which MSI-X table entry to fill with the vector
info gleaned from bus_alloc_sub_resource(). Two thoughts come to mind:

1) encode the table entry in bus_setup_intr()'s flag parameter similar
to how aligment restrictions get passed into bus_alloc_resource with
rman_make_alignment_flags()

2) define a bus function that assigns a table entry number to the
resource. This would only be used for MSI-X as IRQ and MSI only have a
single entry for their interrupt info. I think this would be similar
in nature to BUS_CONFIG_INTR(9).

---chuck