2010/10/13 Björn Smedman <bjorn.smedman@xxxxxxxxxxx>:
> Hi Ben,
>
> First of all keep up the good work. :)
>
> On Wed, Oct 13, 2010 at 6:39 PM, Ben Greear <greearb@xxxxxxxxxxxxxxx> wrote:
> [snip]
>> Either way, it seems safer to null out the bf_ampdu field after
>> the memory is consumed..it could prevent some tricky bugs later.
>
> I think this is a good idea. But it probably wont be enough to null
> out bf_mpdu. You also need to look at bf_buf_addr (which if I
> understand correctly is the physical address the DMA engine will
> actually write RXed frames to) and bf_dmacontext (which seems in most
> cases to hold an identical address and may in fact be where the DMA
> engine will really write the frame).
I took another look at the code. It turns out both bf_buf_addr and
bf_dmacontext are in fact meaningless to the DMA. Instead each bf
holds a pointer (bf_desc) to the real DMA descriptor which in turn
holds the address (ds_data) where the DMA will really (really this
time) write the frame. There is also a field to hold the virtual
address of the same place (ds_vdata).
It's a little too much work for me to set up the testbed you have Ben
but would be interesting to see what happens if you set
bf->bf_desc->ds_{data,vdata} = 0 as well. No?
/Björn
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