Cc: David Brownell <david-b@...>, <linux-kernel@...>, Shannon Nelson <shannon.nelson@...>, <kernel@...>, Francis Moreau <francis.moro@...>, Paul Mundt <lethal@...>, Vladimir A. Barinov <vbarinov@...>, Pierre Ossman <drzeus-list@...>
On Wed, 30 Jan 2008 10:39:47 -0700
"Dan Williams" <dan.j.williams@intel.com> wrote:
I have to say I'm not crazy about the idea of adding more callbacks to
the descriptor...
The client must somehow know when the transfer is complete -- after
all, it has to call async_tx_ack() at some point. So additional
callbacks shouldn't be needed.
How about adding more variants of the "ack" function -- one for each
kind of transfer? For example, after an async_memcpy() transaction is
complete, the client must call async_memcpy_ack(), which could be an
inline function containing something along the lines of
static inline void async_memcpy_ack(struct dma_async_tx_descriptor *tx)
{
struct dma_device *dma = tx->chan->device;
dma_unmap_page(dma->dev, tx->src_phys, tx->len, DMA_TO_DEVICE);
dma_unmap_page(dma->dev, tx->dst_phys, tx->len, DMA_FROM_DEVICE);
async_tx_ack(tx);
}
which would evaluate to just async_tx_ack(tx) in most cases, since
dma_unmap_page() usually doesn't actually do anything.
This requires three additional fields in the dma_async_tx_descriptor
structure, but in many cases the driver needs these fields in its own
private descriptor wrapper anyway.
Haavard
--
