On 04/12/2016 10:01 AM, Mark Brown wrote:
> On Tue, Apr 05, 2016 at 09:19:51AM +0530, Vignesh R wrote:
>
>> mutex_lock(&master->bus_lock_mutex);
>> + if (master->dma_rx) {
>> + rx_dev = master->dma_rx->device->dev;
>> + ret = spi_map_buf(master, rx_dev, &msg->rx_sg,
>> + msg->buf, msg->len,
>> + DMA_FROM_DEVICE);
>> + if (ret != 0)
>> + goto err;
>> + }
>
> This is unconditionally DMA mapping the buffer if DMA is supported.
> That's going to be common but I'm not sure it'll be universal, we need
> to think of something better here. I'm not immediately seeing what
> though. Possibly a flag...
>
Ok, I will introduced a flag along the lines of cur_msg_mapped currently
part of spi_message struct.
This reminds me the issue of possible kmap'd buffers(falling in
PKMAP_BASE - PAGE_OFFSET-1 region) that might be passed to
spi_map_buf() which are not currently being handled properly. Boris
attempted to fix this in generic way[1] but was rejected as it couldn't
handle all type of caches.
I was wondering whether you would accept a patch returning error when
kmap'd buffers are passed to spi_map_buf()? Or would it still make sense
to port changes from that series to handle kmap'd buffers to SPI core alone?
[1]https://lkml.org/lkml/2016/3/31/462
--
Regards
Vignesh
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