On Tue, Feb 07, 2017 at 02:32:15PM +0530, Anup Patel wrote:

On Tue, Feb 7, 2017 at 1:57 PM, Dan Williams [off-list ref] wrote:

quoted

On Tue, Feb 7, 2017 at 12:16 AM, Anup Patel [off-list ref] wrote:

quoted

The DMAENGINE framework assumes that if PQ offload is supported by a
DMA device then all 256 PQ coefficients are supported. This assumption
does not hold anymore because we now have BCM-SBA-RAID offload engine
which supports PQ offload with limited number of PQ coefficients.

This patch extends async_tx APIs to handle DMA devices with support
for fewer PQ coefficients.

Signed-off-by: Anup Patel <redacted>
Reviewed-by: Scott Branden <scott.branden@broadcom.com>

I don't like this approach. Define an interface for md to query the
offload engine once at the beginning of time. We should not be adding
any new extensions to async_tx.

Even if we do capability checks in Linux MD, we still need a way
for DMAENGINE drivers to advertise number of PQ coefficients
handled by the HW.

If the question is only for advertising caps, then why not do as done
for dma_get_slave_caps(). you can add dma_get_pq_caps() so that clients (md)
in this case would know the HW capability.

I agree capability checks should be done once in Linux MD but I don't
see why this has to be part of BCM-SBA-RAID driver patches. We need
separate patchsets to address limitations of async_tx framework.

Regards,
Anup

-- 
~Vinod