On Thu, Aug 11, 2011 at 4:27 PM, Paolo Bonzini <pbonz...@redhat.com> wrote: > On 08/11/2011 05:12 PM, Kevin Wolf wrote: >>> >>> > Another possibility is always completing DMA in a bottom half. This >>> > ensures that the callback can access the AIOCB, but it exposes an >>> > implementation detail to the caller, so I don't like it. >> >> At least in the block layer, AIO callbacks may never be called before >> the submission function has returned. I think this makes the DMA helpers >> provide the same behaviour. >> >> But I'm not sure if the definition of the AIOCB struct isn't private to >> the block layer. > > Yes, it is; I would add a getter that is specific to the DMAAIOCB.
You don't need to make the dma_bdrv_io() cb function a BlockDriverCompletionFunc. Instead define a DMACompletionFunc: typedef void DMACompletionFunc(void *opaque, int ret, target_phys_addr_t residual); The only one invoking dbs->common.cb is dma-helpers.c so you can just avoid using common.cb and instead use a DMACompletionFunc cb. Perhaps the AIOCB concept can be made generic where BlockDriverAIOCB inherits from it. I'm not even so sure that keeping a BlockDriverState pointer around is that useful. At least dma-helpers.c seems to think it's too much typing and it just duplicates the bs field into DMAAIOCB directly :). The question then becomes how to abstract the typed callback function nicely. Stefan
