> -----Original Message-----
> From: Andrea Merello <andrea.merello@xxxxxxxxx>
> Sent: Friday, November 16, 2018 7:26 PM
> To: vkoul@xxxxxxxxxx; dan.j.williams@xxxxxxxxx; dmaengine@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx; Radhey Shyam Pandey
> <radheys@xxxxxxxxxx>; Andrea Merello <andrea.merello@xxxxxxxxx>
> Subject: [PATCH] dmaengine: fix dmaengine_desc_callback_valid() doesn't
> check for callback_result
>
> There are two flavors of DMA completion callbacks: callback() and
> callback_result(); the latter takes an additional parameter that carries
> result information.
>
> Most dmaengine helper functions that work with callbacks take care of both
> flavors i.e. dmaengine_desc_get_callback_invoke() first checks for
> callback_result() to be not NULL, and eventually it calls this one;
> otherwise it goes on checking for callback().
>
> It seems however that dmaengine_desc_callback_valid() does not care about
> callback_result(), and it returns false in case callback() is NULL but
> callback_result() is not; unless there is a (hidden to me) reason for doing
> so then I'd say this is wrong.
>
> I've hit this by using a DMA controller driver (xilinx_dma) that doesn't
> trigger any callback invocation unless dmaengine_desc_callback_valid()
> returns true, while I had only callback_result() implemented in my client
> driver (which AFAICT is always fine since dmaengine documentation says that
> callback() will be deprecated).
Thanks for the patch. In xilinx_dma driver call to _desc_callback_valid
can be safely removed as callback ptrs are anyway checked in invoke().
There is no much benefit in having redundant checks.
Related to dmaengine_desc_callback_valid extension will let Vinod comment.
>
> This patch fixes this by making dmaengine_desc_callback_valid() to return
> true in the said scenario.
>
> Signed-off-by: Andrea Merello <andrea.merello@xxxxxxxxx>
> ---
> drivers/dma/dmaengine.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/dma/dmaengine.h b/drivers/dma/dmaengine.h
> index 501c0b063f85..0ba2c1f3c55d 100644
> --- a/drivers/dma/dmaengine.h
> +++ b/drivers/dma/dmaengine.h
> @@ -168,7 +168,7 @@ dmaengine_desc_get_callback_invoke(struct
> dma_async_tx_descriptor *tx,
> static inline bool
> dmaengine_desc_callback_valid(struct dmaengine_desc_callback *cb)
> {
> - return (cb->callback) ? true : false;
> + return (cb->callback || cb->callback_result);
> }
>
> #endif
> --
> 2.17.1
