dmaengine: fix dmaengine_desc_callback_valid() doesn't check for callback_result

-----Original Message-----
From: Andrea Merello <[email protected]>
Sent: Friday, November 16, 2018 7:26 PM
To: [email protected]; [email protected]; [email protected]
Cc: [email protected]; Radhey Shyam Pandey <[email protected]>; Andrea Merello <[email protected]>
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).

This patch fixes this by making dmaengine_desc_callback_valid() to return true in the said scenario.

Signed-off-by Andrea Merello <[email protected]>

---
 drivers/dma/dmaengine.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

drivers/dma/dmaengine.h +1 -1

index 501c0b063f85..0ba2c1f3c55d 100644
@@ -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

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).

This patch fixes this by making dmaengine_desc_callback_valid() to return true in the said scenario.

Signed-off-by Andrea Merello <[email protected]>

---
 drivers/dma/dmaengine.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

drivers/dma/dmaengine.h +0 -0

index 501c0b063f85..0ba2c1f3c55d 100644