linux-kernel - [PATCH] dmaengine: fix dmaengine_desc_callback_valid() doesn't check for callback

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Date:   Fri, 16 Nov 2018 14:56:28 +0100
From:   Andrea Merello <andrea.merello@...il.com>
To:     vkoul@...nel.org, dan.j.williams@...el.com,
        dmaengine@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, radhey.shyam.pandey@...inx.com,
        Andrea Merello <andrea.merello@...il.com>
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 <andrea.merello@...il.com>
---
 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