linux-kernel - [PATCH] dmaengine: at_xdmac: check for non-empty xfers

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Message-Id: <1561796448-3321-1-git-send-email-raagjadav@gmail.com>
Date:   Sat, 29 Jun 2019 13:50:48 +0530
From:   Raag Jadav <raagjadav@...il.com>
To:     dmaengine@...r.kernel.org, Vinod Koul <vkoul@...nel.org>
Cc:     Ludovic Desroches <ludovic.desroches@...rochip.com>,
        Dan Williams <dan.j.williams@...el.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Raag Jadav <raagjadav@...il.com>
Subject: [PATCH] dmaengine: at_xdmac: check for non-empty xfers_list before invoking callback

tx descriptor retrieved from an empty xfers_list may not have valid
pointers to the callback functions.
Avoid calling dmaengine_desc_get_callback_invoke if xfers_list is empty.

Signed-off-by: Raag Jadav <raagjadav@...il.com>
---
 drivers/dma/at_xdmac.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/dma/at_xdmac.c b/drivers/dma/at_xdmac.c
index 627ef3e..b58ac72 100644
--- a/drivers/dma/at_xdmac.c
+++ b/drivers/dma/at_xdmac.c
@@ -1568,11 +1568,14 @@ static void at_xdmac_handle_cyclic(struct at_xdmac_chan *atchan)
 	struct at_xdmac_desc		*desc;
 	struct dma_async_tx_descriptor	*txd;
 
-	desc = list_first_entry(&atchan->xfers_list, struct at_xdmac_desc, xfer_node);
-	txd = &desc->tx_dma_desc;
+	if (!list_empty(&atchan->xfers_list)) {
+		desc = list_first_entry(&atchan->xfers_list,
+					struct at_xdmac_desc, xfer_node);
+		txd = &desc->tx_dma_desc;
 
-	if (txd->flags & DMA_PREP_INTERRUPT)
-		dmaengine_desc_get_callback_invoke(txd, NULL);
+		if (txd->flags & DMA_PREP_INTERRUPT)
+			dmaengine_desc_get_callback_invoke(txd, NULL);
+	}
 }
 
 static void at_xdmac_handle_error(struct at_xdmac_chan *atchan)
-- 
2.7.4