linux-kernel - [PATCH v3 3/3] staging: mt7621-mmc: Check for nonzero number of scatterlist entries

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Message-Id: <20190320224204.10243-4-thirtythreeforty@gmail.com>
Date:   Wed, 20 Mar 2019 16:42:05 -0600
From:   George Hilliard <thirtythreeforty@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-mips@...ux-mips.org, linux-kernel@...r.kernel.org,
        George Hilliard <thirtythreeforty@...il.com>
Subject: [PATCH v3 3/3] staging: mt7621-mmc: Check for nonzero number of scatterlist entries

The buffer descriptor setup loop is correct only if it is setting up at
least one bd struct.  Besides, there is an error if dma_map_sg() returns
0, which is possible and must be handled.

Additionally, remove the BUG_ON() checking sglen, which is unnecessary
because we configure DMA with that constraint during init.

Signed-off-by: George Hilliard <thirtythreeforty@...il.com>
---
v2: Rebased v1
v3: Remove existing and added BUG_ON() in v2, and handle dma_map_sg
    failure gracefully.

 drivers/staging/mt7621-mmc/sd.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/mt7621-mmc/sd.c b/drivers/staging/mt7621-mmc/sd.c
index 139533606863..cf2ad06112eb 100644
--- a/drivers/staging/mt7621-mmc/sd.c
+++ b/drivers/staging/mt7621-mmc/sd.c
@@ -593,8 +593,6 @@ static void msdc_dma_setup(struct msdc_host *host, struct msdc_dma *dma,
 	struct bd *bd;
 	u32 j;
 
-	BUG_ON(sglen > MAX_BD_NUM); /* not support currently */
-
 	gpd = dma->gpd;
 	bd  = dma->bd;
 
@@ -687,6 +685,13 @@ static int msdc_do_request(struct mmc_host *mmc, struct mmc_request *mrq)
 		data->sg_count = dma_map_sg(mmc_dev(mmc), data->sg,
 					    data->sg_len,
 					    mmc_get_dma_dir(data));
+
+		if (data->sg_count == 0) {
+			dev_err(mmc_dev(host->mmc), "failed to map DMA for transfer\n");
+			data->error = -ENOMEM;
+			goto done;
+		}
+
 		msdc_dma_setup(host, &host->dma, data->sg,
 			       data->sg_count);
 
-- 
2.21.0