[PATCH v2 07/11] staging: mt7621-mmc: Check for nonzero number of scatterlist entries

[George Hilliard <thirtythreeforty@gmail.com>]

The buffer descriptor setup loop is correct only if it is setting up at
least one bd struct.  Besides, there is an error somewhere if
dma_map_sg() returns 0.  So add a paranoid check for this condition.

Signed-off-by: George Hilliard <thirtythreeforty@gmail.com>
---
 drivers/staging/mt7621-mmc/sd.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/mt7621-mmc/sd.c b/drivers/staging/mt7621-mmc/sd.c
index c272aa780719..31c5b44bd29f 100644
--- a/drivers/staging/mt7621-mmc/sd.c
+++ b/drivers/staging/mt7621-mmc/sd.c
@@ -593,7 +593,12 @@ 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 */
+	// Shouldn't happen; we configure the mmc host layer
+	// based on MAX_BD_NUM:
+	BUG_ON(sglen > MAX_BD_NUM);
+	// Correct setup below requires at least one bd
+	// (and dma_map_sg should not return 0):
+	BUG_ON(sglen == 0);
 
 	gpd = dma->gpd;
 	bd  = dma->bd;
-- 
2.21.0