[PATCH 1/3] i2c: rcar: sanity check for minimal DMA length

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Use a macro for the hardcoded value and apply a build check. If it is
not met, the driver logic will not work anymore.

Signed-off-by: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
---
 drivers/i2c/busses/i2c-rcar.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
index 3ce74edcd70c..925858915569 100644
--- a/drivers/i2c/busses/i2c-rcar.c
+++ b/drivers/i2c/busses/i2c-rcar.c
@@ -85,6 +85,7 @@
 /* ICFBSCR */
 #define TCYC17	0x0f		/* 17*Tcyc delay 1st bit between SDA and SCL */
 
+#define RCAR_MIN_DMA_LEN	8
 
 #define RCAR_BUS_PHASE_START	(MDBS | MIE | ESG)
 #define RCAR_BUS_PHASE_DATA	(MDBS | MIE)
@@ -412,8 +413,8 @@ static void rcar_i2c_dma(struct rcar_i2c_priv *priv)
 	int len;
 
 	/* Do various checks to see if DMA is feasible at all */
-	if (IS_ERR(chan) || msg->len < 8 || !(msg->flags & I2C_M_DMA_SAFE) ||
-	    (read && priv->flags & ID_P_NO_RXDMA))
+	if (IS_ERR(chan) || msg->len < RCAR_MIN_DMA_LEN ||
+	    !(msg->flags & I2C_M_DMA_SAFE) || (read && priv->flags & ID_P_NO_RXDMA))
 		return;
 
 	if (read) {
@@ -921,6 +922,9 @@ static int rcar_i2c_probe(struct platform_device *pdev)
 	struct i2c_timings i2c_t;
 	int irq, ret;
 
+	/* Otherwise logic will break because some bytes must always use PIO */
+	BUILD_BUG_ON_MSG(RCAR_MIN_DMA_LEN < 3, "Invalid min DMA length");
+
 	priv = devm_kzalloc(dev, sizeof(struct rcar_i2c_priv), GFP_KERNEL);
 	if (!priv)
 		return -ENOMEM;
-- 
2.11.0




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