i2c: rcar: sanity check for minimal DMA length

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@sang-engineering.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
index a7578f6..57083e9 100644 (file)
--- 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;