drivers: mbox_nxp_imx_mu: change send to return negative error

Change nxp_imx_mu_send() to return a negative errno value
on error.

The fsl_mu function MU_TriggerInterrupts() returns either
kStatus_Success or kStatus_Fail, which have the value 0
or 1, respectively. kStatus_Fail should not be returned
to the upper levels, which expect negative values for
errors, so add a check for the return value of
MU_TriggerInterrupts() and return an errno value on error.

Signed-off-by: mjchen0 <[email protected]>

Author: mjchen0

drivers/mbox/mbox_nxp_imx_mu.c

@@ -61,7 +61,12 @@ static int nxp_imx_mu_send(const struct device *dev, uint32_t channel, const str
 
 	/* Signalling mode. */
 	if (msg == NULL) {
-		return MU_TriggerInterrupts(cfg->base, g_gen_int_trig_mask[channel]);
+		int ret = MU_TriggerInterrupts(cfg->base, g_gen_int_trig_mask[channel]);
+		if (ret != 0) {
+			/* interrupt already pending, cannot trigger again */
+			return -EAGAIN;
+		}
+		return ret;
 	}
 
 	/* Data transfer mode. */