[PATCH 3/3] i2c: mux: pca954x: Report deselect failures

[Bart Van Assche <bvanassche@acm.org>]

The i2c-mux core ignores the return value of the deselect callback.
Hence, if programming the mux into its idle state fails, the failure
goes unnoticed and a channel may remain connected until the next
transfer reprograms the mux. Log a rate-limited warning if
pca954x_deselect_mux() fails.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/i2c/muxes/i2c-mux-pca954x.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c
index 91df2d2fa2b7..45a7d841e7cf 100644
--- a/drivers/i2c/muxes/i2c-mux-pca954x.c
+++ b/drivers/i2c/muxes/i2c-mux-pca954x.c
@@ -359,7 +359,21 @@ static int pca954x_set_idle_state(struct i2c_mux_core *muxc)
 
 static int pca954x_deselect_mux(struct i2c_mux_core *muxc, u32 chan)
 {
-	return pca954x_set_idle_state(muxc);
+	struct pca954x *data = i2c_mux_priv(muxc);
+	int ret;
+
+	ret = pca954x_set_idle_state(muxc);
+	/*
+	 * The i2c-mux core ignores the deselect return value. Report failures
+	 * since these may leave a channel connected until the next transfer
+	 * reprograms the mux.
+	 */
+	if (ret < 0)
+		dev_warn_ratelimited(&data->client->dev,
+				     "failed to deselect channel %u: %d\n",
+				     chan, ret);
+
+	return ret;
 }
 
 static ssize_t idle_state_show(struct device *dev,