From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King Subject: [PATCH] i2c: mux: pca954x: fix i2c mux selection caching Date: Sat, 17 Dec 2016 12:10:56 +0000 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Return-path: Received: from pandora.armlinux.org.uk ([78.32.30.218]:42660 "EHLO pandora.armlinux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752619AbcLQMLC (ORCPT ); Sat, 17 Dec 2016 07:11:02 -0500 Content-Disposition: inline Sender: linux-i2c-owner@vger.kernel.org List-Id: linux-i2c@vger.kernel.org To: Wolfram Sang Cc: Peter Rosin , linux-i2c@vger.kernel.org smbus functions return -ve on error, 0 on success. However, __i2c_transfer() have a different return signature - -ve on error, or number of buffers transferred (which may be zero or greater.) The upshot of this is that the sense of the test is reversed when using the mux on a bus supporting the master_xfer method: we cache the value and never retry if we fail to transfer any buffers, but if we succeed, we clear the cached value. Fix this by making pca954x_reg_write() return a negative error code for all failure cases. Fixes: 463e8f845cbf ("i2c: mux: pca954x: retry updating the mux selection on failure") Acked-by: Peter Rosin Signed-off-by: Russell King --- drivers/i2c/muxes/i2c-mux-pca954x.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c index 8bc3d36d2837..9c4ac26c014e 100644 --- a/drivers/i2c/muxes/i2c-mux-pca954x.c +++ b/drivers/i2c/muxes/i2c-mux-pca954x.c @@ -151,6 +151,9 @@ static int pca954x_reg_write(struct i2c_adapter *adap, buf[0] = val; msg.buf = buf; ret = __i2c_transfer(adap, &msg, 1); + + if (ret >= 0 && ret != 1) + ret = -EREMOTEIO; } else { union i2c_smbus_data data; ret = adap->algo->smbus_xfer(adap, client->addr, @@ -179,7 +182,7 @@ static int pca954x_select_chan(struct i2c_mux_core *muxc, u32 chan) /* Only select the channel if its different from the last channel */ if (data->last_chan != regval) { ret = pca954x_reg_write(muxc->parent, client, regval); - data->last_chan = ret ? 0 : regval; + data->last_chan = ret < 0 ? 0 : regval; } return ret; -- 2.7.4