Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S937775AbdCJOIw (ORCPT ); Fri, 10 Mar 2017 09:08:52 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:42909 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933317AbdCJLvX (ORCPT ); Fri, 10 Mar 2017 06:51:23 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Russell King" , "Wolfram Sang" , "Peter Rosin" Date: Fri, 10 Mar 2017 11:46:22 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 117/370] i2c: mux: pca954x: fix i2c mux selection caching In-Reply-To: X-SA-Exim-Connect-IP: 82.70.136.246 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1853 Lines: 51 3.16.42-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Russell King commit 7f638c1cb0a1112dbe0b682a42db30521646686b upstream. 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 Signed-off-by: Wolfram Sang [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings --- drivers/i2c/muxes/i2c-mux-pca954x.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/drivers/i2c/muxes/i2c-mux-pca954x.c +++ b/drivers/i2c/muxes/i2c-mux-pca954x.c @@ -133,6 +133,9 @@ static int pca954x_reg_write(struct i2c_ buf[0] = val; msg.buf = buf; ret = adap->algo->master_xfer(adap, &msg, 1); + + if (ret >= 0 && ret != 1) + ret = -EREMOTEIO; } else { union i2c_smbus_data data; ret = adap->algo->smbus_xfer(adap, client->addr, @@ -161,7 +164,7 @@ static int pca954x_select_chan(struct i2 /* Only select the channel if its different from the last channel */ if (data->last_chan != regval) { ret = pca954x_reg_write(adap, client, regval); - data->last_chan = ret ? 0 : regval; + data->last_chan = ret < 0 ? 0 : regval; } return ret;