From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:45704 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750830AbdAQQNw (ORCPT ); Tue, 17 Jan 2017 11:13:52 -0500 Subject: Patch "i2c: mux: pca954x: fix i2c mux selection caching" has been added to the 4.9-stable tree To: rmk+kernel@armlinux.org.uk, gregkh@linuxfoundation.org, peda@axentia.se, wsa@the-dreams.de Cc: , From: Date: Tue, 17 Jan 2017 17:12:56 +0100 Message-ID: <1484669576114146@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled i2c: mux: pca954x: fix i2c mux selection caching to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: i2c-mux-pca954x-fix-i2c-mux-selection-caching.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 7f638c1cb0a1112dbe0b682a42db30521646686b Mon Sep 17 00:00:00 2001 From: Russell King Date: Sat, 17 Dec 2016 12:10:56 +0000 Subject: i2c: mux: pca954x: fix i2c mux selection caching 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 Signed-off-by: Greg Kroah-Hartman --- 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 @@ -151,6 +151,9 @@ static int pca954x_reg_write(struct i2c_ 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 i2 /* 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; Patches currently in stable-queue which might be from rmk+kernel@armlinux.org.uk are queue-4.9/i2c-mux-pca954x-fix-i2c-mux-selection-caching.patch