From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754934AbbBTPXy (ORCPT ); Fri, 20 Feb 2015 10:23:54 -0500 Received: from ns.pmeerw.net ([84.19.176.92]:51263 "EHLO pmeerw.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754392AbbBTPXw (ORCPT ); Fri, 20 Feb 2015 10:23:52 -0500 Date: Fri, 20 Feb 2015 16:23:48 +0100 (CET) From: Peter Meerwald To: "Pandruvada, Srinivas" cc: "Tirdea, Irina" , "linux-kernel@vger.kernel.org" , "jic23@kernel.org" , "Reus, Adriana" , "linux-iio@vger.kernel.org" Subject: Re: [PATCH 2/2] iio: accel: kxcjk-1013: optimize i2c transfers in trigger handler In-Reply-To: <1424444331.2916.2.camel@spandruv-mobl2> Message-ID: References: <1424110909-16878-1-git-send-email-irina.tirdea@intel.com> <1424110909-16878-3-git-send-email-irina.tirdea@intel.com> <1F3AC3675D538145B1661F571FE1805F19A20D9C@irsmsx105.ger.corp.intel.com> <1424444331.2916.2.camel@spandruv-mobl2> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > > > + > > > > + values[i] = data & 0xFF; > > > > + values[i+1] = data >> 8; > > > > > > this is incorrect; it forces the data to be little endian, however, the > > > endianness (as specified in the driver's .scan_type) is IIO_CPU -- the > > > code breaks for big-endian CPUs > > > > > > since _read_i2c_block_data() can't do endianness conversion (and the chip > > > does i2c endianness, i.e. little-endian), the .scan_type should become > > > IIO_LE and above code is correct again but still ugly :) > > > > > > bottom line: change .scan_type to IIO_LE > > > > > Good point. Changing the endianess to IIO_LE is correct for either kxcjk1013_read_block_data or i2c_smbus_read_i2c_block_data. > > Will fix this in the next version. Thanks for catching this! > > > I don't think changing to IIO_LE is good idea as when i2c_read_bock.. > then the scan type will be CPU. So better to fix endianness in this > function. the chip has little-endian data registers; i2c_read_block() just transfers the data (no endianness conversion), so the data will still be little-endian p. -- Peter Meerwald +43-664-2444418 (mobile)