From mboxrd@z Thu Jan 1 00:00:00 1970 From: Antonio Borneo Subject: Re: [PATCH v2] HID: cp2112: support i2c write-read transfers in hid-cp2112 Date: Tue, 14 Jul 2015 18:09:57 +0800 Message-ID: References: <1436504106-31740-1-git-send-email-ellen@cumulusnetworks.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: Received: from mail-oi0-f50.google.com ([209.85.218.50]:35689 "EHLO mail-oi0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754612AbbGNKJ5 (ORCPT ); Tue, 14 Jul 2015 06:09:57 -0400 In-Reply-To: Sender: linux-input-owner@vger.kernel.org List-Id: linux-input@vger.kernel.org To: Jiri Kosina Cc: Ellen Wang , David Barksdale , linux-input , linux-i2c@vger.kernel.org On Fri, Jul 10, 2015 at 5:21 PM, Jiri Kosina wrote: > On Thu, 9 Jul 2015, Ellen Wang wrote: > >> cp2112_i2c_xfer() only supports a single i2c_msg. More than >> one message at a time just returns EIO. This breaks certain >> important cases. For example, the at24 eeprom driver generates >> paired write and read messages (for eeprom address and data). >> >> Since the device doesn't support i2c repeated starts in general, >> but does support a single write-repeated-start-read pair >> (since hardware rev 1), we recognize the latter case and >> implement only that. >> >> Signed-off-by: Ellen Wang > > Applied to for-4.3/cp2112. > Good! Either Tested-by: Antonio Borneo and/or Reviewed-by: Antonio Borneo By the way, while this patch extends the i2c functionality, it makes clear that repeated start is always broken on HW rev 1, also for SMBUS! I'm testing a patch to restrict SMBUS on rev 1 to only those transactions that don't require repeated start. Will post it shortly. Regards, Antonio