From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailgw01.mediatek.com (mailgw01.mediatek.com [210.61.82.183]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4001A1A0DC4 for ; Fri, 16 Jan 2015 19:23:47 +1100 (AEDT) Subject: Re: [RFC 01/11] i2c: add quirk structure to describe adapter flaws From: Yingjoe Chen To: Wolfram Sang In-Reply-To: <1420824103-24169-2-git-send-email-wsa@the-dreams.de> References: <1420824103-24169-1-git-send-email-wsa@the-dreams.de> <1420824103-24169-2-git-send-email-wsa@the-dreams.de> Content-Type: text/plain; charset="UTF-8" Date: Fri, 16 Jan 2015 16:18:15 +0800 Message-ID: <1421396295.11671.50.camel@mtksdaap41> MIME-Version: 1.0 Cc: Xudong Chen , linux-mips@linux-mips.org, linux-kernel@vger.kernel.org, Liguo Zhang , Ludovic Desroches , linux-i2c@vger.kernel.org, Eddie Huang , linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Fri, 2015-01-09 at 18:21 +0100, Wolfram Sang wrote: > The number of I2C adapters which are not fully I2C compatible is rising, > sadly. Drivers usually do handle the flaws, still the user receives only > some errno for a transfer which normally can be expected to work. This > patch introduces a formal description of flaws. One advantage is that > the core can check before the actual transfer if the messages could be > transferred at all. This is done in the next patch. Another advantage is > that we can pass this information to the user so the restrictions are > exactly known and further actions can be based on that. This will be > done later after some stabilization period for this description. Hi Wolfram, This can describe the behavior of our current upstream driver[1], which only support combine write-then-read. After checking with Xudong & HW guys, it seems our HW can do more. On MT8135, it can support at most 2 messages, no matter read or write, with the limitation that the length of the second message must <= 31bytes. So this RFC is enough for our driver, but it would be better if we could also support other case. Joe.C [1]: http://lists.infradead.org/pipermail/linux-arm-kernel/2014-November/305468.html