From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail.kapsi.fi ([217.30.184.167]:39741 "EHLO mail.kapsi.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756588Ab2LNQ4L (ORCPT ); Fri, 14 Dec 2012 11:56:11 -0500 Message-ID: <50CB5A0A.3030305@iki.fi> Date: Fri, 14 Dec 2012 18:55:38 +0200 From: Antti Palosaari MIME-Version: 1.0 To: =?UTF-8?B?RnJhbmsgU2Now6RmZXI=?= CC: mchehab@redhat.com, linux-media@vger.kernel.org, dheitmueller@kernellabs.com Subject: Re: [PATCH 2/5] em28xx: respect the message size constraints for i2c transfers References: <1355502533-25636-1-git-send-email-fschaefer.oss@googlemail.com> <1355502533-25636-3-git-send-email-fschaefer.oss@googlemail.com> In-Reply-To: <1355502533-25636-3-git-send-email-fschaefer.oss@googlemail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-media-owner@vger.kernel.org List-ID: On 12/14/2012 06:28 PM, Frank Schäfer wrote: > The em2800 can transfer up to 4 bytes per i2c message. > All other em25xx/em27xx/28xx chips can transfer at least 64 bytes per message. > > I2C adapters should never split messages transferred via the I2C subsystem > into multiple message transfers, because the result will almost always NOT be > the same as when the whole data is transferred to the I2C client in a single > message. > If the message size exceeds the capabilities of the I2C adapter, -EOPNOTSUPP > should be returned. > > Signed-off-by: Frank Schäfer > + if (len < 1 || len > 4) > + return -EOPNOTSUPP; That patch seem to be good for my eyes, but that check for len < 1 is something I would like to double checked. Generally len = 0 is OK and is used some cases, probing and sometimes when all registers are read for example. Did you test it returns some error for zero len messages? regards Antti -- http://palosaari.fi/