From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9C4E0C433DF for ; Mon, 15 Jun 2020 09:40:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 857FC2065F for ; Mon, 15 Jun 2020 09:40:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729213AbgFOJk0 (ORCPT ); Mon, 15 Jun 2020 05:40:26 -0400 Received: from mga14.intel.com ([192.55.52.115]:28925 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728411AbgFOJk0 (ORCPT ); Mon, 15 Jun 2020 05:40:26 -0400 IronPort-SDR: MEy6tbFepUDj348cFVI4zdq+A2doPimbzZmpWRjWjw6vgo/k0snuPDunjRAGHvs+7cH6AXdKec Jo9xc/WvPJWQ== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Jun 2020 02:40:23 -0700 IronPort-SDR: LHQqZ76Fn7bIbBFT7Zn7EpEOpc4QRKtaF80t6uGidUtlRfn4y7YzJbrBh+rgoQ+f/DrYLdkEsI sbi6SZmcyNeA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,514,1583222400"; d="scan'208";a="276501595" Received: from smile.fi.intel.com (HELO smile) ([10.237.68.40]) by orsmga006.jf.intel.com with ESMTP; 15 Jun 2020 02:40:17 -0700 Received: from andy by smile with local (Exim 4.94) (envelope-from ) id 1jklbH-00DXN0-GZ; Mon, 15 Jun 2020 12:40:19 +0300 Date: Mon, 15 Jun 2020 12:40:19 +0300 From: Andy Shevchenko To: Sultan Alsawaf Cc: Aaron Ma , Benjamin Tissoires , Hans de Goede , HungNien Chen , Jarkko Nikula , Jiri Kosina , Kai-Heng Feng , linux-i2c@vger.kernel.org, linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, Mika Westerberg , Pavel Balan , Tin Huynh , Wolfram Sang , You-Sheng Yang Subject: Re: [PATCH 1/2] i2c: designware: Only check the first byte for SMBus block read length Message-ID: <20200615094019.GP2428291@smile.fi.intel.com> References: <20200614210255.4641-1-sultan@kerneltoast.com> <20200614210255.4641-2-sultan@kerneltoast.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200614210255.4641-2-sultan@kerneltoast.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Sender: linux-input-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-input@vger.kernel.org On Sun, Jun 14, 2020 at 02:02:54PM -0700, Sultan Alsawaf wrote: > From: Sultan Alsawaf > > SMBus block reads can be broken because the read function will just skip > over bytes it doesn't like until reaching a byte that conforms to the > length restrictions for block reads. This is problematic when it isn't > known if the incoming payload is indeed a conforming block read. > > According to the SMBus specification, block reads will only send the > payload length in the first byte, so we can fix this by only considering > the first byte in a sequence for block read length purposes. I'm wondering if this overlaps with [1]. AFAIU that one is also makes sure that the length is not a garbage. [1]: https://lore.kernel.org/linux-i2c/20200613104109.2989-1-mans@mansr.com/T/#u > Fixes: c3ae106050b9 ("i2c: designware: Implement support for SMBus block read and write") > Signed-off-by: Sultan Alsawaf > --- > drivers/i2c/busses/i2c-designware-master.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-designware-master.c b/drivers/i2c/busses/i2c-designware-master.c > index d6425ad6e6a3..16d38b8fc19a 100644 > --- a/drivers/i2c/busses/i2c-designware-master.c > +++ b/drivers/i2c/busses/i2c-designware-master.c > @@ -398,7 +398,6 @@ i2c_dw_recv_len(struct dw_i2c_dev *dev, u8 len) > len += (flags & I2C_CLIENT_PEC) ? 2 : 1; > dev->tx_buf_len = len - min_t(u8, len, dev->rx_outstanding); > msgs[dev->msg_read_idx].len = len; > - msgs[dev->msg_read_idx].flags &= ~I2C_M_RECV_LEN; > > return len; > } > @@ -430,10 +429,11 @@ i2c_dw_read(struct dw_i2c_dev *dev) > u32 flags = msgs[dev->msg_read_idx].flags; > > regmap_read(dev->map, DW_IC_DATA_CMD, &tmp); > - /* Ensure length byte is a valid value */ > - if (flags & I2C_M_RECV_LEN && > - tmp <= I2C_SMBUS_BLOCK_MAX && tmp > 0) { > - len = i2c_dw_recv_len(dev, tmp); > + if (flags & I2C_M_RECV_LEN) { > + /* Ensure length byte is a valid value */ > + if (tmp <= I2C_SMBUS_BLOCK_MAX && tmp > 0) > + len = i2c_dw_recv_len(dev, tmp); > + msgs[dev->msg_read_idx].flags &= ~I2C_M_RECV_LEN; > } > *buf++ = tmp; > dev->rx_outstanding--; > -- > 2.27.0 > -- With Best Regards, Andy Shevchenko