From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932687Ab2C1S0p (ORCPT ); Wed, 28 Mar 2012 14:26:45 -0400 Received: from mail-gy0-f202.google.com ([209.85.160.202]:54957 "EHLO mail-gy0-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932376Ab2C1S0n (ORCPT ); Wed, 28 Mar 2012 14:26:43 -0400 From: Daniel Kurtz To: Daniel Vetter , Keith Packard , David Airlie , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Cc: Benson Leung , Yufeng Shen , Daniel Kurtz Subject: [PATCH 1/7 v6] drm/i915/intel_i2c: handle zero-length writes Date: Thu, 29 Mar 2012 02:26:33 +0800 Message-Id: <1332959199-32161-2-git-send-email-djkurtz@chromium.org> X-Mailer: git-send-email 1.7.7.3 In-Reply-To: <1332959199-32161-1-git-send-email-djkurtz@chromium.org> References: <1332959199-32161-1-git-send-email-djkurtz@chromium.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org A common method of probing an i2c bus is trying to do a zero-length write. Handle this case by checking the length first before decrementing it. This is actually important, since attempting a zero-length write is one of the ways that i2cdetect and i2c_new_probed_device detect whether there is device present on the bus with a given address. Signed-off-by: Daniel Kurtz --- drivers/gpu/drm/i915/intel_i2c.c | 7 ++++--- 1 files changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c index c12db72..99a04f8 100644 --- a/drivers/gpu/drm/i915/intel_i2c.c +++ b/drivers/gpu/drm/i915/intel_i2c.c @@ -248,9 +248,10 @@ gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg, u32 val, loop; val = loop = 0; - do { - val |= *buf++ << (8 * loop); - } while (--len && ++loop < 4); + while (len && loop < 4) { + val |= *buf++ << (8 * loop++); + len -= 1; + } I915_WRITE(GMBUS3 + reg_offset, val); I915_WRITE(GMBUS1 + reg_offset, -- 1.7.7.3