From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756854Ab2C1Mwq (ORCPT ); Wed, 28 Mar 2012 08:52:46 -0400 Received: from mail-fa0-f74.google.com ([209.85.161.74]:63810 "EHLO mail-fa0-f74.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754360Ab2C1MwH (ORCPT ); Wed, 28 Mar 2012 08:52:07 -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 08/14 v5] drm/i915/intel_i2c: handle zero-length writes Date: Wed, 28 Mar 2012 20:51:51 +0800 Message-Id: <1332939117-6513-9-git-send-email-djkurtz@chromium.org> X-Mailer: git-send-email 1.7.7.3 In-Reply-To: <1332939117-6513-1-git-send-email-djkurtz@chromium.org> References: <1332939117-6513-1-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