From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753520Ab2DMLsE (ORCPT ); Fri, 13 Apr 2012 07:48:04 -0400 Received: from mail-lpp01m010-f74.google.com ([209.85.215.74]:49558 "EHLO mail-lpp01m010-f74.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751080Ab2DMLsB (ORCPT ); Fri, 13 Apr 2012 07:48:01 -0400 From: Daniel Kurtz To: Keith Packard , David Airlie , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Daniel Vetter , Chris Wilson Cc: Daniel Kurtz Subject: [PATCH 1/2] drm/i915/intel_i2c: handle zero-length reads Date: Fri, 13 Apr 2012 19:47:53 +0800 Message-Id: <1334317674-32450-1-git-send-email-djkurtz@chromium.org> X-Mailer: git-send-email 1.7.7.3 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 read. Handle this case by checking the length first waiting for data to be read. This is actually important, since attempting a zero-length read 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 | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c index cab879f..e249160 100644 --- a/drivers/gpu/drm/i915/intel_i2c.c +++ b/drivers/gpu/drm/i915/intel_i2c.c @@ -217,7 +217,7 @@ gmbus_xfer_read(struct drm_i915_private *dev_priv, struct i2c_msg *msg, (len << GMBUS_BYTE_COUNT_SHIFT) | (msg->addr << GMBUS_SLAVE_ADDR_SHIFT) | GMBUS_SLAVE_READ | GMBUS_SW_RDY); - do { + while (len) { int ret; u32 val, loop = 0; u32 gmbus2; @@ -235,7 +235,7 @@ gmbus_xfer_read(struct drm_i915_private *dev_priv, struct i2c_msg *msg, *buf++ = val & 0xff; val >>= 8; } while (--len && ++loop < 4); - } while (len); + } return 0; } -- 1.7.7.3