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Message-Id: <1332772010-19619-8-git-send-email-djkurtz@chromium.org>
Date: Mon, 26 Mar 2012 22:26:46 +0800
From: Daniel Kurtz <djkurtz@...omium.org>
To: Keith Packard <keithp@...thp.com>, David Airlie <airlied@...ux.ie>,
dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
Daniel Vetter <daniel@...ll.ch>,
Chris Wilson <chris@...is-wilson.co.uk>
Cc: Benson Leung <bleung@...omium.org>,
Yufeng Shen <miletus@...omium.org>,
Daniel Kurtz <djkurtz@...omium.org>
Subject: [PATCH 07/11 v3] drm/i915/intel_i2c: handle zero-length writes
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 <djkurtz@...omium.org>
---
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 a04f773..c467a2e 100644
--- a/drivers/gpu/drm/i915/intel_i2c.c
+++ b/drivers/gpu/drm/i915/intel_i2c.c
@@ -258,9 +258,10 @@ gmbus_xfer(struct i2c_adapter *adapter,
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
--
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