Commit 2fac2b89 authored Jan 13, 2014 by Stephen Warren Committed by Wolfram Sang Jan 14, 2014

i2c: Re-instate body of i2c_parent_is_i2c_adapter()



The body of i2c_parent_is_i2c_adapter() is currently guarded by
I2C_MUX. It should be CONFIG_I2C_MUX instead.

Among potentially other problems, this resulted in i2c_lock_adapter()
only locking I2C mux child adapters, and not the parent adapter. In
turn, this could allow inter-mingling of mux child selection and I2C
transactions, which could result in I2C transactions being directed to
the wrong I2C bus, and possibly even switching between busses in the
middle of a transaction.

One concrete issue caused by this bug was corrupted HDMI EDID reads
during boot on the NVIDIA Tegra Seaboard system, although this only
became apparent in recent linux-next, when the boot timing was changed
just enough to trigger the race condition.

Fixes: 3923172b ("i2c: reduce parent checking to a NOOP in non-I2C_MUX case")
Cc: Phil Carmody <phil.carmody@partner.samsung.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

parent 7e22e911

include/linux/i2c.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -445,7 +445,7 @@ static inline void i2c_set_adapdata(struct i2c_adapter dev, void data)
		static inline struct i2c_adapter *
		i2c_parent_is_i2c_adapter(const struct i2c_adapter *adapter)
		{
		#if IS_ENABLED(I2C_MUX)
		#if IS_ENABLED(CONFIG_I2C_MUX)
		struct device *parent = adapter->dev.parent;

		if (parent != NULL && parent->type == &i2c_adapter_type)

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