Re: [PATCH] i2c: Re-instate body of i2c_parent_is_i2c_adapter()

Stephen Warren
2014-01-16T17:25:37Z

On 01/14/2014 09:12 AM, Wolfram Sang wrote:
> On Mon, Jan 13, 2014 at 02:29:04PM -0700, Stephen Warren wrote:
>> From: Stephen Warren <swarren@nvidia.com>
>>
>> The body of i2c_parent_is_i2c_adapter() is currently guarded by
>> CONFIG_I2C_MUX instead.
>
> This paragraph sounds strange to me. I'll update it a little. After that
> I'll go looking for a brown paper bag...
>
>> 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: 3923172b3d70 ("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>
>
> Applied to for-current, thanks for catching this one!

I do see this in for-current, but it looks like that branch isn't part
of linux-next. Should it be, or perhaps for-current should be merged
into for-next?