From: Wolfram Sang <wsa@the-dreams.de>
To: Pontus Andersson <epontan@gmail.com>
Cc: Seth Heasley <seth.heasley@intel.com>,
Neil Horman <nhorman@tuxdriver.com>,
linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] i2c: ismt: Separate I2C block read from SMBus block read
Date: Thu, 5 Oct 2017 14:41:33 +0200 [thread overview]
Message-ID: <20171005124133.7ue727bib2mlpnyy@ninjato> (raw)
In-Reply-To: <20171002124519.GA13496@leonis.localdomain>
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On Mon, Oct 02, 2017 at 02:45:19PM +0200, Pontus Andersson wrote:
> Commit b6c159a9cb69 ("i2c: ismt: Don't duplicate the receive length for
> block reads") broke I2C block reads. It aimed to fix normal SMBus block
> read, but changed the correct behavior of I2C block read in the process.
>
> According to Documentation/i2c/smbus-protocol, one vital difference
> between normal SMBus block read and I2C block read is that there is no
> byte count prefixed in the data sent on the wire:
>
> SMBus Block Read: i2c_smbus_read_block_data()
> S Addr Wr [A] Comm [A]
> S Addr Rd [A] [Count] A [Data] A [Data] A ... A [Data] NA P
>
> I2C Block Read: i2c_smbus_read_i2c_block_data()
> S Addr Wr [A] Comm [A]
> S Addr Rd [A] [Data] A [Data] A ... A [Data] NA P
>
> Therefore the two transaction types need to be processed differently in
> the driver by copying of the dma_buffer as done previously for the
> I2C_SMBUS_I2C_BLOCK_DATA case.
>
> Fixes: b6c159a9cb69 ("i2c: ismt: Don't duplicate the receive length for block reads")
> Signed-off-by: Pontus Andersson <epontan@gmail.com>
> Cc: stable@vger.kernel.org
Applied to for-current, thanks!
Might have been good to CC the patch author of the problematic commit,
too.
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next prev parent reply other threads:[~2017-10-05 12:41 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-02 12:45 [PATCH] i2c: ismt: Separate I2C block read from SMBus block read Pontus Andersson
2017-10-05 12:41 ` Wolfram Sang [this message]
2017-10-05 14:13 ` Pontus Andersson
2017-10-06 22:54 ` Stephen Douthit
2017-10-07 8:14 ` Wolfram Sang
[not found] ` <c9a1d377-1a72-a1fa-304a-48d593d48e6b@adiengineering.com>
2017-10-09 17:18 ` Stephen Douthit
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