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[ Upstream commit 0e148a522b8453115038193e19ec7bea71403e4a ] The code ignored the I2C_M_RD flag on I2C messages. Instead it assumed an i2c transaction with a single message must be a write operation and a transaction with two messages would be a read operation. Though this works for the driver code, it leads to problems once the i2c device is exposed to code not knowing this convention. For example, I did "insmod i2c-dev" and issued read requests from userspace, which were translated into write requests and destroyed the EEPROM of my device. So, just check and respect the I2C_M_READ flag, which indicates a read when set on a message. If it is absent, it is a write message. Incidentally, changing from the case statement to a while loop allows the code to lift the limitation to two i2c messages per transaction. There are 4 more *_i2c_transfer functions affected by the same behaviour and limitation that should be fixed in the same way. Link: https://lore.kernel.org/linux-media/20220116112238.74171-2-micha@freedict.org Signed-off-by: Michael Bunk <micha@freedict.org> Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> (cherry picked from commit 74eb7ec7afe976a499484f56e8af020c3260a559) Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.