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[ Upstream commit e2c68cea431d65292b592c9f8446c918d45fcf78 ]
Fix several issues with division of negative numbers in the tmp513
driver.
The docs on the DIV_ROUND_CLOSEST macro explain that dividing a negative
value by an unsigned type is undefined behavior. The driver was doing
this in several places, i.e. data->shunt_uohms has type of u32. The
actual "undefined" behavior is that it converts both values to unsigned
before doing the division, for example:
int ret = DIV_ROUND_CLOSEST(-100, 3U);
results in ret == 1431655732 instead of -33.
Furthermore the MILLI macro has a type of unsigned long. Multiplying a
signed long by an unsigned long results in an unsigned long.
So, we need to cast both MILLI and data data->shunt_uohms to long when
using the DIV_ROUND_CLOSEST macro.
Fixes: f07f9d2467f4 ("hwmon: (tmp513) Use SI constants from units.h")
Fixes: 59dfa75e5d ("hwmon: Add driver for Texas Instruments TMP512/513 sensor chips.")
Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://lore.kernel.org/r/20250114-fix-si-prefix-macro-sign-bugs-v1-1-696fd8d10f00@baylibre.com
[groeck: Drop some continuation lines]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
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.