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Initially the thermal framework had a very simple notification mechanism to send generic netlink messages to the userspace. The notification function was never called from anywhere and the corresponding dead code was removed. It was probably a first attempt to introduce the netlink notification. At LPC2018, the presentation "Linux thermal: User kernel interface", proposed to create the notifications to the userspace via a kfifo. The advantage of the kfifo is the performance. It is usually used from a 1:1 communication channel where a driver captures data and sends it as fast as possible to a userspace process. The drawback is that only one process uses the notification channel exclusively, thus no other process is allowed to use the channel to get temperature or notifications. This patch defines a generic netlink API to discover the current thermal setup and adds event notifications as well as temperature sampling. As any genetlink protocol, it can evolve and the versioning allows to keep the backward compatibility. In order to prevent the user from getting flooded with data on a single channel, there are two multicast channels, one for the temperature sampling when the thermal zone is updated and another one for the events, so the user can get the events only without the thermal zone temperature sampling. Also, a list of commands to discover the thermal setup is added and can be extended when needed. Reviewed-by: Amit Kucheria <amit.kucheria@linaro.org> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> Acked-by: Zhang Rui <rui.zhang@intel.com> Link: https://lore.kernel.org/r/20200706105538.2159-3-daniel.lezcano@linaro.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.