The initcalls like to play joke. In our case, the thermal-netlink
initcall is called after the thermal-core initcall but this one sends
a notification before the former is initialized. No issue was spotted,
but it could lead to a memory corruption, so instead of relying on the
core_initcall for the thermal-netlink, let's initialize directly from
the thermal-core init routine, so we have full control of the init
ordering.
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Amit Kucheria <amit.kucheria@linaro.org>
Link: https://lore.kernel.org/r/20200717164217.18819-1-daniel.lezcano@linaro.org
The variable ret is being initialized with a value that is never read
and it is being updated later with a new value. The initialization is
redundant and can be removed.
Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200706140747.489075-1-colin.king@canonical.com
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
