383f0993fc
Currently, the CAN netlink interface provides no easy ways to check the capabilities of a given controller. The only method from the command line is to try each CAN_CTRLMODE_* individually to check whether the netlink interface returns an -EOPNOTSUPP error or not (alternatively, one may find it easier to directly check the source code of the driver instead...) This patch introduces a method for the user to check both the supported and the static capabilities. The proposed method introduces a new IFLA nest: IFLA_CAN_CTRLMODE_EXT which extends the current IFLA_CAN_CTRLMODE. This is done to guaranty a full forward and backward compatibility between the kernel and the user land applications. The IFLA_CAN_CTRLMODE_EXT nest contains one single entry: IFLA_CAN_CTRLMODE_SUPPORTED. Because this entry is only used in one direction: kernel to userland, no new struct nla_policy are introduced. Below table explains how IFLA_CAN_CTRLMODE_SUPPORTED (hereafter: "supported") and can_ctrlmode::flags (hereafter: "flags") allow us to identify both the supported and the static capabilities, when masked with any of the CAN_CTRLMODE_* bit flags: supported & flags & Controller capabilities CAN_CTRLMODE_* CAN_CTRLMODE_* ----------------------------------------------------------------------- false false Feature not supported (always disabled) false true Static feature (always enabled) true false Feature supported but disabled true true Feature supported and enabled Link: https://lore.kernel.org/all/20211213160226.56219-5-mailhol.vincent@wanadoo.fr Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr> Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
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.