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Currently there is no way for Realtek DSA subdrivers to serialize consecutive regmap accesses. In preparation for a bugfix relating to indirect PHY register access - which involves a series of regmap reads and writes - add a facility for subdrivers to serialize their regmap access. Specifically, a mutex is added to the driver private data structure and the standard regmap is initialized with custom lock/unlock ops which use this mutex. Then, a "nolock" variant of the regmap is added, which is functionally equivalent to the existing regmap except that regmap locking is disabled. Functions that wish to serialize a sequence of regmap accesses may then lock the newly introduced driver-owned mutex before using the nolock regmap. Doing things this way means that subdriver code that doesn't care about serialized register access - i.e. the vast majority of code - needn't worry about synchronizing register access with an external lock: it can just continue to use the original regmap. Another advantage of this design is that, while regmaps with locking disabled do not expose a debugfs interface for obvious reasons, there still exists the original regmap which does expose this interface. This interface remains safe to use even combined with driver codepaths that use the nolock regmap, because said codepaths will use the same mutex to synchronize access. With respect to disadvantages, it can be argued that having near-duplicate regmaps is confusing. However, the naming is rather explicit, and examples will abound. Finally, while we are at it, rename realtek_smi_mdio_regmap_config to realtek_smi_regmap_config. This makes it consistent with the naming realtek_mdio_regmap_config in realtek-mdio.c. Signed-off-by: Alvin Šipraga <alsi@bang-olufsen.dk> Reviewed-by: Vladimir Oltean <olteanv@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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.