8275b48b27
Many serial drivers do the same thing: * send x_char if set * keep sending from the xmit circular buffer until either - the loop reaches the end of the xmit buffer - TX is stopped - HW fifo is full * check for pending characters and: - wake up tty writers to fill for more data into xmit buffer - stop TX if there is nothing in the xmit buffer The only differences are: * how to write the character to the HW fifo * the check of the end condition: - is the HW fifo full? - is limit of the written characters reached? So unify the above into two helpers: * uart_port_tx_limited() -- it performs the above taking the written characters limit into account, and * uart_port_tx() -- the same as above, except it only checks the HW readiness, not the characters limit. The HW specific operations (as stated as "differences" above) are passed as arguments to the macros. They are: * tx_ready -- returns true if HW can accept more data. * put_char -- write a character to the device. * tx_done -- when the write loop is done, perform arbitrary action before potential invocation of ops->stop_tx() happens. Note that the above are macros. This means the code is generated in place and the above 3 arguments are "inlined". I.e. no added penalty by generating call instructions for every single character. Nor any indirect calls. (As in some previous versions of this patchset.) Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org> Link: https://lore.kernel.org/r/20221004104927.14361-2-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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.