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f64d74a59c
The TIOCGSERIAL ioctl can be used to set and retrieve the UART type for legacy UARTs, but some USB serial drivers have been reporting back random types in order to "make user-space happy". Some applications have historically expected TIOCGSERIAL to be implemented, but judging from the Debian sources, the port type not being PORT_UNKNOWN is only used to check for the existence of legacy serial ports (ttySn). Drivers like ftdi_sio have been using PORT_UNKNOWN for twenty years (and option for 10 years) without anyone complaining so let's stop reporting back anything else. In the unlikely event that this do cause problems, this should be fixed tree-wide anyway (e.g. for all USB serial drivers and also CDC-ACM). Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Johan Hovold <johan@kernel.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.