There's no need to include linux/tty_buffer.h in linux/tty.h.
Move the include into tty_buffer.c that is actually using it.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20240215111538.1920-1-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

It's a boolean value, so no need for 'int' there.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20230919085156.1578-12-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

We are used to handle "bad" states in the 'if's in the kernel. Refactor
(invert the two conditions in) __tty_buffer_request_room(), so that the
code returns from the fast paths immediately instead of postponing to
the heavy end of the function.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20230816105530.3335-11-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

It makes the code both more compact, and more understandable.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20230816105530.3335-10-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

* use bool for 'change' as it holds a result of a boolean.
* use size_t for 'left', so it is the same as 'size' which it is
  compared to. Both are supposed to contain an unsigned value.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20230816105530.3335-9-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Use __tty_insert_flip_string_flags() for the slow path of
tty_insert_flip_char(). The former is generic enough, so there is no
reason to reimplement the injection once again.

So now we have a single function stuffing into tty buffers.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20230816105530.3335-8-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The same as in the previous patch, tty_prepare_flip_string() accepts
size_t as an size argument. It returns the same size (or less). It is
unexpected that it returns a signed value and can confuse users to check
for negative values.

Instead, return the same size_t as accepted to make clear we return
values >= 0, where zero in fact means failure.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20230816105530.3335-7-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

All the functions accept size_t as a size argument. They finally return
the same size (or less). It is quite unexpected that they return a
signed value and can confuse users to check for negative values.

Instead, return the same size_t as accepted to make clear we return
values >= 0, where zero in fact means failure.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20230816105530.3335-6-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

And add a WARN_ON_ONCE(need_flags) to make sure we are not losing flags
in __tty_insert_flip_string_flags().

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20230816105530.3335-5-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

They both do the same except for flags. One mem-copies the flags from
the caller, the other mem-sets to one flag given by the caller. This can
be unified with a simple if in the unified function.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20230816105530.3335-4-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>