kernel/linux.git/drivers/tty/n_tty.c, branch v6.18.21

tty: n_tty: move more_to_be_read to the end of n_tty_read()

2025-03-20T15:00:51+00:00

n_tty_read() contains "we need more data" handling deep in that function. And there is also a label (more_to_be_read) as we handle this situation from two places. It makes more sense to have all "return"s accumulated at the end of functions. And "goto" from multiple places there. Therefore, do this with the "more_to_be_read" label in n_tty_read(). After this and the previous changes, n_tty_read() is now much more easier to follow. Signed-off-by: Jiri Slaby (SUSE) Link: https://lore.kernel.org/r/20250317070046.24386-12-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

tty: n_tty: extract n_tty_wait_for_input()

2025-03-20T15:00:51+00:00

n_tty_read() is a very long function doing too much of different stuff. Extract the "wait for input" to a separate function: n_tty_wait_for_input(). It returns an error (< 0), no input (0), or has potential input (1). Signed-off-by: Jiri Slaby (SUSE) Link: https://lore.kernel.org/r/20250317070046.24386-11-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

tty: n_tty: extract n_tty_continue_cookie() from n_tty_read()

2025-03-20T15:00:50+00:00

n_tty_read() is a very long function doing too much of different stuff. Extract the "cookie" (continuation read) handling to a separate function: n_tty_continue_cookie(). Signed-off-by: Jiri Slaby (SUSE) Link: https://lore.kernel.org/r/20250317070046.24386-10-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

tty: n_tty: drop n_tty_trace()

2025-03-20T15:00:50+00:00

This n_tty_trace() is an always disabled debugging macro. It comes from commit 32f13521ca68 ("n_tty: Line copy to user buffer in canonical mode"). Drop it as it is dead for over a decade. Signed-off-by: Jiri Slaby (SUSE) Link: https://lore.kernel.org/r/20250317070046.24386-9-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

tty: n_tty: clean up process_output_block()

2025-03-20T15:00:50+00:00

* Use guard(mutex), which results in: - the function can return directly when "space == 0". - "i" can now be "unsigned" as it is no longer abused to hold a retval from tty->ops->write(). Note the compared-to "nr" is already "unsigned". * The end label is now dubbed "do_write" as that is what happens there. Unlike the uncertain "break_out" name. Signed-off-by: Jiri Slaby (SUSE) Link: https://lore.kernel.org/r/20250317070046.24386-8-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

tty: n_tty: simplify process_output()

2025-03-20T15:00:50+00:00

Using guard(mutex), the function can be written in a much more efficient way. Signed-off-by: Jiri Slaby (SUSE) Link: https://lore.kernel.org/r/20250317070046.24386-7-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

tty: n_tty: use uint for space returned by tty_write_room()

2025-03-20T15:00:50+00:00

tty_write_room() returns an "unsigned int". So in case some insane driver (like my tty test driver) returns (legitimate) UINT_MAX from its tty_operations::write_room(), n_tty is confused on several places. For example, in process_output_block(), the result of tty_write_room() is stored into (signed) "int". So this UINT_MAX suddenly becomes -1. And that is extended to ssize_t and returned from process_output_block(). This causes a write() to such a node to receive -EPERM (which is -1). Fix that by using proper "unsigned int" and proper "== 0" test. And return 0 constant directly in that "if", so that it is immediately clear what is returned ("space" equals to 0 at that point). Similarly for process_output() and __process_echoes(). Note this does not fix any in-tree driver as of now. If you want "Fixes: something", it would be commit 03b3b1a2405c ("tty: make tty_operations::write_room return uint"). I intentionally do not mark this patch by a real tag below. Signed-off-by: Jiri Slaby (SUSE) Link: https://lore.kernel.org/r/20250317070046.24386-6-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

tty: move N_TTY_BUF_SIZE to n_tty

2025-03-20T15:00:50+00:00

"N_TTY_BUF_SIZE" is private to n_tty and shall not be exposed to the world. Definitely not in tty.h somewhere in the middle of "struct tty_struct". This is a remnant of moving "read_flags" to "struct n_tty_data" in commit 3fe780b379fa ("TTY: move ldisc data from tty_struct: bitmaps"). But some cleanup was needed first (in previous patches). Signed-off-by: Jiri Slaby (SUSE) Link: https://lore.kernel.org/r/20250317070046.24386-5-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

tty: n_tty: Fix buffer offsets when lookahead is used

2024-06-04T12:07:27+00:00

When lookahead has "consumed" some characters (la_count > 0), n_tty_receive_buf_standard() and n_tty_receive_buf_closing() for characters beyond the la_count are given wrong cp/fp offsets which leads to duplicating and losing some characters. If la_count > 0, correct buffer pointers and make count consistent too (the latter is not strictly necessary to fix the issue but seems more logical to adjust all variables immediately to keep state consistent). Reported-by: Vadym Krevs Fixes: 6bb6fa6908eb ("tty: Implement lookahead to process XON/XOFF timely") Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218834 Tested-by: Vadym Krevs Cc: stable@vger.kernel.org Signed-off-by: Ilpo Järvinen Link: https://lore.kernel.org/r/20240514140429.12087-1-ilpo.jarvinen@linux.intel.com Signed-off-by: Greg Kroah-Hartman

tty: invert return values of tty_{,un}throttle_safe()

2023-10-03T12:31:15+00:00

If tty_{,un}throttle_safe() returned true on success (similar to *_trylock()), it would make the conditions in callers more obvious. So perform the switch to these inverted values (and fix the callers). Signed-off-by: "Jiri Slaby (SUSE)" Link: https://lore.kernel.org/r/20230919085156.1578-8-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman