linux-stable.git/drivers/tty/n_tty.c, branch v6.4 Linux kernel stable tree n_tty: Reindent if condition 2023-03-17T14:01:09+00:00 Ilpo Järvinen ilpo.jarvinen@linux.intel.com 2023-03-09T08:20:34+00:00 37e8b08ada22f5cd4a8e94f6e783d00cd6e6d7e6 Align if condition to make it easier to read. Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> Link: https://lore.kernel.org/r/20230309082035.14880-8-ilpo.jarvinen@linux.intel.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
Align if condition to make it easier to read.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20230309082035.14880-8-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
n_tty: Cleanup includes 2023-03-17T14:01:09+00:00 Ilpo Järvinen ilpo.jarvinen@linux.intel.com 2023-03-09T08:20:33+00:00 8ed012d1be12c183e173c9e0933b34a7073a9c8a n_tty uses: - bitmap_zero() from linux/bitmap.h - EXPORT_SYMBOL_GPL() from linux/export.h - jiffies, time_after() from linux/jiffies.h Add includes. n_tty uses nothing from: - linux/audit.h - linux/interrupt.h - linux/major.h - linux/mm.h - linux/module.h - linux/timer.h Remove those includes. Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> Link: https://lore.kernel.org/r/20230309082035.14880-7-ilpo.jarvinen@linux.intel.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
n_tty uses:
	- bitmap_zero() from linux/bitmap.h
	- EXPORT_SYMBOL_GPL() from linux/export.h
	- jiffies, time_after() from linux/jiffies.h

Add includes.

n_tty uses nothing from:
	- linux/audit.h
	- linux/interrupt.h
	- linux/major.h
	- linux/mm.h
	- linux/module.h
	- linux/timer.h

Remove those includes.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20230309082035.14880-7-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
n_tty: Use DIV_ROUND_UP() in room calculation 2023-03-17T14:01:08+00:00 Ilpo Järvinen ilpo.jarvinen@linux.intel.com 2023-03-09T08:20:32+00:00 7e26c84d02d17e7412e6f2471916fd415654a1ba When PARMRK is set, a character can result in up to 3 chars in the read buffer. Receive code calculates for how many characters there (at least) is room. Convert an opencoded rounding in the calculation to use DIV_ROUND_UP(). Note: the room variable is decremented afterwards by one which ensures the characters will fit into the buffer for real so the code is okay despite rounding upwards. Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> Link: https://lore.kernel.org/r/20230309082035.14880-6-ilpo.jarvinen@linux.intel.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
When PARMRK is set, a character can result in up to 3 chars in the read
buffer. Receive code calculates for how many characters there (at
least) is room. Convert an opencoded rounding in the calculation to use
DIV_ROUND_UP().

Note: the room variable is decremented afterwards by one which ensures
the characters will fit into the buffer for real so the code is okay
despite rounding upwards.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20230309082035.14880-6-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
n_tty: Sort includes alphabetically 2023-03-17T14:01:08+00:00 Ilpo Järvinen ilpo.jarvinen@linux.intel.com 2023-03-09T08:20:31+00:00 9db1be84054b7445f911b9efe9bc3c924ffdb543 Sort includes in n_tty alphabetically to make it easier to see if an include is among the list or not. Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> Link: https://lore.kernel.org/r/20230309082035.14880-5-ilpo.jarvinen@linux.intel.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
Sort includes in n_tty alphabetically to make it easier to see if an
include is among the list or not.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20230309082035.14880-5-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
n_tty: Convert no_space_left to space_left boolean 2023-03-17T14:01:08+00:00 Ilpo Järvinen ilpo.jarvinen@linux.intel.com 2023-03-09T08:20:28+00:00 b8abba0eb1f5b8a05e864cf00f246e1c066775a2 The no_space_left variable is only assigned with 0 and 1. Change its type to boolean and move negation from its name into the check. Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> Link: https://lore.kernel.org/r/20230309082035.14880-2-ilpo.jarvinen@linux.intel.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
The no_space_left variable is only assigned with 0 and 1.

Change its type to boolean and move negation from its name into the
check.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20230309082035.14880-2-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
n_tty: Rename tail to old_tail in n_tty_read() 2022-11-22T16:51:34+00:00 Ilpo Järvinen ilpo.jarvinen@linux.intel.com 2022-11-11T14:25:02+00:00 947d66b68f3c4e7cf8f3f3500807b9d2a0de28ce The local tail variable in n_tty_read() is used for one purpose, it keeps the old tail. Thus, rename it appropriately to improve code readability. Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> Reviewed-by: Jiri Slaby <jirislaby@kernel.org> Link: https://lore.kernel.org/r/22b37499-ff9a-7fc1-f6e0-58411328d122@linux.intel.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
The local tail variable in n_tty_read() is used for one purpose, it
keeps the old tail. Thus, rename it appropriately to improve code
readability.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/22b37499-ff9a-7fc1-f6e0-58411328d122@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
tty: Make ldisc ->set_termios() old ktermios const 2022-08-30T12:22:34+00:00 Ilpo Järvinen ilpo.jarvinen@linux.intel.com 2022-08-16T11:57:36+00:00 8b7d2d95cf82f8ca034ac65d0f39a2b3359b680f There should be no reason to adjust old ktermios which is going to get discarded anyway. Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> Link: https://lore.kernel.org/r/20220816115739.10928-6-ilpo.jarvinen@linux.intel.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
There should be no reason to adjust old ktermios which is going to get
discarded anyway.

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220816115739.10928-6-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
tty: Use flow-control char function on closing path 2022-06-10T11:51:31+00:00 Ilpo Järvinen ilpo.jarvinen@linux.intel.com 2022-06-06T15:36:52+00:00 65534736d9a5cab5340ae8819e1394b6325e8390 Use n_tty_receive_char_flow_ctrl also on the closing path. This makes the code cleaner and consistent. However, there a small change of regression! The earlier closing path has a small difference compared with the normal receive path. If START_CHAR and STOP_CHAR are equal, their precedence is different depending on which path a character is processed. I don't know whether this difference was intentional or not, and if equal START_CHAR and STOP_CHAR is actually used anywhere. But it feels not so useful corner case. While this change would logically belong to those earlier changes, having a separate patch for this is useful. If this regresses, bisect can pinpoint this change rather than the large patch. Also, this change is not necessary to minimal fix for the issue addressed in the previous patch. Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> Link: https://lore.kernel.org/r/20220606153652.63554-3-ilpo.jarvinen@linux.intel.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
Use n_tty_receive_char_flow_ctrl also on the closing path. This makes
the code cleaner and consistent.

However, there a small change of regression!

The earlier closing path has a small difference compared with the
normal receive path. If START_CHAR and STOP_CHAR are equal, their
precedence is different depending on which path a character is
processed. I don't know whether this difference was intentional or
not, and if equal START_CHAR and STOP_CHAR is actually used anywhere.
But it feels not so useful corner case.

While this change would logically belong to those earlier changes,
having a separate patch for this is useful. If this regresses, bisect
can pinpoint this change rather than the large patch. Also, this
change is not necessary to minimal fix for the issue addressed in
the previous patch.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220606153652.63554-3-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
tty: Implement lookahead to process XON/XOFF timely 2022-06-10T11:51:31+00:00 Ilpo Järvinen ilpo.jarvinen@linux.intel.com 2022-06-06T15:36:51+00:00 6bb6fa6908ebd3cb4e14cd4f0ce272ec885d2eb0 When tty is not read from, XON/XOFF may get stuck into an intermediate buffer. As those characters are there to do software flow-control, it is not very useful. In the case where neither end reads from ttys, the receiving ends might not be able receive the XOFF characters and just keep sending more data to the opposite direction. This problem is almost guaranteed to occur with DMA which sends data in large chunks. If TTY is slow to process characters, that is, eats less than given amount in receive_buf, invoke lookahead for the rest of the chars to process potential XON/XOFF characters. We need to keep track of how many characters have been processed by the lookahead to avoid processing the flow control char again on the normal path. Bookkeeping occurs parallel on two layers (tty_buffer and n_tty) to avoid passing the lookahead_count through the whole call chain. When a flow-control char is processed, two things must occur: a) it must not be treated as normal char b) if not yet processed, flow-control actions need to be taken The return value of n_tty_receive_char_flow_ctrl() tells caller a), and b) is kept internal to n_tty_receive_char_flow_ctrl(). If characters were previous looked ahead, __receive_buf() makes two calls to the appropriate n_tty_receive_buf_* function. First call is made with lookahead_done=true for the characters that were subject to lookahead earlier and then with lookahead=false for the new characters. Either of the calls might be skipped when it has no characters to handle. Reported-by: Gilles Buloz <gilles.buloz@kontron.com> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> Link: https://lore.kernel.org/r/20220606153652.63554-2-ilpo.jarvinen@linux.intel.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
When tty is not read from, XON/XOFF may get stuck into an
intermediate buffer. As those characters are there to do software
flow-control, it is not very useful. In the case where neither end
reads from ttys, the receiving ends might not be able receive the
XOFF characters and just keep sending more data to the opposite
direction. This problem is almost guaranteed to occur with DMA
which sends data in large chunks.

If TTY is slow to process characters, that is, eats less than given
amount in receive_buf, invoke lookahead for the rest of the chars
to process potential XON/XOFF characters.

We need to keep track of how many characters have been processed by the
lookahead to avoid processing the flow control char again on the normal
path. Bookkeeping occurs parallel on two layers (tty_buffer and n_tty)
to avoid passing the lookahead_count through the whole call chain.

When a flow-control char is processed, two things must occur:
  a) it must not be treated as normal char
  b) if not yet processed, flow-control actions need to be taken
The return value of n_tty_receive_char_flow_ctrl() tells caller a), and
b) is kept internal to n_tty_receive_char_flow_ctrl().

If characters were previous looked ahead, __receive_buf() makes two
calls to the appropriate n_tty_receive_buf_* function. First call is
made with lookahead_done=true for the characters that were subject to
lookahead earlier and then with lookahead=false for the new characters.
Either of the calls might be skipped when it has no characters to
handle.

Reported-by: Gilles Buloz <gilles.buloz@kontron.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220606153652.63554-2-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
tty: Rework receive flow control char logic 2022-05-19T16:33:34+00:00 Ilpo Järvinen ilpo.jarvinen@linux.intel.com 2022-04-26T14:49:33+00:00 25e02ba60f0fbe65ba07553b5b2b8867726273c4 Add a helper to check if the character is a flow control one. This rework prepares for adding lookahead done check cleanly to n_tty_receive_char_flow_ctrl() between n_tty_is_char_flow_ctrl() and the actions taken on the flow control characters. No functional changes intended. Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> Link: https://lore.kernel.org/r/20220426144935.54893-2-ilpo.jarvinen@linux.intel.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
Add a helper to check if the character is a flow control one. This
rework prepares for adding lookahead done check cleanly to
n_tty_receive_char_flow_ctrl() between n_tty_is_char_flow_ctrl() and
the actions taken on the flow control characters.

No functional changes intended.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220426144935.54893-2-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>