Commit 2aa91851 authored by Jiri Slaby (SUSE)'s avatar Jiri Slaby (SUSE) Committed by Greg Kroah-Hartman
Browse files

tty: n_tty: extract ECHO_OP processing to a separate function 



__process_echoes() contains ECHO_OPs processing. It is stuffed in a
while loop and the whole function is barely readable. Separate it to a
new function: n_tty_process_echo_ops().

Signed-off-by: default avatar"Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20230827074147.2287-14-jirislaby@kernel.org


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e30364c7

drivers/tty/n_tty.c

+98 −96
Original line number Diff line number Diff line
@@ -582,139 +582,141 @@ static ssize_t process_output_block(struct tty_struct *tty, 
	return i;

}



/**

 * __process_echoes	-	write pending echo characters

 * @tty: terminal device

 *

 * Write previously buffered echo (and other ldisc-generated) characters to the

 * tty.

 *

 * Characters generated by the ldisc (including echoes) need to be buffered

 * because the driver's write buffer can fill during heavy program output.

 * Echoing straight to the driver will often fail under these conditions,

 * causing lost characters and resulting mismatches of ldisc state information.

 *

 * Since the ldisc state must represent the characters actually sent to the

 * driver at the time of the write, operations like certain changes in column

 * state are also saved in the buffer and executed here.

 *

 * A circular fifo buffer is used so that the most recent characters are

 * prioritized. Also, when control characters are echoed with a prefixed "^",

 * the pair is treated atomically and thus not separated.

 *

 * Locking: callers must hold %output_lock.

 */

static size_t __process_echoes(struct tty_struct *tty)

static int n_tty_process_echo_ops(struct tty_struct *tty, size_t *tail,

				  int space)

{

	struct n_tty_data *ldata = tty->disc_data;

	int	space, old_space;

	size_t tail;

	u8 c;



	old_space = space = tty_write_room(tty);



	tail = ldata->echo_tail;

	while (MASK(ldata->echo_commit) != MASK(tail)) {

		c = echo_buf(ldata, tail);

		if (c == ECHO_OP_START) {

	u8 op;

			bool space_left = true;



	/*

			 * Since add_echo_byte() is called without holding

			 * output_lock, we might see only portion of multi-byte

			 * operation.

	 * Since add_echo_byte() is called without holding output_lock, we

	 * might see only portion of multi-byte operation.

	 */

			if (MASK(ldata->echo_commit) == MASK(tail + 1))

				goto not_yet_stored;

	if (MASK(ldata->echo_commit) == MASK(*tail + 1))

		return -ENODATA;



	/*

			 * If the buffer byte is the start of a multi-byte

			 * operation, get the next byte, which is either the

			 * op code or a control character value.

	 * If the buffer byte is the start of a multi-byte operation, get the

	 * next byte, which is either the op code or a control character value.

	 */

			op = echo_buf(ldata, tail + 1);

	op = echo_buf(ldata, *tail + 1);



	switch (op) {

	case ECHO_OP_ERASE_TAB: {

		unsigned int num_chars, num_bs;



				if (MASK(ldata->echo_commit) == MASK(tail + 2))

					goto not_yet_stored;

				num_chars = echo_buf(ldata, tail + 2);

		if (MASK(ldata->echo_commit) == MASK(*tail + 2))

			return -ENODATA;



		num_chars = echo_buf(ldata, *tail + 2);



		/*

				 * Determine how many columns to go back

				 * in order to erase the tab.

				 * This depends on the number of columns

				 * used by other characters within the tab

				 * area.  If this (modulo 8) count is from

				 * the start of input rather than from a

				 * previous tab, we offset by canon column.

				 * Otherwise, tab spacing is normal.

		 * Determine how many columns to go back in order to erase the

		 * tab. This depends on the number of columns used by other

		 * characters within the tab area. If this (modulo 8) count is

		 * from the start of input rather than from a previous tab, we

		 * offset by canon column. Otherwise, tab spacing is normal.

		 */

		if (!(num_chars & 0x80))

			num_chars += ldata->canon_column;

		num_bs = 8 - (num_chars & 7);



				if (num_bs > space) {

					space_left = false;

					break;

				}

		if (num_bs > space)

			return -ENOSPC;



		space -= num_bs;

		while (num_bs--) {

			tty_put_char(tty, '\b');

			if (ldata->column > 0)

				ldata->column--;

		}

				tail += 3;

		*tail += 3;

		break;

	}

	case ECHO_OP_SET_CANON_COL:

		ldata->canon_column = ldata->column;

				tail += 2;

		*tail += 2;

		break;



	case ECHO_OP_MOVE_BACK_COL:

		if (ldata->column > 0)

			ldata->column--;

				tail += 2;

		*tail += 2;

		break;



	case ECHO_OP_START:

		/* This is an escaped echo op start code */

				if (!space) {

					space_left = false;

					break;

				}

		if (!space)

			return -ENOSPC;



		tty_put_char(tty, ECHO_OP_START);

		ldata->column++;

		space--;

				tail += 2;

		*tail += 2;

		break;



	default:

		/*

				 * If the op is not a special byte code,

				 * it is a ctrl char tagged to be echoed

				 * as "^X" (where X is the letter

				 * representing the control char).

				 * Note that we must ensure there is

				 * enough space for the whole ctrl pair.

				 *

		 * If the op is not a special byte code, it is a ctrl char

		 * tagged to be echoed as "^X" (where X is the letter

		 * representing the control char). Note that we must ensure

		 * there is enough space for the whole ctrl pair.

		 */

				if (space < 2) {

					space_left = false;

					break;

				}

		if (space < 2)

			return -ENOSPC;



		tty_put_char(tty, '^');

		tty_put_char(tty, op ^ 0100);

		ldata->column += 2;

		space -= 2;

				tail += 2;

		*tail += 2;

		break;

	}



	return space;

}



			if (!space_left)

/**

 * __process_echoes	-	write pending echo characters

 * @tty: terminal device

 *

 * Write previously buffered echo (and other ldisc-generated) characters to the

 * tty.

 *

 * Characters generated by the ldisc (including echoes) need to be buffered

 * because the driver's write buffer can fill during heavy program output.

 * Echoing straight to the driver will often fail under these conditions,

 * causing lost characters and resulting mismatches of ldisc state information.

 *

 * Since the ldisc state must represent the characters actually sent to the

 * driver at the time of the write, operations like certain changes in column

 * state are also saved in the buffer and executed here.

 *

 * A circular fifo buffer is used so that the most recent characters are

 * prioritized. Also, when control characters are echoed with a prefixed "^",

 * the pair is treated atomically and thus not separated.

 *

 * Locking: callers must hold %output_lock.

 */

static size_t __process_echoes(struct tty_struct *tty)

{

	struct n_tty_data *ldata = tty->disc_data;

	int	space, old_space;

	size_t tail;

	u8 c;



	old_space = space = tty_write_room(tty);



	tail = ldata->echo_tail;

	while (MASK(ldata->echo_commit) != MASK(tail)) {

		c = echo_buf(ldata, tail);

		if (c == ECHO_OP_START) {

			int ret = n_tty_process_echo_ops(tty, &tail, space);

			if (ret == -ENODATA)

				goto not_yet_stored;

			if (ret < 0)

				break;

			space = ret;

		} else {

			if (O_OPOST(tty)) {

				int retval = do_output_char(c, tty, space);