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Message-ID: <20230827074147.2287-14-jirislaby@kernel.org>
Date: Sun, 27 Aug 2023 09:41:46 +0200
From: "Jiri Slaby (SUSE)" <jirislaby@...nel.org>
To: gregkh@...uxfoundation.org
Cc: linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
"Jiri Slaby (SUSE)" <jirislaby@...nel.org>
Subject: [PATCH v2 13/14] 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: Jiri Slaby (SUSE) <jirislaby@...nel.org>
---
drivers/tty/n_tty.c | 194 ++++++++++++++++++++++----------------------
1 file changed, 98 insertions(+), 96 deletions(-)
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index bd6cd28f734f..edf59f6fc669 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -582,6 +582,100 @@ static ssize_t process_output_block(struct tty_struct *tty,
return i;
}
+static int n_tty_process_echo_ops(struct tty_struct *tty, size_t *tail,
+ int space)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+ u8 op;
+
+ /*
+ * 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))
+ 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.
+ */
+ 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))
+ 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.
+ */
+ if (!(num_chars & 0x80))
+ num_chars += ldata->canon_column;
+ num_bs = 8 - (num_chars & 7);
+
+ 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;
+ break;
+ }
+ case ECHO_OP_SET_CANON_COL:
+ ldata->canon_column = ldata->column;
+ *tail += 2;
+ break;
+
+ case ECHO_OP_MOVE_BACK_COL:
+ if (ldata->column > 0)
+ ldata->column--;
+ *tail += 2;
+ break;
+
+ case ECHO_OP_START:
+ /* This is an escaped echo op start code */
+ if (!space)
+ return -ENOSPC;
+
+ tty_put_char(tty, ECHO_OP_START);
+ ldata->column++;
+ space--;
+ *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 (space < 2)
+ return -ENOSPC;
+
+ tty_put_char(tty, '^');
+ tty_put_char(tty, op ^ 0100);
+ ldata->column += 2;
+ space -= 2;
+ *tail += 2;
+ break;
+ }
+
+ return space;
+}
+
/**
* __process_echoes - write pending echo characters
* @tty: terminal device
@@ -617,104 +711,12 @@ static size_t __process_echoes(struct tty_struct *tty)
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.
- */
- if (MASK(ldata->echo_commit) == MASK(tail + 1))
+ int ret = n_tty_process_echo_ops(tty, &tail, space);
+ if (ret == -ENODATA)
goto not_yet_stored;
- /*
- * 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);
-
- 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);
-
- /*
- * 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;
- }
- space -= num_bs;
- while (num_bs--) {
- tty_put_char(tty, '\b');
- if (ldata->column > 0)
- ldata->column--;
- }
- tail += 3;
- break;
- }
- case ECHO_OP_SET_CANON_COL:
- ldata->canon_column = ldata->column;
- tail += 2;
- break;
-
- case ECHO_OP_MOVE_BACK_COL:
- if (ldata->column > 0)
- ldata->column--;
- tail += 2;
- break;
-
- case ECHO_OP_START:
- /* This is an escaped echo op start code */
- if (!space) {
- space_left = false;
- break;
- }
- tty_put_char(tty, ECHO_OP_START);
- ldata->column++;
- space--;
- 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 (space < 2) {
- space_left = false;
- break;
- }
- tty_put_char(tty, '^');
- tty_put_char(tty, op ^ 0100);
- ldata->column += 2;
- space -= 2;
- tail += 2;
- }
-
- if (!space_left)
+ if (ret < 0)
break;
+ space = ret;
} else {
if (O_OPOST(tty)) {
int retval = do_output_char(c, tty, space);
--
2.42.0
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