Messages in this thread Patch in this message | | | Date | Thu, 13 Aug 2009 10:54:30 -0700 | From | David VomLehn <> | Subject | [PATCH] Combine two one-character CR-LF writes into one two-character write for O_ONLCR |
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When handling output of a newline character in O_ONLCR mode, the n_tty.c do_output_char() function uses the struct tty_operations function write_room() to determine whether it is possible to write two characters. It uses tty_put_char() for each character which, for the USB generic serial driver, translates into a write() for each character. For the USB generic serial driver the value returned by write_room() only applies to the next write(). A second write() done in quick succession will fail because the write URB buffer is still busy from the first write(). In this case, it results in the printing of a carriage return without the following line feed.
This patch combines the two write() calls into a single, two-character, write().
Signed-off-by: David VomLehn --- drivers/char/n_tty.c | 8 ++++---- 1 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c index 973be2f..bf06c61 100644 --- a/drivers/char/n_tty.c +++ b/drivers/char/n_tty.c @@ -297,12 +297,12 @@ static int do_output_char(unsigned char c, struct tty_struct *tty, int space) if (O_ONLRET(tty)) tty->column = 0; if (O_ONLCR(tty)) { - if (space < 2) + static const char crlf[] = {'\r', '\n'}; + if (space < ARRAY_SIZE(crlf)) return -1; tty->canon_column = tty->column = 0; - tty_put_char(tty, '\r'); - tty_put_char(tty, c); - return 2; + tty->ops->write(tty, crlf, ARRAY_SIZE(crlf)); + return ARRAY_SIZE(crlf); } tty->canon_column = tty->column; break;
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