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    Subject[PATCH] Combine two one-character CR-LF writes into one two-character write for O_ONLCR
    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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