On Mon, May 10, 2021 at 09:00:54AM +0200, Jiri Slaby wrote:
> Many tty drivers contain code to compute bits count depending on termios
> cflags. So extract this code from serial core to a separate tty helper
> function called tty_get_byte_size.
>
> In the next patch, call to this new function will replace many copies of
> this code.
>
> [v2] simplified the code flow as suggested by Joe and Andy
>
> Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
> Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
> Cc: Joe Perches <joe@xxxxxxxxxxx>
> ---
> drivers/tty/serial/serial_core.c | 30 +++--------------------
> drivers/tty/tty_ioctl.c | 42 ++++++++++++++++++++++++++++++++
> include/linux/tty.h | 2 ++
> 3 files changed, 47 insertions(+), 27 deletions(-)
>
> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
> index d29329eb52f4..b3fc2b02a705 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -334,39 +334,15 @@ void
> uart_update_timeout(struct uart_port *port, unsigned int cflag,
> unsigned int baud)
> {
> - unsigned int bits;
> + unsigned int size;
>
> - /* byte size and parity */
> - switch (cflag & CSIZE) {
> - case CS5:
> - bits = 7;
> - break;
> - case CS6:
> - bits = 8;
> - break;
> - case CS7:
> - bits = 9;
> - break;
> - default:
> - bits = 10;
> - break; /* CS8 */
> - }
> -
> - if (cflag & CSTOPB)
> - bits++;
> - if (cflag & PARENB)
> - bits++;
> -
> - /*
> - * The total number of bits to be transmitted in the fifo.
> - */
> - bits = bits * port->fifosize;
> + size = tty_get_byte_size(cflag, true) * port->fifosize;
>
> /*
> * Figure the timeout to send the above number of bits.
> * Add .02 seconds of slop
> */
> - port->timeout = (HZ * bits) / baud + HZ/50;
> + port->timeout = (HZ * size) / baud + HZ/50;
> }
>
> EXPORT_SYMBOL(uart_update_timeout);
> diff --git a/drivers/tty/tty_ioctl.c b/drivers/tty/tty_ioctl.c
> index aa9ecc8be990..13acc3decd87 100644
> --- a/drivers/tty/tty_ioctl.c
> +++ b/drivers/tty/tty_ioctl.c
> @@ -300,6 +300,48 @@ int tty_termios_hw_change(const struct ktermios *a, const struct ktermios *b)
> }
> EXPORT_SYMBOL(tty_termios_hw_change);
>
> +/**
> + * tty_get_byte_size - get size of a byte
> + * @cflag: termios cflag value
> + * @account_flags: account for start and stop bits, second stop bit (if
> + * set), and parity (if set)
> + *
> + * Get the size of a byte in bits depending on @cflag. Depending on
> + * @account_flags parameter, the result also accounts start and stop bits,
> + * the second stop bit, and parity bit.
> + */
> +unsigned char tty_get_byte_size(unsigned int cflag, bool account_flags)
> +{
> + unsigned char bits;
> +
> + switch (cflag & CSIZE) {
> + case CS5:
> + bits = 5;
> + break;
> + case CS6:
> + bits = 6;
> + break;
> + case CS7:
> + bits = 7;
> + break;
> + case CS8:
> + default:
> + bits = 8;
> + break;
> + }
> +
> + if (!account_flags)
> + return bits;
> +
> + if (cflag & CSTOPB)
> + bits++;
> + if (cflag & PARENB)
> + bits++;
> +
> + return bits + 2;
> +}
> +EXPORT_SYMBOL_GPL(tty_get_byte_size);
This should really be two functions rather than passing a bool argument.
I think naming them
tty_get_word_size()
and
tty_get_frame_size()
would be much more clear than than "byte size" + flag.
I realise that the serial-driver interface only uses a cflag argument,
but I think we should consider passing a pointer to the termios
structure instead.
Johan
