On 10. 05. 21, 11:47, Johan Hovold wrote:

quoted

--- 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)

...

quoted

+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.

Maybe I am screwed, but word means exactly 2B here. So instead, I would 
go for:
s/word/char/ -- might be confused with C's char, 1B, or maybe not -- or
s/word/data/ -- more generic and generally used in serial terminology.

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.

That's impossible as termios is not always at hand. Examples are:
pch_uart_startup -> uart_update_timeout
sunsab_console_setup -> sunsab_convert_to_sab -> uart_update_timeout
sunsu_kbd_ms_init -> sunsu_change_speed -> uart_update_timeout

Let me document that in the commit.

thanks,
-- 
js
suse labs