On 06. 05. 21, 9:16, Joe Perches wrote:
On Wed, 2021-05-05 at 11:19 +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.
[]
diff --git a/drivers/tty/tty_ioctl.c b/drivers/tty/tty_ioctl.c
[]
+/**
+ * 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 = account_flags ? 2 : 0;
+
+ /* byte size and parity */
+ 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 && (cflag & CSTOPB))
+ bits++;
+
+ if (account_flags && (cflag & PARENB))
+ bits++;
+
+ return bits;
+}
+EXPORT_SYMBOL_GPL(tty_get_byte_size);
Perhaps clearer not testing account_flags multiple times.
Right. Originally, I had account_start_stop, account_stop, and
account_parity parameters. But they were either all false or all true.
So I unified them to account_flags, but the code remained overly complex.
unsigned char tty_get_byte_size(unsigned int cflag, bool account_flags)
{
unsigned char bits;
/* byte size and parity */
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) {
bits += 2; /* start/stop bits */
if (cflag & CSTOPB)
bits++;
if (cflag & PARENB)
bits++;
}
return bits;
}
thanks,
--
js
suse labs
