Documented "magic numbers" used in the CRTSCT flag code in terms of
register bit names from the chip specification.
Signed-off-by: Konstantin Shkolnyy <konstantin.shkolnyy@xxxxxxxxx>
---
drivers/usb/serial/cp210x.c | 38 ++++++++++++++++++++++++++++++++++----
1 file changed, 34 insertions(+), 4 deletions(-)
diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
index ede5c52..b2321a7 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -790,7 +790,7 @@ static void cp210x_get_termios_port(struct usb_serial_port *port,
cp210x_read_reg_block(port, CP210X_GET_FLOW, modem_ctl,
sizeof(modem_ctl));
- if (modem_ctl[0] & 0x08) {
+ if (modem_ctl[0] & 0x08) { /* if SERIAL_CTS_HANDSHAKE */
dev_dbg(dev, "%s - flow control = CRTSCTS\n", __func__);
cflag |= CRTSCTS;
} else {
@@ -952,17 +952,47 @@ static void cp210x_set_termios(struct tty_struct *tty,
__func__, modem_ctl[0], modem_ctl[4], modem_ctl[7]);
if (cflag & CRTSCTS) {
- modem_ctl[0] &= ~0x7B;
+ modem_ctl[0] &= ~0x7B; /* keep reserved D2 and D7 */
+ /*
+ * D1-D0 SERIAL_DTR_MASK =01b: DTR is held active
+ * D3 SERIAL_CTS_HANDSHAKE =1: CTS is a handshake line
+ * D4 SERIAL_DSR_HANDSHAKE =0
+ * D5 SERIAL_DCD_HANDSHAKE =0
+ * D6 SERIAL_DSR_SENSITIVITY =0
+ */
modem_ctl[0] |= 0x09;
+ /*
+ * D0 SERIAL_AUTO_TRANSMIT =0
+ * D1 SERIAL_AUTO_RECEIVE =0
+ * D2 SERIAL_ERROR_CHAR =0
+ * D3 SERIAL_NULL_STRIPPING =0
+ * D4 SERIAL_BREAK_CHAR =0
+ * D7-D6 SERIAL_RTS_MASK =10b: RTS for rcv flow control
+ */
modem_ctl[4] = 0x80;
dev_dbg(dev, "%s - flow control = CRTSCTS\n", __func__);
} else {
- modem_ctl[0] &= ~0x7B;
+ modem_ctl[0] &= ~0x7B; /* keep reserved D2 and D7 */
+ /*
+ * D1-D0 SERIAL_DTR_MASK = 01b: DTR is held active
+ * D3 SERIAL_CTS_HANDSHAKE = 0: CTS is a status input.
+ * D4 SERIAL_DSR_HANDSHAKE = 0
+ * D5 SERIAL_DCD_HANDSHAKE = 0
+ * D6 SERIAL_DSR_SENSITIVITY = 0
+ */
modem_ctl[0] |= 0x01;
+ /*
+ * D0 SERIAL_AUTO_TRANSMIT = 0
+ * D1 SERIAL_AUTO_RECEIVE = 0
+ * D2 SERIAL_ERROR_CHAR = 0
+ * D3 SERIAL_NULL_STRIPPING = 0
+ * D4 SERIAL_BREAK_CHAR = 0
+ * D7-D6 SERIAL_RTS_MASK =01b: RTS is statically active
+ */
modem_ctl[4] = 0x40;
dev_dbg(dev, "%s - flow control = NONE\n", __func__);
}
- modem_ctl[7] = 0;
+ modem_ctl[7] = 0; /* SERIAL_XOFF_CONTINUE = 0 */
dev_dbg(dev, "%s - write modem controls = %02x .. .. .. %02x .. .. %02x\n",
__func__, modem_ctl[0], modem_ctl[4], modem_ctl[7]);
--
1.8.4.5
--
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