FTDI UARTs support only 7 or 8 data bits. Until now the ftdi_sio driver would
only report this limitation for CS6 to dmesg and fail to reflect this fact to
tcgetattr.
This patch reverts the unsupported CSIZE setting and reports the fact with less
severance to dmesg for both CS5 and CS6.
To test the patch it's sufficient to call
stty -F /dev/ttyUSB0 cs5
which will succeed without the patch and report an error with the patch
applied.
As an additional fix this patch ensures that the control request will always
include a data bit size, even in error cases.
Signed-off-by: Colin Leitner <colin.leitner@xxxxxxxxx>
---
drivers/usb/serial/ftdi_sio.c | 38 +++++++++++++++++++++++++-------------
1 file changed, 25 insertions(+), 13 deletions(-)
diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index b21d553..033d9b5 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -2115,6 +2115,17 @@ static void ftdi_set_termios(struct tty_struct *tty,
termios->c_cflag |= CRTSCTS;
}
+ /* All FTDI UART chips are limited to CS7/8. We won't pretend to
+ * support CS5/6 and revert the CSIZE setting instead. */
+ if ((C_CSIZE(tty) != CS8) && (C_CSIZE(tty) != CS7)) {
+ termios->c_cflag &= ~CSIZE;
+ if (old_termios)
+ termios->c_cflag |= old_termios->c_cflag & CSIZE;
+ else
+ termios->c_cflag |= CS8;
+ dev_warn(ddev, "requested CSIZE setting not supported\n");
+ }
+
cflag = termios->c_cflag;
if (!old_termios)
@@ -2151,19 +2162,20 @@ no_skip:
} else {
urb_value |= FTDI_SIO_SET_DATA_PARITY_NONE;
}
- if (cflag & CSIZE) {
- switch (cflag & CSIZE) {
- case CS7:
- urb_value |= 7;
- dev_dbg(ddev, "Setting CS7\n");
- break;
- case CS8:
- urb_value |= 8;
- dev_dbg(ddev, "Setting CS8\n");
- break;
- default:
- dev_err(ddev, "CSIZE was set but not CS7-CS8\n");
- }
+ switch (cflag & CSIZE) {
+ case CS7:
+ urb_value |= 7;
+ dev_dbg(ddev, "Setting CS7\n");
+ break;
+ case CS8:
+ urb_value |= 8;
+ dev_dbg(ddev, "Setting CS8\n");
+ break;
+ default:
+ /* It would actually be a driver bug if we ended up in here */
+ urb_value |= 8;
+ dev_err(ddev, "CSIZE was set but not CS7-CS8\n");
+ break;
}
/* This is needed by the break command since it uses the same command
--
1.7.10.4
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