TIOCSSERIAL is a horrid, underspecified, legacy interface which for most
serial devices is only useful for setting the close_delay and
closing_wait parameters.
The xmit_fifo_size parameter could be used to set the hardware transmit
fifo size of a legacy UART when it could not be detected, but the
interface is limited to eight bits and should be left unset when it is
not used.
Similarly, baud_base could be used to set the UART base clock when it
could not be detected, but might as well be left unset when it is not
known (which is the case for CDC).
Fix the cdc-acm TIOCGSERIAL implementation by dropping its custom
interpretation of the unused xmit_fifo_size and baud_base fields, which
overflowed the former with the URB buffer size and set the latter to the
current line speed. Also return the port line number, which is the only
other value used besides the close parameters.
Note that the current line speed can still be retrieved through the
standard termios interfaces.
Fixes: 18c75720e667 ("USB: allow users to run setserial with cdc-acm")
Signed-off-by: Johan Hovold <[email protected]>
---
drivers/usb/class/cdc-acm.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 43e31dad4831..b74713518b3a 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -929,8 +929,7 @@ static int get_serial_info(struct tty_struct *tty, struct serial_struct *ss)
{
struct acm *acm = tty->driver_data;
- ss->xmit_fifo_size = acm->writesize;
- ss->baud_base = le32_to_cpu(acm->line.dwDTERate);
+ ss->line = acm->minor;
ss->close_delay = jiffies_to_msecs(acm->port.close_delay) / 10;
ss->closing_wait = acm->port.closing_wait == ASYNC_CLOSING_WAIT_NONE ?
ASYNC_CLOSING_WAIT_NONE :
--
2.26.3
Am Donnerstag, den 08.04.2021, 15:16 +0200 schrieb Johan Hovold:
> TIOCSSERIAL is a horrid, underspecified, legacy interface which for most
> serial devices is only useful for setting the close_delay and
> closing_wait parameters.
>
> The xmit_fifo_size parameter could be used to set the hardware transmit
> fifo size of a legacy UART when it could not be detected, but the
> interface is limited to eight bits and should be left unset when it is
> not used.
>
> Similarly, baud_base could be used to set the UART base clock when it
> could not be detected, but might as well be left unset when it is not
> known (which is the case for CDC).
>
> Fix the cdc-acm TIOCGSERIAL implementation by dropping its custom
> interpretation of the unused xmit_fifo_size and baud_base fields, which
> overflowed the former with the URB buffer size and set the latter to the
> current line speed. Also return the port line number, which is the only
> other value used besides the close parameters.
>
> Note that the current line speed can still be retrieved through the
> standard termios interfaces.
>
> Fixes: 18c75720e667 ("USB: allow users to run setserial with cdc-acm")
> Signed-off-by: Johan Hovold <[email protected]>
Acked-by: Oliver Neukum <[email protected]>