This is a note to let you know that I've just added the patch titled
usb: cdc-acm: return correct error code on unsupported break
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
usb-cdc-acm-return-correct-error-code-on-unsupported.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit e0ca2dbe4246a72ed9191ea107075dc5955d7ac4
Author: Oliver Neukum <oneukum@xxxxxxxx>
Date: Thu Dec 7 14:26:30 2023 +0100
usb: cdc-acm: return correct error code on unsupported break
[ Upstream commit 66aad7d8d3ec5a3a8ec2023841bcec2ded5f65c9 ]
In ACM support for sending breaks to devices is optional.
If a device says that it doenot support sending breaks,
the host must respect that.
Given the number of optional features providing tty operations
for each combination is not practical and errors need to be
returned dynamically if unsupported features are requested.
In case a device does not support break, we want the tty layer
to treat that like it treats drivers that statically cannot
support sending a break. It ignores the inability and does nothing.
This patch uses EOPNOTSUPP to indicate that.
Signed-off-by: Oliver Neukum <oneukum@xxxxxxxx>
Fixes: 9e98966c7bb94 ("tty: rework break handling")
Link: https://lore.kernel.org/r/20231207132639.18250-1-oneukum@xxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 1c76e77e2d07..984e3098e631 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2480,6 +2480,9 @@ static int send_break(struct tty_struct *tty, unsigned int duration)
if (!retval) {
msleep_interruptible(duration);
retval = tty->ops->break_ctl(tty, 0);
+ } else if (retval == -EOPNOTSUPP) {
+ /* some drivers can tell only dynamically */
+ retval = 0;
}
tty_write_unlock(tty);
diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 070b838c7da9..4e4a71307d63 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -896,6 +896,9 @@ static int acm_tty_break_ctl(struct tty_struct *tty, int state)
struct acm *acm = tty->driver_data;
int retval;
+ if (!(acm->ctrl_caps & USB_CDC_CAP_BRK))
+ return -EOPNOTSUPP;
+
retval = acm_send_break(acm, state ? 0xffff : 0);
if (retval < 0)
dev_dbg(&acm->control->dev,
