From b81e201e405a5a274837e4a437bd72932cce56b4 Mon Sep 17 00:00:00 2001 From: Oliver Neukum Date: Thu, 7 Dec 2023 14:26:30 +0100 Subject: [PATCH] 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 Fixes: 9e98966c7bb94 ("tty: rework break handling") Link: https://lore.kernel.org/r/20231207132639.18250-1-oneukum@suse.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/tty_io.c | 3 +++ drivers/usb/class/cdc-acm.c | 3 +++ 2 files changed, 6 insertions(+) diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index 1c76e77e2..984e3098e 100755 --- 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 070b838c7..4e4a71307 100755 --- 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,