FAILED: patch "[PATCH] xhci: dbgtty: fix device unregister" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 1f73b8b56cf35de29a433aee7bfff26cea98be3f
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025120110-deuce-arrange-e66c@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 1f73b8b56cf35de29a433aee7bfff26cea98be3f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C5=81ukasz=20Bartosik?= <[email protected]>
Date: Wed, 19 Nov 2025 21:29:09 +0000
Subject: [PATCH] xhci: dbgtty: fix device unregister
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

When DbC is disconnected then xhci_dbc_tty_unregister_device() is called. However if there is any user space process blocked on write to DbC terminal device then it will never be signalled and thus stay blocked indifinitely.

This fix adds a tty_vhangup() call in xhci_dbc_tty_unregister_device(). The tty_vhangup() wakes up any blocked writers and causes subsequent write attempts to DbC terminal device to fail.

index b7f95565524d..57cdda4e09c8 100644
@@ -550,6 +550,12 @@ static void xhci_dbc_tty_unregister_device(struct xhci_dbc *dbc)
 
 	if (!port->registered)
 		return;
+	/*
+	 * Hang up the TTY. This wakes up any blocked
+	 * writers and causes subsequent writes to fail.
+	 */
+	tty_vhangup(port->port.tty);
+
 	tty_unregister_device(dbc_tty_driver, port->minor);
 	xhci_dbc_tty_exit_port(port);
 	port->registered = false;

From: Mathias Nyman <[email protected]>

[ Upstream commit e1ec140f273e1e30cea7e6d5f50934d877232121 ]

To support systems with several xhci controllers with active dbc on each xhci we need to use IDR to identify and give an index to each port.

Avoid using global struct tty_driver.driver_state for storing dbc port pointer as it won't work with several dbc ports

Stable-dep-of: 1f73b8b56cf3 ("xhci: dbgtty: fix device unregister")

---
 drivers/usb/host/xhci-dbgcap.h |  1 +
 drivers/usb/host/xhci-dbgtty.c | 46 ++++++++++++++++++++++++++++------
 2 files changed, 40 insertions(+), 7 deletions(-)

index 5109ea3c51da0..98e7331ca0951 100644
@@ -102,6 +102,7 @@ struct dbc_ep {
 struct dbc_port {
 	struct tty_port			port;
 	spinlock_t			port_lock;	/* port access */
+	int				minor;
 
 	struct list_head		read_pool;
 	struct list_head		read_queue;

2.51.0

From: Łukasz Bartosik <[email protected]>

[ Upstream commit 1f73b8b56cf35de29a433aee7bfff26cea98be3f ]

When DbC is disconnected then xhci_dbc_tty_unregister_device() is called. However if there is any user space process blocked on write to DbC terminal device then it will never be signalled and thus stay blocked indifinitely.

This fix adds a tty_vhangup() call in xhci_dbc_tty_unregister_device(). The tty_vhangup() wakes up any blocked writers and causes subsequent write attempts to DbC terminal device to fail.

---
 drivers/usb/host/xhci-dbgtty.c | 6 ++++++
 1 file changed, 6 insertions(+)

index 20e50e559c2a2..32f8c3d40fb0c 100644
@@ -489,6 +489,12 @@ static void xhci_dbc_tty_unregister_device(struct xhci_dbc *dbc)
 
 	if (!port->registered)
 		return;
+	/*
+	 * Hang up the TTY. This wakes up any blocked
+	 * writers and causes subsequent writes to fail.
+	 */
+	tty_vhangup(port->port.tty);
+
 	tty_unregister_device(dbc_tty_driver, port->minor);
 	xhci_dbc_tty_exit_port(port);
 	port->registered = false;

2.51.0