linux-kernel - [PATCH] USB :core :Prevent USB devices to autosuspend while setting interface

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Date:   Fri, 10 Nov 2017 21:32:07 +0530
From:   Abhijeet@...r.kernel.org, Kumar@...r.kernel.org
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jaejoong Kim <climbbb.kim@...il.com>,
        Jonathan Corbet <corbet@....net>,
        Abhijeet Kumar <abhijeet.kumar@...el.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] USB :core :Prevent USB devices to autosuspend while setting interface

From: Abhijeet Kumar <abhijeet.kumar@...el.com>

Runtime resume USB device in order to ensure that PM framework knows
that the we might be using the device in a short time and doesn't
autosuspend the device while we update it's interface. Without this
change, if device autosuspends and the kernel polling for block
devices is disabled through sysfs at runtime or through bootargs, then
storage devices might never unmount since the disconnect IRQ wont be
kicked at all.

Signed-off-by: Abhijeet Kumar <abhijeet.kumar@...el.com>
---
 drivers/usb/core/message.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
index 371a07d874a3..54a9accf88cb 100644
--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -1305,6 +1305,11 @@ int usb_set_interface(struct usb_device *dev, int interface, int alternate)
 	if (iface->unregistering)
 		return -ENODEV;
 
+	/*Letting runtime PM know that we wish to use the device in a
+	 * short time.
+	 */
+	pm_runtime_get(&iface->dev);
+
 	alt = usb_altnum_to_altsetting(iface, alternate);
 	if (!alt) {
 		dev_warn(&dev->dev, "selecting invalid altsetting %d\n",
-- 
1.9.1