patch "usb: gadget: udc-core: Rescan pending list on driver unbind" added to usb-next

patch "usb: gadget: udc-core: Rescan pending list on driver unbind" added to usb-next

[gregkh]

This is a note to let you know that I've just added the patch titled

    usb: gadget: udc-core: Rescan pending list on driver unbind

to my usb git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-next branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will also be merged in the next major kernel release
during the merge window.

If you have any questions about this process, please let me know.


>From 8236800da115a3e24b9165c573067343f51cf5ea Mon Sep 17 00:00:00 2001
From: Krzysztof Opasiak <k.opasiak@samsung.com>
Date: Mon, 16 Jan 2017 08:40:57 +0100
Subject: usb: gadget: udc-core: Rescan pending list on driver unbind

Since:

commit 855ed04a3758 ("usb: gadget: udc-core: independent registration
of gadgets and gadget drivers")

if we load gadget module but there is no free udc available
then it will be stored on a pending gadgets list.

$ modprobe g_zero.ko
$ modprobe g_ether.ko
[] udc-core: couldn't find an available UDC - added [g_ether] to list
of pending drivers

We scan this list each time when new UDC appears in system.
But we can get a free UDC each time after gadget unbind.
This commit add scanning of that list directly after unbinding
gadget from udc.

Thanks to this, when we unload first gadget:

$ rmmod g_zero.ko

gadget which is pending is automatically
attached to that UDC (if name matches).

Fixes: 855ed04a3758  ("usb: gadget: udc-core: independent registration of gadgets and gadget drivers")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Krzysztof Opasiak <k.opasiak@samsung.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
---
 drivers/usb/gadget/udc/core.c | 45 +++++++++++++++++++++++++++++--------------
 1 file changed, 31 insertions(+), 14 deletions(-)

diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
index 0402177f93cd..d685d82dcf48 100644
--- a/drivers/usb/gadget/udc/core.c
+++ b/drivers/usb/gadget/udc/core.c
@@ -1080,6 +1080,24 @@ static void usb_udc_nop_release(struct device *dev)
 	dev_vdbg(dev, "%s\n", __func__);
 }
 
+/* should be called with udc_lock held */
+static int check_pending_gadget_drivers(struct usb_udc *udc)
+{
+	struct usb_gadget_driver *driver;
+	int ret = 0;
+
+	list_for_each_entry(driver, &gadget_driver_pending_list, pending)
+		if (!driver->udc_name || strcmp(driver->udc_name,
+						dev_name(&udc->dev)) == 0) {
+			ret = udc_bind_to_driver(udc, driver);
+			if (ret != -EPROBE_DEFER)
+				list_del(&driver->pending);
+			break;
+		}
+
+	return ret;
+}
+
 /**
  * usb_add_gadget_udc_release - adds a new gadget to the udc class driver list
  * @parent: the parent device to this udc. Usually the controller driver's
@@ -1093,7 +1111,6 @@ int usb_add_gadget_udc_release(struct device *parent, struct usb_gadget *gadget,
 		void (*release)(struct device *dev))
 {
 	struct usb_udc		*udc;
-	struct usb_gadget_driver *driver;
 	int			ret = -ENOMEM;
 
 	udc = kzalloc(sizeof(*udc), GFP_KERNEL);
@@ -1136,17 +1153,9 @@ int usb_add_gadget_udc_release(struct device *parent, struct usb_gadget *gadget,
 	udc->vbus = true;
 
 	/* pick up one of pending gadget drivers */
-	list_for_each_entry(driver, &gadget_driver_pending_list, pending) {
-		if (!driver->udc_name || strcmp(driver->udc_name,
-						dev_name(&udc->dev)) == 0) {
-			ret = udc_bind_to_driver(udc, driver);
-			if (ret != -EPROBE_DEFER)
-				list_del(&driver->pending);
-			if (ret)
-				goto err5;
-			break;
-		}
-	}
+	ret = check_pending_gadget_drivers(udc);
+	if (ret)
+		goto err5;
 
 	mutex_unlock(&udc_lock);
 
@@ -1356,14 +1365,22 @@ int usb_gadget_unregister_driver(struct usb_gadget_driver *driver)
 		return -EINVAL;
 
 	mutex_lock(&udc_lock);
-	list_for_each_entry(udc, &udc_list, list)
+	list_for_each_entry(udc, &udc_list, list) {
 		if (udc->driver == driver) {
 			usb_gadget_remove_driver(udc);
 			usb_gadget_set_state(udc->gadget,
-					USB_STATE_NOTATTACHED);
+					     USB_STATE_NOTATTACHED);
+
+			/* Maybe there is someone waiting for this UDC? */
+			check_pending_gadget_drivers(udc);
+			/*
+			 * For now we ignore bind errors as probably it's
+			 * not a valid reason to fail other's gadget unbind
+			 */
 			ret = 0;
 			break;
 		}
+	}
 
 	if (ret) {
 		list_del(&driver->pending);
-- 
2.11.0