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

commit 8236800da115a3e24b9165c573067343f51cf5ea upstream.

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")
Signed-off-by: Krzysztof Opasiak <k.opasiak@samsung.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files 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);