[PATCH 4.9 103/153] usb: gadget: udc-core: Rescan pending list on driver unbind

Greg Kroah-Hartman
2017-03-10T09:24:56Z

From: Krzysztof Opasiak <k.opasiak@samsung.com>

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>

---
drivers/usb/gadget/udc/core.c | 45 ++++++++++++++++++++++++++++--------------
1 file changed, 31 insertions(+), 14 deletions(-)

--- 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 d
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 de
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 de
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
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);