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SubjectRe: [PATCH v7 4/4] usb: gadget: udc-core: independent registration of gadgets and gadget drivers
From
Date
Hello,

On 2015-11-23 16:32, Alan Stern wrote:
> On Mon, 23 Nov 2015, Marek Szyprowski wrote:
>
>> From: Ruslan Bilovol <ruslan.bilovol@gmail.com>
>>
>> Change behavior during registration of gadgets and
>> gadget drivers in udc-core. Instead of previous
>> approach when for successful probe of usb gadget driver
>> at least one usb gadget should be already registered
>> use another one where gadget drivers and gadgets
>> can be registered in udc-core independently.
>>
>> Independent registration of gadgets and gadget drivers
>> is useful for built-in into kernel gadget and gadget
>> driver case - because it's possible that gadget is
>> really probed only on late_init stage (due to deferred
>> probe) whereas gadget driver's probe is silently failed
>> on module_init stage due to no any UDC added.
>>
>> Also it is useful for modules case - now there is no
>> difference what module to insert first: gadget module
>> or gadget driver one.
>>
>> Tested-by: Maxime Ripard <maxime.ripard@free-electrons.com>
>> Signed-off-by: Ruslan Bilovol <ruslan.bilovol@gmail.com>
>> [simplified code as requested by Alan Stern and Felipe Balbi,
>> fixed checkpatch issues]
>> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
>> Tested-by: Peter Chen <peter.chen@freescale.com>
> I missed this the last time through...
>
>> @@ -403,6 +408,18 @@ int usb_add_gadget_udc_release(struct device *parent, struct usb_gadget *gadget,
>> usb_gadget_set_state(gadget, USB_STATE_NOTATTACHED);
>> 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)
>> + goto err4;
>> + list_del(&driver->pending);
> This has to be list_del_init(). And somewhere in
> usb_gadget_probe_driver() you need to do
> INIT_LIST_HEAD(&driver->pending).
>
>> @@ -577,6 +596,10 @@ int usb_gadget_unregister_driver(struct usb_gadget_driver *driver)
>> break;
>> }
>>
>> + if (ret) {
>> + list_del(&driver->pending);
> Otherwise this will cause a crash or corrupt some random area of
> memory.

'pending' handle is added to gadget_driver_pending_list in
usb_gadget_probe_driver(),
then when udc is available it is removed from this list and bound to the
given driver.
In usb_gadget_unregister_driver() the gadget is either unbound from the
udc or if is
was not bound to any udc, removed from pending list. I see no need for
adding
INIT_LIST_HEAD.

Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland



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