Hi,
On Mon, Jul 22, 2013 at 10:53:50AM -0400, Alan Stern wrote:
> On Mon, 22 Jul 2013, Felipe Balbi wrote:
>
> > indeed. Added a flush_work() call to usb_del_gadget_udc()
> >
> > > Also, what happens if two state transitions occur before the work queue
> > > gets around to executing the work routine?
> >
> > do we need to care about that at all ? It's a queue anyway, transitions
> > will still be notified in order.
>
> The "queue" in "workqueue" doesn't refer to the individual calls for a
> particular work_struct. If you call schedule_work(&gadget->work) twice
> in quick succession, the work routine is likely to get executed only
> once.
>
> I don't know if that would be a problem in this case -- the effect
> would be that some state transitions would appear to be skipped over.
> If nobody cares about anything but the current state, this would be
> okay.
I don't think anyone should care about the state transitions themselves,
only current state. Unless we want to have some tool which makes sure
device transitions through all states properly...
> > @@ -311,6 +320,7 @@ found:
> > kobject_uevent(&udc->dev.kobj, KOBJ_REMOVE);
> > device_unregister(&udc->dev);
> > device_unregister(&gadget->dev);
> > + flush_work(&gadget->work);
>
> Shouldn't the flush_work() call come before device_unregister()? You
> don't want to call sysfs_notify() on an unregistered device.
aaa, that's true. I was considering the possibility of someone adding a
usb_gadget_set_state() call on their ->release() method, but I guess
that would be a much bigger bug then the one I ended up causing :-)
Here's a newer version:
commit 766ed104b6f420dc7587a63dc1679f78176d082e
Author: Felipe Balbi <balbi@xxxxxx>
Date: Wed Jul 17 11:09:49 2013 +0300
usb: gadget: udc-core: move sysfs_notify() to a workqueue
usb_gadget_set_state() will call sysfs_notify()
which might sleep. Some users might want to call
usb_gadget_set_state() from the very IRQ handler
which actually changes the gadget state.
Instead of having every UDC driver add their own
workqueue for such a simple notification, we're
adding it generically to our struct usb_gadget,
so the details are hidden from all UDC drivers.
Signed-off-by: Felipe Balbi <balbi@xxxxxx>
diff --git a/drivers/usb/gadget/udc-core.c b/drivers/usb/gadget/udc-core.c
index ffd8fa5..eed8503 100644
--- a/drivers/usb/gadget/udc-core.c
+++ b/drivers/usb/gadget/udc-core.c
@@ -23,6 +23,7 @@
#include <linux/list.h>
#include <linux/err.h>
#include <linux/dma-mapping.h>
+#include <linux/workqueue.h>
#include <linux/usb/ch9.h>
#include <linux/usb/gadget.h>
@@ -101,11 +102,18 @@ EXPORT_SYMBOL_GPL(usb_gadget_unmap_request);
/* ------------------------------------------------------------------------- */
+static void usb_gadget_state_work(struct work_struct *work)
+{
+ struct usb_gadget *gadget = work_to_gadget(work);
+
+ sysfs_notify(&gadget->dev.kobj, NULL, "status");
+}
+
void usb_gadget_set_state(struct usb_gadget *gadget,
enum usb_device_state state)
{
gadget->state = state;
- sysfs_notify(&gadget->dev.kobj, NULL, "status");
+ schedule_work(&gadget->work);
}
EXPORT_SYMBOL_GPL(usb_gadget_set_state);
@@ -192,6 +200,7 @@ int usb_add_gadget_udc_release(struct device *parent, struct usb_gadget *gadget,
goto err1;
dev_set_name(&gadget->dev, "gadget");
+ INIT_WORK(&gadget->work, usb_gadget_state_work);
gadget->dev.parent = parent;
dma_set_coherent_mask(&gadget->dev, parent->coherent_dma_mask);
@@ -309,6 +318,7 @@ found:
usb_gadget_remove_driver(udc);
kobject_uevent(&udc->dev.kobj, KOBJ_REMOVE);
+ flush_work(&gadget->work);
device_unregister(&udc->dev);
device_unregister(&gadget->dev);
}
diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
index f1b0dca..942ef5e 100644
--- a/include/linux/usb/gadget.h
+++ b/include/linux/usb/gadget.h
@@ -22,6 +22,7 @@
#include <linux/slab.h>
#include <linux/scatterlist.h>
#include <linux/types.h>
+#include <linux/workqueue.h>
#include <linux/usb/ch9.h>
struct usb_ep;
@@ -475,6 +476,7 @@ struct usb_gadget_ops {
/**
* struct usb_gadget - represents a usb slave device
+ * @work: (internal use) Workqueue to be used for sysfs_notify()
* @ops: Function pointers used to access hardware-specific operations.
* @ep0: Endpoint zero, used when reading or writing responses to
* driver setup() requests
@@ -520,6 +522,7 @@ struct usb_gadget_ops {
* device is acting as a B-Peripheral (so is_a_peripheral is false).
*/
struct usb_gadget {
+ struct work_struct work;
/* readonly to gadget driver */
const struct usb_gadget_ops *ops;
struct usb_ep *ep0;
@@ -538,6 +541,7 @@ struct usb_gadget {
unsigned out_epnum;
unsigned in_epnum;
};
+#define work_to_gadget(w) (container_of((w), struct usb_gadget, work))
static inline void set_gadget_data(struct usb_gadget *gadget, void *data)
{ dev_set_drvdata(&gadget->dev, data); }
--
balbi
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