On Thu, Mar 25, 2021 at 10:41:09AM -0400, Alan Stern wrote:
> On Thu, Mar 25, 2021 at 03:29:21PM +0300, Heikki Krogerus wrote:
> > Introducing usb_for_each_port(). It works the same way as
> > usb_for_each_dev(), but instead of going through every USB
> > device in the system, it walks through the USB ports in the
> > system.
> >
> > Signed-off-by: Heikki Krogerus <heikki.kroge...@linux.intel.com>
>
> This has a couple of nasty errors.
>
> > ---
> > drivers/usb/core/usb.c | 43 ++++++++++++++++++++++++++++++++++++++++++
> > include/linux/usb.h | 1 +
> > 2 files changed, 44 insertions(+)
> >
> > diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
> > index 2ce3667ec6fae..6d49db9a1b208 100644
> > --- a/drivers/usb/core/usb.c
> > +++ b/drivers/usb/core/usb.c
> > @@ -398,6 +398,49 @@ int usb_for_each_dev(void *data, int (*fn)(struct
> > usb_device *, void *))
> > }
> > EXPORT_SYMBOL_GPL(usb_for_each_dev);
> >
> > +struct each_hub_arg {
> > + void *data;
> > + int (*fn)(struct device *, void *);
> > +};
> > +
> > +static int __each_hub(struct device *dev, void *data)
> > +{
> > + struct each_hub_arg *arg = (struct each_hub_arg *)data;
> > + struct usb_device *hdev = to_usb_device(dev);
>
> to_usb_device() won't work properly if the struct device isn't embedded
> in an actual usb_device structure. And that will happen, since the USB
> bus type holds usb_interface structures as well as usb_devices.
OK, so I need to filter them out.
> In fact, you should use usb_for_each_dev here; it already does what you
> want.
Unfortunately I can't use usb_for_each_dev here, because it deals with
struct usb_device while I need to deal with struct device in the
callback.
> > + struct usb_hub *hub;
> > + int ret;
> > + int i;
> > +
> > + hub = usb_hub_to_struct_hub(hdev);
> > + if (!hub)
> > + return 0;
> > +
> > + for (i = 0; i < hdev->maxchild; i++) {
> > + ret = arg->fn(&hub->ports[i]->dev, arg->data);
> > + if (ret)
> > + return ret;
> > + }
> > +
> > + return 0;
> > +}
>
> Don't you need some sort of locking or refcounting here? What would
> happen if this hub got removed while the routine was running?
I'll use a lock then.
thanks,
--
heikki
