| Message ID | 20210724212016.GA568154@pc (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | misc: powermate: update the reference count of the usb interface structure | expand |
Hi, On Sat, Jul 24, 2021 at 10:20:16PM +0100, Salah Triki wrote: > Use usb_get_intf() and usb_put_intf() in order to update the reference > count of the usb interface structure. This is quite pointless as the driver will be unbound from the interface before interface is deleted. > > Signed-off-by: Salah Triki <salah.triki@gmail.com> > --- > drivers/input/misc/powermate.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/input/misc/powermate.c b/drivers/input/misc/powermate.c > index c4e0e1886061..69dc3347478a 100644 > --- a/drivers/input/misc/powermate.c > +++ b/drivers/input/misc/powermate.c > @@ -337,7 +337,7 @@ static int powermate_probe(struct usb_interface *intf, const struct usb_device_i > goto fail3; > > pm->udev = udev; > - pm->intf = intf; > + pm->intf = usb_get_intf(intf); > pm->input = input_dev; > > usb_make_path(udev, pm->phys, sizeof(pm->phys)); > @@ -428,6 +428,7 @@ static void powermate_disconnect(struct usb_interface *intf) > usb_free_urb(pm->irq); > usb_free_urb(pm->config); > powermate_free_buffers(interface_to_usbdev(intf), pm); > + usb_put_intf(pm->intf); > > kfree(pm); > } > -- > 2.25.1 > Thanks.
Hi, On Sat, Jul 24, 2021 at 04:08:02PM -0700, Dmitry Torokhov wrote: > > On Sat, Jul 24, 2021 at 10:20:16PM +0100, Salah Triki wrote: > > Use usb_get_intf() and usb_put_intf() in order to update the reference > > count of the usb interface structure. > > This is quite pointless as the driver will be unbound from the interface > before interface is deleted. From the documentation of usb_get_intf(): [quote] Each live reference to a interface must be refcounted. Drivers for USB interfaces should normally record such references in their probe() methods, when they bind to an interface, and release them by calling usb_put_intf(), in their disconnect() methods. [/quote] Thanx
On Sun, Jul 25, 2021 at 12:56:37AM +0100, Salah Triki wrote: > Hi, > > On Sat, Jul 24, 2021 at 04:08:02PM -0700, Dmitry Torokhov wrote: > > > > On Sat, Jul 24, 2021 at 10:20:16PM +0100, Salah Triki wrote: > > > Use usb_get_intf() and usb_put_intf() in order to update the reference > > > count of the usb interface structure. > > > > This is quite pointless as the driver will be unbound from the interface > > before interface is deleted. > > From the documentation of usb_get_intf(): > > [quote] > > Each live reference to a interface must be refcounted. > > Drivers for USB interfaces should normally record such references in their > probe() methods, when they bind to an interface, and release them by calling > usb_put_intf(), in their disconnect() methods. > > [/quote] I see. In this case I recommend you submit a patch to the documentation clarifying this, as taking a reference when binding to an interface makes sense when dealing with a secondary interface, but not primary one. See for example drivers/usb/class/cdc-acm.c where it binds to the data interface, but also locates control interface and bumps up reference to that. As you may notice there is only a handful of drivers that use this API, and as I am looking at them most do not actually need to use it. Thanks.
diff --git a/drivers/input/misc/powermate.c b/drivers/input/misc/powermate.c index c4e0e1886061..69dc3347478a 100644 --- a/drivers/input/misc/powermate.c +++ b/drivers/input/misc/powermate.c @@ -337,7 +337,7 @@ static int powermate_probe(struct usb_interface *intf, const struct usb_device_i goto fail3; pm->udev = udev; - pm->intf = intf; + pm->intf = usb_get_intf(intf); pm->input = input_dev; usb_make_path(udev, pm->phys, sizeof(pm->phys)); @@ -428,6 +428,7 @@ static void powermate_disconnect(struct usb_interface *intf) usb_free_urb(pm->irq); usb_free_urb(pm->config); powermate_free_buffers(interface_to_usbdev(intf), pm); + usb_put_intf(pm->intf); kfree(pm); }
Use usb_get_intf() and usb_put_intf() in order to update the reference count of the usb interface structure. Signed-off-by: Salah Triki <salah.triki@gmail.com> --- drivers/input/misc/powermate.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)