linux-kernel - [RFC PATCH] usb: core: correct usb_get

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Message-Id: <1477605750-30117-1-git-send-email-computersforpeace@gmail.com>
Date:   Thu, 27 Oct 2016 15:02:30 -0700
From:   Brian Norris <computersforpeace@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-usb@...r.kernel.org, <linux-kernel@...r.kernel.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Brian Norris <computersforpeace@...il.com>
Subject: [RFC PATCH] usb: core: correct usb_get_dev() documentation

In reading through a USB interface driver, I noticed that it called
usb_{get,put}_dev() in its probe() and disconnect() methods. This seemed
unnecessary, but a look at the comments here matched the usage.

USB interface devices seem to be well covered by the parent/child
relationship of the device model, and so it should be unnecessary for a
child device to grab a refcount on its parent device.

Signed-off-by: Brian Norris <computersforpeace@...il.com>
---
This reflects my understanding (and testing), as well as the majority of usage
-- there are *very* few interface drivers that actually call usb_get_dev(). If
I'm wrong, please feel free to tell me so! But I thought patching the
documentation would be the best way to solicit a response :)

 drivers/usb/core/usb.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index 592151461017..0ba7e070f04e 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -539,9 +539,9 @@ EXPORT_SYMBOL_GPL(usb_alloc_dev);
  *
  * Each live reference to a device should 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_dev(), in their disconnect() methods.
+ * The device driver core automatically handles this refcounting for USB
+ * interface drivers, but this API can be used for non-parent/child
+ * relationships.
  *
  * Return: A pointer to the device with the incremented reference counter.
  */
-- 
2.8.0.rc3.226.g39d4020