linux-kernel - [PATCH] Docs: usb: update struct usb_driver, __init and _

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Date:   Sun, 17 Oct 2021 23:49:48 +0200
From:   Philipp Hortmann <philipp.g.hortmann@...il.com>
To:     Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] Docs: usb: update struct usb_driver, __init and __exit

update struct usb_driver from usb-skeleton.c.
update __init and __exit functions that are moved from
usb-skeleton.c to common used multi-stage macros.

Signed-off-by: Philipp Hortmann <philipp.g.hortmann@...il.com>
---
 .../driver-api/usb/writing_usb_driver.rst     | 51 +++++++------------
 1 file changed, 19 insertions(+), 32 deletions(-)

diff --git a/Documentation/driver-api/usb/writing_usb_driver.rst b/Documentation/driver-api/usb/writing_usb_driver.rst
index 2176297e5765..1064adf79ccb 100644
--- a/Documentation/driver-api/usb/writing_usb_driver.rst
+++ b/Documentation/driver-api/usb/writing_usb_driver.rst
@@ -54,12 +54,15 @@ information is passed to the USB subsystem in the :c:type:`usb_driver`
 structure. The skeleton driver declares a :c:type:`usb_driver` as::
 
     static struct usb_driver skel_driver = {
-	    .name        = "skeleton",
-	    .probe       = skel_probe,
-	    .disconnect  = skel_disconnect,
-	    .fops        = &skel_fops,
-	    .minor       = USB_SKEL_MINOR_BASE,
-	    .id_table    = skel_table,
+           .name        = "skeleton",
+           .probe       = skel_probe,
+           .disconnect  = skel_disconnect,
+           .suspend     = skel_suspend,
+           .resume      = skel_resume,
+           .pre_reset   = skel_pre_reset,
+           .post_reset  = skel_post_reset,
+           .id_table    = skel_table,
+           .supports_autosuspend = 1,
     };
 
 
@@ -81,36 +84,20 @@ this user-space interaction. The skeleton driver needs this kind of
 interface, so it provides a minor starting number and a pointer to its
 :c:type:`file_operations` functions.
 
-The USB driver is then registered with a call to :c:func:`usb_register`,
-usually in the driver's init function, as shown here::
-
-    static int __init usb_skel_init(void)
-    {
-	    int result;
-
-	    /* register this driver with the USB subsystem */
-	    result = usb_register(&skel_driver);
-	    if (result < 0) {
-		    err("usb_register failed for the "__FILE__ "driver."
-			"Error number %d", result);
-		    return -1;
-	    }
-
-	    return 0;
-    }
-    module_init(usb_skel_init);
-
+The USB driver is then registered with a call to :c:func:`usb_register`
+which is usually in the driver's init function. Since this functionality
+is usable with many USB drivers, it is hidden behind multi-stage macros.
+While the first macros are USB specific the later macros are used in different
+subsystems. This removes a lot of boilerplate code.
 
 When the driver is unloaded from the system, it needs to deregister
 itself with the USB subsystem. This is done with the :c:func:`usb_deregister`
-function::
+which is also hidden behind multi-stage macros.
 
-    static void __exit usb_skel_exit(void)
-    {
-	    /* deregister this driver with the USB subsystem */
-	    usb_deregister(&skel_driver);
-    }
-    module_exit(usb_skel_exit);
+The init and exit functions are included in the macro :
+module_usb_driver(skel_driver);
+which is in the first stage replaced by:
+module_driver(__usb_driver, usb_register, usb_deregister)
 
 
 To enable the linux-hotplug system to load the driver automatically when
-- 
2.25.1