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Subject[PATCH v2] 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@gmail.com>
---
V1 -> V2: changed :c:func:`usb_register` to usb_register()
changed the :c:func:`usb_deregister` to usb_deregister()
used literal blocks for makro module_usb_driver and added one more
stage of multi-stage macros.

.../driver-api/usb/writing_usb_driver.rst | 70 ++++++++++---------
1 file changed, 36 insertions(+), 34 deletions(-)

diff --git a/Documentation/driver-api/usb/writing_usb_driver.rst b/Documentation/driver-api/usb/writing_usb_driver.rst
index 2176297e5765..12e0481cceae 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 +84,35 @@ 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 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::
-
- static void __exit usb_skel_exit(void)
- {
- /* deregister this driver with the USB subsystem */
- usb_deregister(&skel_driver);
- }
- module_exit(usb_skel_exit);
+itself with the USB subsystem. This is done with usb_deregister()
+which is also hidden behind multi-stage macros.
+
+The init and exit functions are included in the macro module_usb_driver.
+Find the first three stages of macros below::
+
+ module_usb_driver(skel_driver);
+ |
+ V
+ module_driver(__usb_driver, usb_register, usb_deregister)
+ | \ \
+ V ---------- ----------
+ static int __init __driver##_init(void) \ | |
+ { \ v--------------------------- |
+ return __register(&(__driver) , ##__VA_ARGS__); \ |
+ } \ |
+ module_init(__driver##_init); \ |
+ static void __exit __driver##_exit(void) \ |
+ { \ v------------------------------------------------
+ __unregister(&(__driver) , ##__VA_ARGS__); \
+ } \
+ module_exit(__driver##_exit);


To enable the linux-hotplug system to load the driver automatically when
--
2.25.1
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