[Feature]add MT2731_MP2_MR2_SVN388 baseline version
Change-Id: Ief04314834b31e27effab435d3ca8ba33b499059
diff --git a/src/kernel/linux/v4.14/Documentation/driver-api/usb/hotplug.rst b/src/kernel/linux/v4.14/Documentation/driver-api/usb/hotplug.rst
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+USB hotplugging
+~~~~~~~~~~~~~~~
+
+Linux Hotplugging
+=================
+
+
+In hotpluggable busses like USB (and Cardbus PCI), end-users plug devices
+into the bus with power on. In most cases, users expect the devices to become
+immediately usable. That means the system must do many things, including:
+
+ - Find a driver that can handle the device. That may involve
+ loading a kernel module; newer drivers can use module-init-tools
+ to publish their device (and class) support to user utilities.
+
+ - Bind a driver to that device. Bus frameworks do that using a
+ device driver's probe() routine.
+
+ - Tell other subsystems to configure the new device. Print
+ queues may need to be enabled, networks brought up, disk
+ partitions mounted, and so on. In some cases these will
+ be driver-specific actions.
+
+This involves a mix of kernel mode and user mode actions. Making devices
+be immediately usable means that any user mode actions can't wait for an
+administrator to do them: the kernel must trigger them, either passively
+(triggering some monitoring daemon to invoke a helper program) or
+actively (calling such a user mode helper program directly).
+
+Those triggered actions must support a system's administrative policies;
+such programs are called "policy agents" here. Typically they involve
+shell scripts that dispatch to more familiar administration tools.
+
+Because some of those actions rely on information about drivers (metadata)
+that is currently available only when the drivers are dynamically linked,
+you get the best hotplugging when you configure a highly modular system.
+
+Kernel Hotplug Helper (``/sbin/hotplug``)
+=========================================
+
+There is a kernel parameter: ``/proc/sys/kernel/hotplug``, which normally
+holds the pathname ``/sbin/hotplug``. That parameter names a program
+which the kernel may invoke at various times.
+
+The /sbin/hotplug program can be invoked by any subsystem as part of its
+reaction to a configuration change, from a thread in that subsystem.
+Only one parameter is required: the name of a subsystem being notified of
+some kernel event. That name is used as the first key for further event
+dispatch; any other argument and environment parameters are specified by
+the subsystem making that invocation.
+
+Hotplug software and other resources is available at:
+
+ http://linux-hotplug.sourceforge.net
+
+Mailing list information is also available at that site.
+
+
+USB Policy Agent
+================
+
+The USB subsystem currently invokes ``/sbin/hotplug`` when USB devices
+are added or removed from system. The invocation is done by the kernel
+hub workqueue [hub_wq], or else as part of root hub initialization
+(done by init, modprobe, kapmd, etc). Its single command line parameter
+is the string "usb", and it passes these environment variables:
+
+========== ============================================
+ACTION ``add``, ``remove``
+PRODUCT USB vendor, product, and version codes (hex)
+TYPE device class codes (decimal)
+INTERFACE interface 0 class codes (decimal)
+========== ============================================
+
+If "usbdevfs" is configured, DEVICE and DEVFS are also passed. DEVICE is
+the pathname of the device, and is useful for devices with multiple and/or
+alternate interfaces that complicate driver selection. By design, USB
+hotplugging is independent of ``usbdevfs``: you can do most essential parts
+of USB device setup without using that filesystem, and without running a
+user mode daemon to detect changes in system configuration.
+
+Currently available policy agent implementations can load drivers for
+modules, and can invoke driver-specific setup scripts. The newest ones
+leverage USB module-init-tools support. Later agents might unload drivers.
+
+
+USB Modutils Support
+====================
+
+Current versions of module-init-tools will create a ``modules.usbmap`` file
+which contains the entries from each driver's ``MODULE_DEVICE_TABLE``. Such
+files can be used by various user mode policy agents to make sure all the
+right driver modules get loaded, either at boot time or later.
+
+See ``linux/usb.h`` for full information about such table entries; or look
+at existing drivers. Each table entry describes one or more criteria to
+be used when matching a driver to a device or class of devices. The
+specific criteria are identified by bits set in "match_flags", paired
+with field values. You can construct the criteria directly, or with
+macros such as these, and use driver_info to store more information::
+
+ USB_DEVICE (vendorId, productId)
+ ... matching devices with specified vendor and product ids
+ USB_DEVICE_VER (vendorId, productId, lo, hi)
+ ... like USB_DEVICE with lo <= productversion <= hi
+ USB_INTERFACE_INFO (class, subclass, protocol)
+ ... matching specified interface class info
+ USB_DEVICE_INFO (class, subclass, protocol)
+ ... matching specified device class info
+
+A short example, for a driver that supports several specific USB devices
+and their quirks, might have a MODULE_DEVICE_TABLE like this::
+
+ static const struct usb_device_id mydriver_id_table[] = {
+ { USB_DEVICE (0x9999, 0xaaaa), driver_info: QUIRK_X },
+ { USB_DEVICE (0xbbbb, 0x8888), driver_info: QUIRK_Y|QUIRK_Z },
+ ...
+ { } /* end with an all-zeroes entry */
+ };
+ MODULE_DEVICE_TABLE(usb, mydriver_id_table);
+
+Most USB device drivers should pass these tables to the USB subsystem as
+well as to the module management subsystem. Not all, though: some driver
+frameworks connect using interfaces layered over USB, and so they won't
+need such a struct :c:type:`usb_driver`.
+
+Drivers that connect directly to the USB subsystem should be declared
+something like this::
+
+ static struct usb_driver mydriver = {
+ .name = "mydriver",
+ .id_table = mydriver_id_table,
+ .probe = my_probe,
+ .disconnect = my_disconnect,
+
+ /*
+ if using the usb chardev framework:
+ .minor = MY_USB_MINOR_START,
+ .fops = my_file_ops,
+ if exposing any operations through usbdevfs:
+ .ioctl = my_ioctl,
+ */
+ };
+
+When the USB subsystem knows about a driver's device ID table, it's used when
+choosing drivers to probe(). The thread doing new device processing checks
+drivers' device ID entries from the ``MODULE_DEVICE_TABLE`` against interface
+and device descriptors for the device. It will only call ``probe()`` if there
+is a match, and the third argument to ``probe()`` will be the entry that
+matched.
+
+If you don't provide an ``id_table`` for your driver, then your driver may get
+probed for each new device; the third parameter to ``probe()`` will be
+``NULL``.