From 76f650f077f3edd7001c89da44eade2449e8f495 Mon Sep 17 00:00:00 2001 From: Mauro Carvalho Chehab Date: Wed, 5 Apr 2017 10:23:08 -0300 Subject: [PATCH] usb/hotplug.txt: convert to ReST and add to driver-api book This document describe some USB core features. Add it to the driver-api book. Signed-off-by: Mauro Carvalho Chehab Acked-by: Greg Kroah-Hartman Signed-off-by: Jonathan Corbet --- .../usb/hotplug.rst} | 68 ++++++++++--------- Documentation/driver-api/usb/index.rst | 1 + 2 files changed, 38 insertions(+), 31 deletions(-) rename Documentation/{usb/hotplug.txt => driver-api/usb/hotplug.rst} (76%) diff --git a/Documentation/usb/hotplug.txt b/Documentation/driver-api/usb/hotplug.rst similarity index 76% rename from Documentation/usb/hotplug.txt rename to Documentation/driver-api/usb/hotplug.rst index 5b243f315b2c..79663e653ca1 100644 --- a/Documentation/usb/hotplug.txt +++ b/Documentation/driver-api/usb/hotplug.rst @@ -1,4 +1,9 @@ -LINUX HOTPLUGGING +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 @@ -30,11 +35,11 @@ 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``) +========================================= -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 +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 @@ -51,26 +56,26 @@ Hotplug software and other resources is available at: Mailing list information is also available at that site. --------------------------------------------------------------------------- - +USB Policy Agent +================ -USB POLICY AGENT - -The USB subsystem currently invokes /sbin/hotplug when USB devices +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) +========== ============================================ +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 +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. @@ -79,19 +84,20 @@ 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 +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 +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 for full information about such table entries; or look +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. +macros such as these, and use driver_info to store more information:: USB_DEVICE (vendorId, productId) ... matching devices with specified vendor and product ids @@ -103,7 +109,7 @@ macros such as these, and use driver_info to store more information. ... 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: +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 }, @@ -116,10 +122,10 @@ and their quirks, might have a MODULE_DEVICE_TABLE like this: 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 usb_driver". +need such a struct :c:type:`usb_driver`. Drivers that connect directly to the USB subsystem should be declared -something like this: +something like this:: static struct usb_driver mydriver = { .name = "mydriver", @@ -138,11 +144,11 @@ something like this: 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. - - +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``. diff --git a/Documentation/driver-api/usb/index.rst b/Documentation/driver-api/usb/index.rst index 1e2a0c54eb3d..43f0a8b72b11 100644 --- a/Documentation/driver-api/usb/index.rst +++ b/Documentation/driver-api/usb/index.rst @@ -11,6 +11,7 @@ Linux USB API callbacks dma power-management + hotplug error-codes writing_usb_driver writing_musb_glue_layer -- 2.20.1