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usb_match_id(9) - phpMan

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USB_MATCH_ID(9)                           USB Core APIs                           USB_MATCH_ID(9)



NAME
       usb_match_id - find first usb_device_id matching device or interface

SYNOPSIS
       const struct usb_device_id * usb_match_id(struct usb_interface * interface,
                                                 const struct usb_device_id * id);

ARGUMENTS
       interface
           the interface of interest

       id
           array of usb_device_id structures, terminated by zero entry

DESCRIPTION
       usb_match_id searches an array of usb_device_id's and returns the first one matching the
       device or interface, or null. This is used when binding (or rebinding) a driver to an
       interface. Most USB device drivers will use this indirectly, through the usb core, but
       some layered driver frameworks use it directly. These device tables are exported with
       MODULE_DEVICE_TABLE, through modutils, to support the driver loading functionality of USB
       hotplugging.

RETURN
       The first matching usb_device_id, or NULL.

       What Matches:

       The “match_flags” element in a usb_device_id controls which members are used. If the
       corresponding bit is set, the value in the device_id must match its corresponding member
       in the device or interface descriptor, or else the device_id does not match.

       “driver_info” is normally used only by device drivers, but you can create a wildcard
       “matches anything” usb_device_id as a driver's “modules.usbmap” entry if you provide an id
       with only a nonzero “driver_info” field. If you do this, the USB device driver's probe
       routine should use additional intelligence to decide whether to bind to the specified
       interface.

       What Makes Good usb_device_id Tables:

       The match algorithm is very simple, so that intelligence in driver selection must come
       from smart driver id records. Unless you have good reasons to use another selection
       policy, provide match elements only in related groups, and order match specifiers from
       specific to general. Use the macros provided for that purpose if you can.

       The most specific match specifiers use device descriptor data. These are commonly used
       with product-specific matches; the USB_DEVICE macro lets you provide vendor and product
       IDs, and you can also match against ranges of product revisions. These are widely used for
       devices with application or vendor specific bDeviceClass values.

       Matches based on device class/subclass/protocol specifications are slightly more general;
       use the USB_DEVICE_INFO macro, or its siblings. These are used with single-function
       devices where bDeviceClass doesn't specify that each interface has its own class.

       Matches based on interface class/subclass/protocol are the most general; they let drivers
       bind to any interface on a multiple-function device. Use the USB_INTERFACE_INFO macro, or
       its siblings, to match class-per-interface style devices (as recorded in bInterfaceClass).

       Note that an entry created by USB_INTERFACE_INFO won't match any interface if the device
       class is set to Vendor-Specific. This is deliberate; according to the USB spec the
       meanings of the interface class/subclass/protocol for these devices are also
       vendor-specific, and hence matching against a standard product class wouldn't work anyway.
       If you really want to use an interface-based match for such a device, create a match
       record that also specifies the vendor ID. (Unforunately there isn't a standard macro for
       creating records like this.)

       Within those groups, remember that not all combinations are meaningful. For example, don't
       give a product version range without vendor and product IDs; or specify a protocol without
       its associated class and subclass.

COPYRIGHT
Kernel Hackers Manual 4.8.                 January 2017                           USB_MATCH_ID(9)


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