STRUCT USB_CONFIGURA(9)               Kernel Mode Gadget API              STRUCT USB_CONFIGURA(9)



NAME
       struct_usb_configuration - represents one gadget configuration

SYNOPSIS
       struct usb_configuration {
         const char * label;
         struct usb_gadget_strings ** strings;
         const struct usb_descriptor_header ** descriptors;
         void (* unbind) (struct usb_configuration *);
         int (* setup) (struct usb_configuration *,const struct usb_ctrlrequest *);
         u8 bConfigurationValue;
         u8 iConfiguration;
         u8 bmAttributes;
         u16 MaxPower;
         struct usb_composite_dev * cdev;
       };

MEMBERS
       label
           For diagnostics, describes the configuration.

       strings
           Tables of strings, keyed by identifiers assigned during bind() and by language IDs
           provided in control requests.

       descriptors
           Table of descriptors preceding all function descriptors. Examples include OTG and
           vendor-specific descriptors.

       unbind
           Reverses bind; called as a side effect of unregistering the driver which added this
           configuration.

       setup
           Used to delegate control requests that aren't handled by standard device
           infrastructure or directed at a specific interface.

       bConfigurationValue
           Copied into configuration descriptor.

       iConfiguration
           Copied into configuration descriptor.

       bmAttributes
           Copied into configuration descriptor.

       MaxPower
           Power consumtion in mA. Used to compute bMaxPower in the configuration descriptor
           after considering the bus speed.

       cdev
           assigned by usb_add_config() before calling bind(); this is the device associated with
           this configuration.

DESCRIPTION
       Configurations are building blocks for gadget drivers structured around function drivers.
       Simple USB gadgets require only one function and one configuration, and handle dual-speed
       hardware by always providing the same functionality. Slightly more complex gadgets may
       have more than one single-function configuration at a given speed; or have configurations
       that only work at one speed.

       Composite devices are, by definition, ones with configurations which include more than one
       function.

       The lifecycle of a usb_configuration includes allocation, initialization of the fields
       described above, and calling usb_add_config() to set up internal data and bind it to a
       specific device. The configuration's bind() method is then used to initialize all the
       functions and then call usb_add_function() for them.

       Those functions would normally be independent of each other, but that's not mandatory. CDC
       WMC devices are an example where functions often depend on other functions, with some
       functions subsidiary to others. Such interdependency may be managed in any way, so long as
       all of the descriptors complete by the time the composite driver returns from its bind
       routine.

AUTHOR
       David Brownell <dbrownell AT users.net>
           Author.

COPYRIGHT
Kernel Hackers Manual 4.8.                 January 2017                   STRUCT USB_CONFIGURA(9)