usb_gadget_config_buf(9) [centos man page]

USB_GADGET_CONFIG_BU(9) 				      Kernel Mode Gadget API					   USB_GADGET_CONFIG_BU(9)

NAME

       usb_gadget_config_buf - builts a complete configuration descriptor

SYNOPSIS

       int usb_gadget_config_buf(const struct usb_config_descriptor * config, void * buf, unsigned length,
				 const struct usb_descriptor_header ** desc);

ARGUMENTS

       config
	   Header for the descriptor, including characteristics such as power requirements and number of interfaces.

       buf
	   Buffer for the resulting configuration descriptor.

       length
	   Length of buffer. If this is not big enough to hold the entire configuration descriptor, an error code will be returned.

       desc
	   Null-terminated vector of pointers to the descriptors (interface, endpoint, etc) defining all functions in this device configuration.

DESCRIPTION

       This copies descriptors into the response buffer, building a descriptor for that configuration. It returns the buffer length or a negative
       status code. The config.wTotalLength field is set to match the length of the result, but other descriptor fields (including power usage and
       interface count) must be set by the caller.

       Gadget drivers could use this when constructing a config descriptor in response to USB_REQ_GET_DESCRIPTOR. They will need to patch the
       resulting bDescriptorType value if USB_DT_OTHER_SPEED_CONFIG is needed.

AUTHOR

       David Brownell <dbrownell@users.sourceforge.net>
	   Author.

COPYRIGHT

Kernel Hackers Manual 3.10					     June 2014						   USB_GADGET_CONFIG_BU(9)

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@users.sourceforge.net>
	   Author.

COPYRIGHT

Kernel Hackers Manual 3.10					     June 2014						   STRUCT USB_CONFIGURA(9)