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struct_usb_host_config(9) [centos man page]

STRUCT 
USB_HOST_CONF(9) Host-Side Data Types and Macro STRUCT USB_HOST_CONF(9) NAME
struct_usb_host_config - representation of a device's configuration SYNOPSIS
struct usb_host_config { struct usb_config_descriptor desc; char * string; struct usb_interface_assoc_descriptor * intf_assoc[USB_MAXIADS]; struct usb_interface * interface[USB_MAXINTERFACES]; struct usb_interface_cache * intf_cache[USB_MAXINTERFACES]; unsigned char * extra; int extralen; }; MEMBERS
desc the device's configuration descriptor. string pointer to the cached version of the iConfiguration string, if present for this configuration. intf_assoc[USB_MAXIADS] list of any interface association descriptors in this config interface[USB_MAXINTERFACES] array of pointers to usb_interface structures, one for each interface in the configuration. The number of interfaces is stored in desc.bNumInterfaces. These pointers are valid only while the the configuration is active. intf_cache[USB_MAXINTERFACES] array of pointers to usb_interface_cache structures, one for each interface in the configuration. These structures exist for the entire life of the device. extra pointer to buffer containing all extra descriptors associated with this configuration (those preceding the first interface descriptor). extralen length of the extra descriptors buffer. DESCRIPTION
USB devices may have multiple configurations, but only one can be active at any time. Each encapsulates a different operational environment; for example, a dual-speed device would have separate configurations for full-speed and high-speed operation. The number of configurations available is stored in the device descriptor as bNumConfigurations. A configuration can contain multiple interfaces. Each corresponds to a different function of the USB device, and all are available whenever the configuration is active. The USB standard says that interfaces are supposed to be numbered from 0 to desc.bNumInterfaces-1, but a lot of devices get this wrong. In addition, the interface array is not guaranteed to be sorted in numerical order. Use usb_ifnum_to_if to look up an interface entry based on its number. Device drivers should not attempt to activate configurations. The choice of which configuration to install is a policy decision based on such considerations as available power, functionality provided, and the user's desires (expressed through userspace tools). However, drivers can call usb_reset_configuration to reinitialize the current configuration and all its interfaces. COPYRIGHT
Kernel Hackers Manual 3.10 June 2014 STRUCT USB_HOST_CONF(9)

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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; int (* bind) (struct usb_configuration *); void (* unbind) (struct usb_configuration *); int (* setup) (struct usb_configuration *,const struct usb_ctrlrequest *); u8 bConfigurationValue; u8 iConfiguration; u8 bmAttributes; u8 bMaxPower; 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. bind Called from usb_add_config() to allocate resources unique to this configuration and to call usb_add_function() for each function used. 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. bMaxPower Copied into configuration descriptor. 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 independant 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 2.6. July 2010 STRUCT USB_CONFIGURA(9)
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