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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)

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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 2.6. July 2010 STRUCT USB_HOST_CONF(9)
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