USB_STRING_ID(9) Kernel Mode Gadget API USB_STRING_ID(9)NAME
usb_string_id - allocate an unused string ID
SYNOPSIS
int usb_string_id(struct usb_composite_dev * cdev);
ARGUMENTS
cdev
the device whose string descriptor IDs are being allocated
CONTEXT
single threaded during gadget setup
DESCRIPTION
usb_string_id() is called from bind callbacks to allocate string IDs. Drivers for functions, configurations, or gadgets will then store
that ID in the appropriate descriptors and string table.
All string identifier should be allocated using this, usb_string_ids_tab() or usb_string_ids_n() routine, to ensure that for example
different functions don't wrongly assign different meanings to the same identifier.
AUTHOR
David Brownell <dbrownell@users.sourceforge.net>
Author.
COPYRIGHT Kernel Hackers Manual 3.10 June 2014 USB_STRING_ID(9)
Check Out this Related Man Page
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)