USBDI(9) MidnightBSD Kernel Developer’s Manual USBDI(9)

NAME

usb_detach_wait, usb_detach_wakeup, usb_find_desc, usbd_abort_default_pipe, usbd_abort_pipe, usbd_alloc_buffer, usbd_alloc_xfer, usbd_bulk_transfer, usbd_clear_endpoint_stall, usbd_clear_endpoint_stall_async, usbd_clear_endpoint_toggle, usbd_close_pipe, usbd_device2interface_handle, usbd_devinfo, usbd_do_request, usbd_do_request_async, usbd_do_request_flags, usbd_do_request_flags_pipe, usbd_dopoll, usbd_endpoint_count, usbd_errstr, usbd_fill_deviceinfo, usbd_find_edesc, usbd_find_idesc, usbd_free_buffer, usbd_free_xfer, usbd_get_buffer, usbd_get_config, usbd_get_config_desc, usbd_get_config_desc_full, usbd_get_config_descriptor, usbd_get_device_descriptor, usbd_get_endpoint_descriptor, usbd_get_interface_altindex, usbd_get_interface_descriptor, usbd_get_no_alts, usbd_get_quirks, usbd_get_speed, usbd_get_string, usbd_get_string_desc, usbd_get_xfer_status, usbd_interface2device_handle, usbd_interface2endpoint_descriptor, usbd_interface_count, usbd_intr_transfer, usbd_open_pipe, usbd_open_pipe_intr, usbd_pipe2device_handle, usbd_ratecheck, usbd_set_config_index, usbd_set_config_no, usbd_set_interface, usbd_set_polling, usbd_setup_default_xfer, usbd_setup_isoc_xfer, usbd_setup_xfer, usbd_sync_transfer, usbd_transfer — Universal Serial Bus driver programming interface

SYNOPSIS

#include <dev/usb/usb.h>
#include <dev/usb/usbdi.h>
#include <dev/usb/usbdi_util.h>

void

usb_detach_wait(device_ptr_t dv);

void

usb_detach_wakeup(device_ptr_t dv);

const usb_descriptor_t *

usb_find_desc(usbd_device_handle dev, int type, int subtype);

usbd_status

usbd_abort_default_pipe(usbd_device_handle dev);

usbd_status

usbd_abort_pipe(usbd_pipe_handle pipe);

void *

usbd_alloc_buffer(usbd_xfer_handle xfer, u_int32_t size);

usbd_xfer_handle

usbd_alloc_xfer(usbd_device_handle dev);

usbd_status

usbd_bulk_transfer(usbd_xfer_handle xfer, usbd_pipe_handle pipe, u_int16_t flags, u_int32_t timeout, void *buf, u_int32_t *size, char *lbl);

usbd_status

usbd_clear_endpoint_stall(usbd_pipe_handle pipe);

usbd_status

usbd_clear_endpoint_stall_async(usbd_pipe_handle);

void

usbd_clear_endpoint_toggle(usbd_pipe_handle pipe);

usbd_status

usbd_close_pipe(usbd_pipe_handle pipe);

usbd_status

usbd_device2interface_handle(usbd_device_handle dev, u_int8_t ifaceno, usbd_interface_handle *iface);

void

usbd_devinfo(usbd_device_handle dev, int showclass, char *cp);

usbd_status

usbd_do_request(usbd_device_handle dev, usb_device_request_t *req, void *data);

usbd_status

usbd_do_request_async(usbd_device_handle dev, usb_device_request_t *req, void *data);

usbd_status

usbd_do_request_flags(usbd_device_handle dev, usb_device_request_t *req, void *data, u_int16_t flags, int *actlen, u_int32_t timo);

usbd_status

usbd_do_request_flags_pipe(usbd_device_handle dev, usbd_pipe_handle pipe, usb_device_request_t *req, void *data, u_int16_t flags, int *actlen, u_int32_t timeout);

void

usbd_dopoll(usbd_interface_handle iface);

usbd_status

usbd_endpoint_count(usbd_interface_handle iface, u_int8_t *count);

const char *

usbd_errstr(usbd_status err);

void

usbd_fill_deviceinfo(usbd_device_handle dev, struct usb_device_info *di, int usedev);

usb_endpoint_descriptor_t *

usbd_find_edesc(usb_config_descriptor_t *cd, int ifaceidx, int altidx, int endptidx);

usb_interface_descriptor_t *

usbd_find_idesc(usb_config_descriptor_t *cd, int ifaceidx, int altidx);

void

usbd_free_buffer(usbd_xfer_handle xfer);

usbd_status

usbd_free_xfer(usbd_xfer_handle xfer);

void *

usbd_get_buffer(usbd_xfer_handle xfer);

usbd_status

usbd_get_config(usbd_device_handle dev, u_int8_t *conf);

usbd_status

usbd_get_config_desc(usbd_device_handle dev, int confidx, usb_config_descriptor_t *d);

usbd_status

usbd_get_config_desc_full(usbd_device_handle dev, int conf, void *d, int size);

usb_config_descriptor_t *

usbd_get_config_descriptor(usbd_device_handle dev);

usb_device_descriptor_t *

usbd_get_device_descriptor(usbd_device_handle dev);

usb_endpoint_descriptor_t *

usbd_get_endpoint_descriptor(usbd_interface_handle iface, u_int8_t address);

int

usbd_get_interface_altindex(usbd_interface_handle iface);

usb_interface_descriptor_t *

usbd_get_interface_descriptor(usbd_interface_handle iface);

int

usbd_get_no_alts(usb_config_descriptor_t *cdesc, int ifaceno);

const struct usbd_quirks *

usbd_get_quirks(usbd_device_handle dev);

int

usbd_get_speed(usbd_device_handle dev);

usbd_status

usbd_get_string(usbd_device_handle dev, int si, char *buf);

usbd_status

usbd_get_string_desc(usbd_device_handle dev, int sindex, int langid, usb_string_descriptor_t *sdesc, int *sizep);

void

usbd_get_xfer_status(usbd_xfer_handle xfer, usbd_private_handle *priv, void **buffer, u_int32_t *count, usbd_status *status);

void

usbd_interface2device_handle(usbd_interface_handle iface, usbd_device_handle *dev);

usb_endpoint_descriptor_t *

usbd_interface2endpoint_descriptor(usbd_interface_handle iface, u_int8_t index);

usbd_status

usbd_interface_count(usbd_device_handle dev, u_int8_t *count);

usbd_status

usbd_intr_transfer(usbd_xfer_handle xfer, usbd_pipe_handle pipe, u_int16_t flags, u_int32_t timeout, void *buf, u_int32_t *size, char *lbl);

usbd_status

usbd_open_pipe(usbd_interface_handle iface, u_int8_t address, u_int8_t flags, usbd_pipe_handle *pipe);

usbd_status

usbd_open_pipe_intr(usbd_interface_handle iface, u_int8_t address, u_int8_t flags, usbd_pipe_handle *pipe, usbd_private_handle priv, void *buffer, u_int32_t len, usbd_callback cb, int ival);

usbd_device_handle

usbd_pipe2device_handle(usbd_pipe_handle pipe);

int

usbd_ratecheck(struct timeval *last);

usbd_status

usbd_set_config_index(usbd_device_handle dev, int index, int msg);

usbd_status

usbd_set_config_no(usbd_device_handle dev, int no, int msg);

usbd_status

usbd_set_interface(usbd_interface_handle iface, int altidx);

void

usbd_set_polling(usbd_device_handle dev, int on);

void

usbd_setup_default_xfer(usbd_xfer_handle xfer, usbd_device_handle dev, usbd_private_handle priv, u_int32_t timeout, usb_device_request_t *req, void *buffer, u_int32_t length, u_int16_t flags, usbd_callback callback);

void

usbd_setup_isoc_xfer(usbd_xfer_handle xfer, usbd_pipe_handle pipe, usbd_private_handle priv, u_int16_t *frlengths, u_int32_t nframes, u_int16_t flags, usbd_callback callback);

void

usbd_setup_xfer(usbd_xfer_handle xfer, usbd_pipe_handle pipe, usbd_private_handle priv, void *buffer, u_int32_t length, u_int16_t flags, u_int32_t timeout, usbd_callback callback);

usbd_status

usbd_sync_transfer(usbd_xfer_handle xfer);

usbd_status

usbd_transfer(usbd_xfer_handle xfer);

DESCRIPTION

The Universal Serial Bus (USB) driver programming interface provides USB peripheral drivers with a host controller independent API for controlling and communicating with USB peripherals.

Typically, drivers will first use some combination of the functions usbd_set_config_no(), usbd_get_config_descriptor(), usbd_set_interface(), usbd_get_interface_descriptor(), usbd_device2interface_handle(), usbd_endpoint_count() and usbd_interface2endpoint_descriptor() to query the device’s properties and prepare it for use. Drivers can then perform requests on the USB control pipe using usbd_do_request(), they can open pipes using the functions usbd_open_pipe() and usbd_open_pipe_intr(), and perform transfers over these pipes using usbd_alloc_xfer(), usbd_setup_xfer() and usbd_transfer(). Finally, the functions usbd_abort_pipe(), usbd_close_pipe() and usbd_free_xfer() are used to cancel outstanding transfers, close open pipes and deallocate transfer structures.

The usbd_get_device_descriptor() function returns a pointer to the USB device descriptor for dev. See USB Descriptors below for information about the USB device descriptor.

The usbd_get_config_desc() function retrieves the specified configuration descriptor from the device. The confidx parameter specifies the configuration descriptor index, which must be less than the bNumConfigurations value in the device descriptor. The function usbd_get_config_desc_full() retrieves a full configuration descriptor, which has all related interface and endpoint descriptors appended to a normal configuration descriptor. The parameter d should point to memory that is at least size bytes in length, and this should be at least as long as the wTotalLength value from the configuration descriptor. See USB Descriptors below for information about the USB configuration descriptor.

The usbd_get_config() function retrieves the current configuration number from the device, i.e. the bConfigurationValue value from the configuration that is active. If the device is unconfigured then USB_UNCONFIG_NO is returned. The current configuration can be changed by calling either usbd_set_config_index() or usbd_set_config_no(). The difference between these functions is that usbd_set_config_index() accepts a configuration index number that is less than the bNumConfigurations value from the device descriptor, whereas usbd_set_config_no() requires the bConfigurationValue value of the desired configuration to be provided instead. To unconfigure the device, supply a configuration index of USB_UNCONFIG_INDEX to usbd_set_config_index(), or else specify a configuration number of USB_UNCONFIG_NO to usbd_set_config_no().

The usbd_get_config_descriptor() function returns a pointer to an in-memory copy of the full configuration descriptor of the configuration that is currently active. The returned pointer remains valid until the device configuration is changed using usbd_set_config_index() or usbd_set_config_no(). If the device is unconfigured then NULL is returned instead.

The function usbd_interface_count() returns the number of interfaces available in the current device configuration. The usbd_get_no_alts() function determines the number of alternate interfaces in a full configuration descriptor by counting the interface descriptors with bInterfaceNumber equal to ifaceno (the count includes alternate index zero). The usbd_find_idesc() function locates an interface descriptor within a full configuration descriptor. The ifaceidx parameter specifies the interface index number, which should be less than the number of interfaces in the configuration descriptor (i.e. the value returned by usbd_interface_count() or the bNumInterface field from the configuration descriptor). An alternate interface can be specified using a non-zero altidx, which should be less than the value returned by usbd_get_no_alts(). The return value is a pointer to the requested interface descriptor within the full configuration descriptor, or NULL if the specified interface descriptor does not exist. Note that the altidx parameter specifies the alternate setting by index number starting at zero; it is not the alternate setting number defined in the interface descriptor.

The function usbd_find_edesc() locates an endpoint descriptor within a full configuration descriptor. The ifaceidx and altidx parameters are the same as described for usbd_find_idesc(), and the endptidx parameter is an endpoint index number that should be less than the bNumEndpoints field in the interface descriptor. The return value is a pointer to the requested endpoint descriptor within the full configuration descriptor, or NULL if the specified endpoint descriptor does not exist. Note that the altidx and endptidx parameters are index numbers starting at zero; they are not the alternate setting and endpoint address defined in the descriptors.

The usbd_get_speed() function returns the device speed. This can be USB_SPEED_LOW, USB_SPEED_FULL or USB_SPEED_HIGH.

USB devices optionally support string descriptors, which can be retrieved using the usbd_get_string() or usbd_get_string_desc() functions. Device, configuration and interface descriptors reference strings by an index number that can be supplied to these functions. The usbd_get_string() function should be used unless a non-default language is required. It requires that buf points to a buffer of at least USB_MAX_STRING_LEN bytes in size. The si parameter specified which string to retrieve.

The usb_find_desc() function searches through the in-memory full configuration descriptor for the active configuration and finds the first descriptor that has a bDescriptorType equal to type, and if subtype is not equal to USBD_SUBTYPE_ANY, the descriptor must also have a bDescriptorSubtype equal to subtype. If found, then a pointer to the descriptor is returned. Otherwise, usb_find_desc() returns NULL. The returned pointer is valid until the device configuration is changed using usbd_set_config_index() or usbd_set_config_no().

The USB driver interface uses opaque interface handles to refer to configuration interfaces. These handles remain valid until the device configuration is changed using usbd_set_config_index() or usbd_set_config_no(). The usbd_device2interface_handle() function retrieves an interface handle. The ifaceno parameter is an interface index number starting at zero. If the device is configured and the specified interface exists, then USBD_NORMAL_COMPLETION is returned and the interface handle is stored in *iface. Otherwise an error code is returned and *iface is not changed. The usbd_interface2device_handle() function retrieves the device handle from an interface handle. This is just for convenience to save passing around the device handle as well as the interface handle. The usbd_set_interface() function changes the alternate setting number for an interface to the alternate setting identified by the zero-based index number altidx. This operation invalidates any existing endpoints on this interface and their descriptors. The usbd_get_interface_altindex() function returns the current alternative setting index as was specified when calling usbd_set_interface(). The usbd_endpoint_count() function retrieves the number of endpoints associated with the specified interface. The usbd_interface2endpoint_descriptor() function returns a pointer to an in-memory endpoint descriptor for the endpoint that has an index number of index. This pointer remains valid until the configuration or alternate setting number are changed. The function usbd_get_endpoint_descriptor() is like usbd_interface2endpoint_descriptor() but it accepts a bEndpointAddress address value instead of an index.

The usbd_fill_deviceinfo() function fills out a usb_device_info structure with information about the device. The vendor and product names come from the device itself, falling back to a table lookup or just providing the IDs in hexadecimal. If usedev is zero then usbd_fill_deviceinfo() will not attempt to retrieve the vendor and product names from the device. The usb_device_info structure is defined in <dev/usb/usb.h> as follows:

struct usb_device_info {

u_int8_t

udi_bus;

u_int8_t

udi_addr;

/* device address */

usb_event_cookie_t udi_cookie;

char

udi_product[USB_MAX_STRING_LEN];

char

udi_vendor[USB_MAX_STRING_LEN];

char

udi_release[8];

u_int16_t

udi_productNo;

u_int16_t

udi_vendorNo;

u_int16_t

udi_releaseNo;

u_int8_t

udi_class;

u_int8_t

udi_subclass;

u_int8_t

udi_protocol;

u_int8_t

udi_config;

u_int8_t

udi_speed;

#define USB_SPEED_LOW 1
#define USB_SPEED_FULL 2
#define USB_SPEED_HIGH 3

int

udi_power;

/* power consumption in mA */

int

udi_nports;

char

udi_devnames[USB_MAX_DEVNAMES][USB_MAX_DEVNAMELEN];

/* hub only: addresses of devices on ports */

u_int8_t

udi_ports[16];

#define USB_PORT_ENABLED 0xff
#define USB_PORT_SUSPENDED 0xfe
#define USB_PORT_POWERED 0xfd
}

The usbd_devinfo() function generates a string description of the USB device. The cp argument should point to a 1024-byte buffer (XXX the maximum length is approximately 320 chars, but there is no sanity checking and everything uses 1024-character buffers). Device class information is included if the showclass parameter is non-zero.

The usbd_get_quirks() function returns information from a table of devices that require special workarounds in order to function correctly. The returned structure is defined in <dev/usb/usb_quirks.h> as follows:

struct usbd_quirks {

u_int32_t uq_flags;

/* Device problems */

};

See <dev/usb/usb_quirks.h> for a list of all currently defined quirks.

USB control requests are performed via usb_device_request_t structures, defined in <dev/usb/usb.h> as follows:

typedef struct {

uByte

bmRequestType;

uByte

bRequest;

uWord

wValue;

uWord

wIndex;

uWord

wLength;

} UPACKED usb_device_request_t;

The usbd_do_request() function performs a single request synchronously. The req parameter should point to a properly initialized usb_device_request_t, and when the wLength field is non-zero, data should point at a buffer that is at least wLength bytes in length. The request timeout is set to 5 seconds, so the operation will fail with USBD_TIMEOUT if the device does not respond within that time. The usbd_do_request_async() function is like usbd_do_request(), but it does not wait for the request to complete before returning. This routine does not block so it can be used from contexts where sleeping is not allowed. Note that there is no notification mechanism to report when the operation completed nor is there a way to determine whether the request succeeded, so this function is of limited use. See usbd_setup_default_xfer() and usbd_transfer() for a way to invoke an asynchronous callback upon completion of a control request. The usbd_do_request_flags() function is like usbd_do_request(), but additional flags can be specified, the timeout is configurable, and the actual number of bytes transferred is made available to the caller. The usbd_do_request_flags_pipe() function uses a specified pipe instead of the default pipe.

The function usbd_open_pipe() creates a pipe connected to a specified endpoint on a specified interface. The parameter address should be the bEndpointAddress value from one of this interface’s endpoint descriptors. If flags contains USBD_EXCLUSIVE_USE then the operation will only succeed if there are no open pipes already connected to the specified endpoint. The usbd_open_pipe_intr() function creates an interrupt pipe connected to the specified endpoint. The parameter address should be the bEndpointAddress value from one of this interface’s endpoint descriptors. The flags parameter is passed to usbd_setup_xfer(). The buffer and len parameters define a buffer that is to be used for the interrupt transfers. The callback to be invoked each time a transfer completes is specified by cb, and priv is an argument to be passed to the callback function. The ival parameter specifies the maximum acceptable interval between transfers; in practice the transfers may occur more frequently. The function usbd_pipe2device_handle() returns the device associated with the specified pipe.

The usbd_abort_pipe() function aborts all active or waiting transfers on the specified pipe. Each transfer is aborted with a USBD_CANCELLED status; callback routines must detect this error code to ensure that they do not attempt to initiate a new transfer in response to one being aborted. This routine blocks while it is waiting for the hardware to complete processing of aborted transfers, so it is only safe to call it in contexts where sleeping is allowed. The function usbd_abort_default_pipe() aborts all active or waiting transfers on the default pipe. Like usbd_abort_pipe(), it blocks waiting for the hardware processing to complete.

When a pipe has no active or waiting transfers, the pipe may be closed using the usbd_close_pipe() function. Once a pipe is closed, its pipe handle becomes invalid and may no longer be used.

USB transfer handles are allocated using the function usbd_alloc_xfer() and may be freed using usbd_free_xfer().

The function usbd_setup_xfer() initializes a transfer handle with the details of a transfer to or from a USB device. The xfer parameter specifies the transfer handle to initialize, pipe specifies the pipe on which the transfer is to take place, and priv is an argument that will be passed to callback function. The arguments buffer and length define the data buffer for the transfer. If length is zero then the buffer may be NULL. The flags parameter may contain the following flags:

USBD_NO_COPY

This is used in association with usbd_alloc_buffer() and usbd_free_buffer() to use a dedicated DMA-capable buffer for the transfer.

USBD_SYNCHRONOUS

Wait for the transfer to compete in usbd_transfer().

USBD_SHORT_XFER_OK

Permit transfers shorter than the requested data length.

USBD_FORCE_SHORT_XFER

Force a short transfer at the end of a write operation to let the device know that the transfer has ended.

The timeout parameter specifies a timeout for the transfer in milliseconds. A value of USBD_NO_TIMEOUT indicates that no timeout should be configured. The parameter callback specifies the function to call when the transfer completes. Note that usbd_setup_xfer() does not actually initiate the transfer. The usbd_setup_default_xfer() initializes a control transfer for the default pipe. The req parameter should point at a completed usb_device_request_t structure. The function usbd_setup_isoc_xfer initializes a transfer for an isochronous pipe.

The function usbd_transfer() initiates a transfer. Normally it returns USBD_IN_PROGRESS to indicate that the transfer has been queued. If the USB stack is operating in polling mode, or if the transfer is synchronous, then USBD_NORMAL_COMPLETION may be returned. Other return values indicate that the transfer could not be initiated due to an error. The usbd_sync_transfer() function executes a transfer synchronously. It will sleep waiting for the transfer to complete and then return the transfer status. Note that if the transfer has a callback routine, this will be invoked before usbd_sync_transfer() returns.

The usbd_intr_transfer() and usbd_bulk_transfer() functions set up a transfer and wait synchronously for it to complete but they allows signals to interrupt the wait. They returns USBD_INTERRUPTED if the transfer was interrupted by a signal. XXX these two functions are identical apart from their names.

The function usbd_get_xfer_status() retrieves various information from a completed transfer. If the priv parameter is not NULL then the callback private argument is stored in *priv. If buffer is not NULL then the transfer buffer pointer is stored in *buffer. The actual number of bytes transferred is stored in *count if count is not NULL. Finally, the transfer status is stored in *status if status is not NULL.

The usbd_clear_endpoint_stall() function clears an endpoint stall condition synchronously, i.e. it sleeps waiting for the stall clear request to complete. The function usbd_clear_endpoint_stall_async() performs the same function asynchronously, but it provides no way to determine when the request completed, or whether it was successful. The usbd_clear_endpoint_toggle() function instructs the host controller driver to reset the toggle bit on a pipe. This is used when manually clearing an endpoint stall using a control pipe request, in order to ensure that the host controller driver and the USB device restart with the same toggle value.

Normally the USB subsystem maps and copies data to and from DMA-capable memory each time a transfer is performed. The function usbd_alloc_buffer() allocates a permanent DMA-capable buffer associated with the transfer to avoid this overhead. The return value is the virtual address of the buffer. Any time that usbd_setup_xfer() is called on the transfer with the USBD_NO_COPY flag enabled, the allocated buffer will be used directly and the buffer argument passed to usbd_setup_xfer() will be ignored. The usbd_get_buffer() function returns a pointer to the virtual address of a buffer previously allocated by usbd_alloc_buffer(). Finally, usbd_free_buffer() deallocates the buffer.

The usbd_errstr() function converts a status code into a string for display.

The function usbd_set_polling() enables or disables polling mode. In polling mode, all operations will busy-wait for the device to respond, so its use is effectively limited to boot time and kernel debuggers. It is important to match up calls that enable and disable polling mode, because the implementation just increments a polling reference count when on is non-zero and decrements it when on is zero. The usbd_dopoll() causes the host controller driver to poll for any activity. This should only be used when polling mode is enabled.

The usbd_ratecheck() function is used to limit the rate at which error messages are printed to approximately once per second. The last argument should point at a persistent struct timeval. A value of 1 will be returned if a message should be printed, but if usbd_ratecheck() has already been called with the same struct timeval parameter in the last second then 0 is returned and the error message should be suppressed.

The functions usb_detach_wait() and usb_detach_wakeup() are used to wait for references to drain before completing the detachment of a device. The usb_detach_wait() function will wait up to 60 seconds to receive a signal from usb_detach_wait().

USB Descriptors
The USB specification defines a number of standard descriptors by which USB devices report their attributes. These descriptors are fixed-format structures that all USB devices make available through USB control pipe requests.

Every USB device has exactly one USB device descriptor. The USB subsystem retrieves this automatically when a device is attached, and a copy of the descriptor is kept in memory. The usbd_get_device_descriptor() function returns a pointer to the descriptor. The device descriptor structure is defined in <dev/usb/usb.h> as follows:

typedef struct {

uByte

bLength;

uByte

bDescriptorType;

uWord

bcdUSB;

#define UD_USB_2_0

0x0200

#define UD_IS_USB2(d) (UGETW((d)->bcdUSB) >= UD_USB_2_0)

uByte

bDeviceClass;

uByte

bDeviceSubClass;

uByte

bDeviceProtocol;

uByte

bMaxPacketSize;

/* The fields below are not part of the initial descriptor. */

uWord

idVendor;

uWord

idProduct;

uWord

bcdDevice;

uByte

iManufacturer;

uByte

iProduct;

uByte

iSerialNumber;

uByte

bNumConfigurations;

} UPACKED usb_device_descriptor_t;
#define USB_DEVICE_DESCRIPTOR_SIZE 18

USB devices have at least one configuration descriptor. The bNumConfigurations field of the device descriptor specifies the number of configuration descriptors that a device supports. The usbd_get_config_desc() function retrieves a particular configuration descriptor from the device and the usbd_get_config_desc_full() function retrieves a full wTotalLength length configuration descriptor, which includes all related interface and endpoint descriptors. Only one configuration may be active at a time. The usbd_set_config_index() function activates a specified configuration. The configuration descriptor structure is defined in <dev/usb/usb.h> as follows:

typedef struct {

uByte

bLength;

uByte

bDescriptorType;

uWord

wTotalLength;

uByte

bNumInterface;

uByte

bConfigurationValue;

uByte

iConfiguration;

uByte

bmAttributes;

#define UC_BUS_POWERED

0x80

#define UC_SELF_POWERED

0x40

#define UC_REMOTE_WAKEUP

0x20

uByte

bMaxPower; /* max current in 2 mA units */

#define UC_POWER_FACTOR 2
} UPACKED usb_config_descriptor_t;
#define USB_CONFIG_DESCRIPTOR_SIZE 9

Each device configuration provides one or more interfaces. The bNumInterface field of the configuration descriptor specifies the number of interfaces associated with a device configuration. Interfaces are described by an interface descriptor, which is defined in <dev/usb/usb.h> as follows:

typedef struct {

uByte

bLength;

uByte

bDescriptorType;

uByte

bInterfaceNumber;

uByte

bAlternateSetting;

uByte

bNumEndpoints;

uByte

bInterfaceClass;

uByte

bInterfaceSubClass;

uByte

bInterfaceProtocol;

uByte

iInterface;

} UPACKED usb_interface_descriptor_t;
#define USB_INTERFACE_DESCRIPTOR_SIZE 9

Configurations may also have alternate interfaces with the same bInterfaceNumber but different bAlternateSetting values. These alternate interface settings may be selected by passing a non-zero altidx parameter to usbd_set_interface().

Interfaces have zero or more endpoints, and each endpoint has an endpoint descriptor. Note that endpoint zero, which is always present, does not have an endpoint descriptor, and it is never included in the bNumEndpoints count of endpoints. The endpoint descriptor is defined in <dev/usb/usb.h> as follows:

typedef struct {

uByte

bLength;

uByte

bDescriptorType;

uByte

bEndpointAddress;

#define UE_GET_DIR(a)

((a) & 0x80)

#define UE_SET_DIR(a,d) ((a) | (((d)&1) << 7))

#define UE_DIR_IN

0x80

#define UE_DIR_OUT

0x00

#define UE_ADDR

0x0f

#define UE_GET_ADDR(a)

((a) & UE_ADDR)

uByte

bmAttributes;

#define UE_XFERTYPE

0x03

#define

UE_CONTROL

0x00

#define

UE_ISOCHRONOUS 0x01

#define

UE_BULK

0x02

#define

UE_INTERRUPT

0x03

#define UE_GET_XFERTYPE(a)

((a) & UE_XFERTYPE)

#define UE_ISO_TYPE

0x0c

#define

UE_ISO_ASYNC

0x04

#define

UE_ISO_ADAPT

0x08

#define

UE_ISO_SYNC

0x0c

#define UE_GET_ISO_TYPE(a)

((a) & UE_ISO_TYPE)

uWord

wMaxPacketSize;

uByte

bInterval;

} UPACKED usb_endpoint_descriptor_t;
#define USB_ENDPOINT_DESCRIPTOR_SIZE 7

RETURN VALUES

Many functions return a usbd_status type to indicate the outcome of the operation. If the operation completed successfully then USBD_NORMAL_COMPLETION is returned. Operations that have been started but not yet completed will return USBD_IN_PROGRESS. Other errors usually indicate a problem. Error codes can be converted to strings using usbd_errstr().

ERRORS
[USBD_PENDING_REQUESTS]

A pipe could not be closed because there are active requests.

[USBD_NOT_STARTED]

The transfer has not yet been started.

[USBD_INVAL]

An invalid value was supplied.

[USBD_NOMEM]

An attempt to allocate memory failed.

[USBD_CANCELLED]

The transfer was aborted.

[USBD_BAD_ADDRESS]

The specified endpoint address was not found.

[USBD_IN_USE]

The endpoint is already in use, or the configuration cannot be changed because some of its endpoints are in use.

[USBD_NO_ADDR]

No free USB devices addresses were found to assign to the device.

[USBD_SET_ADDR_FAILED]

The device address could not be set.

[USBD_NO_POWER]

Insufficient power was available for the device.

[USBD_TOO_DEEP]

Too many levels of chained hubs were found.

[USBD_IOERROR]

There was an error communicating with the device.

[USBD_NOT_CONFIGURED]

An operation that requires an active configuration was attempted while the device was in an unconfigured state.

[USBD_TIMEOUT]

A transfer timed out.

[USBD_SHORT_XFER]

A transfer that disallowed short data lengths completed with less than the requested length transferred.

[USBD_STALLED]

A transfer failed because the pipe is stalled.

[USBD_INTERRUPTED]

An interruptible operation caught a signal.

SEE ALSO

usb(4)

HISTORY

The USB driver interface first appeared in FreeBSD 3.0.

AUTHORS

The USB driver was written by Lennart Augustsson for the NetBSD project.

This manual page was written by Ian Dowse 〈iedowse@FreeBSD.org〉.

MidnightBSD 0.3 December 30, 2005 MidnightBSD 0.3