// SPDX-License-Identifier: GPL-2.0 /* * message.c - synchronous message handling * * Released under the GPLv2 only. */ #include <linux/acpi.h> #include <linux/pci.h> /* for scatterlist macros */ #include <linux/usb.h> #include <linux/module.h> #include <linux/of.h> #include <linux/slab.h> #include <linux/mm.h> #include <linux/timer.h> #include <linux/ctype.h> #include <linux/nls.h> #include <linux/device.h> #include <linux/scatterlist.h> #include <linux/usb/cdc.h> #include <linux/usb/quirks.h> #include <linux/usb/hcd.h> /* for usbcore internals */ #include <linux/usb/of.h> #include <asm/byteorder.h> #include "usb.h" static void cancel_async_set_config(struct usb_device *udev); struct api_context { … }; static void usb_api_blocking_completion(struct urb *urb) { … } /* * Starts urb and waits for completion or timeout. Note that this call * is NOT interruptible. Many device driver i/o requests should be * interruptible and therefore these drivers should implement their * own interruptible routines. */ static int usb_start_wait_urb(struct urb *urb, int timeout, int *actual_length) { … } /*-------------------------------------------------------------------*/ /* returns status (negative) or length (positive) */ static int usb_internal_control_msg(struct usb_device *usb_dev, unsigned int pipe, struct usb_ctrlrequest *cmd, void *data, int len, int timeout) { … } /** * usb_control_msg - Builds a control urb, sends it off and waits for completion * @dev: pointer to the usb device to send the message to * @pipe: endpoint "pipe" to send the message to * @request: USB message request value * @requesttype: USB message request type value * @value: USB message value * @index: USB message index value * @data: pointer to the data to send * @size: length in bytes of the data to send * @timeout: time in msecs to wait for the message to complete before timing * out (if 0 the wait is forever) * * Context: task context, might sleep. * * This function sends a simple control message to a specified endpoint and * waits for the message to complete, or timeout. * * Don't use this function from within an interrupt context. If you need * an asynchronous message, or need to send a message from within interrupt * context, use usb_submit_urb(). If a thread in your driver uses this call, * make sure your disconnect() method can wait for it to complete. Since you * don't have a handle on the URB used, you can't cancel the request. * * Return: If successful, the number of bytes transferred. Otherwise, a negative * error number. */ int usb_control_msg(struct usb_device *dev, unsigned int pipe, __u8 request, __u8 requesttype, __u16 value, __u16 index, void *data, __u16 size, int timeout) { … } EXPORT_SYMBOL_GPL(…); /** * usb_control_msg_send - Builds a control "send" message, sends it off and waits for completion * @dev: pointer to the usb device to send the message to * @endpoint: endpoint to send the message to * @request: USB message request value * @requesttype: USB message request type value * @value: USB message value * @index: USB message index value * @driver_data: pointer to the data to send * @size: length in bytes of the data to send * @timeout: time in msecs to wait for the message to complete before timing * out (if 0 the wait is forever) * @memflags: the flags for memory allocation for buffers * * Context: !in_interrupt () * * This function sends a control message to a specified endpoint that is not * expected to fill in a response (i.e. a "send message") and waits for the * message to complete, or timeout. * * Do not use this function from within an interrupt context. If you need * an asynchronous message, or need to send a message from within interrupt * context, use usb_submit_urb(). If a thread in your driver uses this call, * make sure your disconnect() method can wait for it to complete. Since you * don't have a handle on the URB used, you can't cancel the request. * * The data pointer can be made to a reference on the stack, or anywhere else, * as it will not be modified at all. This does not have the restriction that * usb_control_msg() has where the data pointer must be to dynamically allocated * memory (i.e. memory that can be successfully DMAed to a device). * * Return: If successful, 0 is returned, Otherwise, a negative error number. */ int usb_control_msg_send(struct usb_device *dev, __u8 endpoint, __u8 request, __u8 requesttype, __u16 value, __u16 index, const void *driver_data, __u16 size, int timeout, gfp_t memflags) { … } EXPORT_SYMBOL_GPL(…); /** * usb_control_msg_recv - Builds a control "receive" message, sends it off and waits for completion * @dev: pointer to the usb device to send the message to * @endpoint: endpoint to send the message to * @request: USB message request value * @requesttype: USB message request type value * @value: USB message value * @index: USB message index value * @driver_data: pointer to the data to be filled in by the message * @size: length in bytes of the data to be received * @timeout: time in msecs to wait for the message to complete before timing * out (if 0 the wait is forever) * @memflags: the flags for memory allocation for buffers * * Context: !in_interrupt () * * This function sends a control message to a specified endpoint that is * expected to fill in a response (i.e. a "receive message") and waits for the * message to complete, or timeout. * * Do not use this function from within an interrupt context. If you need * an asynchronous message, or need to send a message from within interrupt * context, use usb_submit_urb(). If a thread in your driver uses this call, * make sure your disconnect() method can wait for it to complete. Since you * don't have a handle on the URB used, you can't cancel the request. * * The data pointer can be made to a reference on the stack, or anywhere else * that can be successfully written to. This function does not have the * restriction that usb_control_msg() has where the data pointer must be to * dynamically allocated memory (i.e. memory that can be successfully DMAed to a * device). * * The "whole" message must be properly received from the device in order for * this function to be successful. If a device returns less than the expected * amount of data, then the function will fail. Do not use this for messages * where a variable amount of data might be returned. * * Return: If successful, 0 is returned, Otherwise, a negative error number. */ int usb_control_msg_recv(struct usb_device *dev, __u8 endpoint, __u8 request, __u8 requesttype, __u16 value, __u16 index, void *driver_data, __u16 size, int timeout, gfp_t memflags) { … } EXPORT_SYMBOL_GPL(…); /** * usb_interrupt_msg - Builds an interrupt urb, sends it off and waits for completion * @usb_dev: pointer to the usb device to send the message to * @pipe: endpoint "pipe" to send the message to * @data: pointer to the data to send * @len: length in bytes of the data to send * @actual_length: pointer to a location to put the actual length transferred * in bytes * @timeout: time in msecs to wait for the message to complete before * timing out (if 0 the wait is forever) * * Context: task context, might sleep. * * This function sends a simple interrupt message to a specified endpoint and * waits for the message to complete, or timeout. * * Don't use this function from within an interrupt context. If you need * an asynchronous message, or need to send a message from within interrupt * context, use usb_submit_urb() If a thread in your driver uses this call, * make sure your disconnect() method can wait for it to complete. Since you * don't have a handle on the URB used, you can't cancel the request. * * Return: * If successful, 0. Otherwise a negative error number. The number of actual * bytes transferred will be stored in the @actual_length parameter. */ int usb_interrupt_msg(struct usb_device *usb_dev, unsigned int pipe, void *data, int len, int *actual_length, int timeout) { … } EXPORT_SYMBOL_GPL(…); /** * usb_bulk_msg - Builds a bulk urb, sends it off and waits for completion * @usb_dev: pointer to the usb device to send the message to * @pipe: endpoint "pipe" to send the message to * @data: pointer to the data to send * @len: length in bytes of the data to send * @actual_length: pointer to a location to put the actual length transferred * in bytes * @timeout: time in msecs to wait for the message to complete before * timing out (if 0 the wait is forever) * * Context: task context, might sleep. * * This function sends a simple bulk message to a specified endpoint * and waits for the message to complete, or timeout. * * Don't use this function from within an interrupt context. If you need * an asynchronous message, or need to send a message from within interrupt * context, use usb_submit_urb() If a thread in your driver uses this call, * make sure your disconnect() method can wait for it to complete. Since you * don't have a handle on the URB used, you can't cancel the request. * * Because there is no usb_interrupt_msg() and no USBDEVFS_INTERRUPT ioctl, * users are forced to abuse this routine by using it to submit URBs for * interrupt endpoints. We will take the liberty of creating an interrupt URB * (with the default interval) if the target is an interrupt endpoint. * * Return: * If successful, 0. Otherwise a negative error number. The number of actual * bytes transferred will be stored in the @actual_length parameter. * */ int usb_bulk_msg(struct usb_device *usb_dev, unsigned int pipe, void *data, int len, int *actual_length, int timeout) { … } EXPORT_SYMBOL_GPL(…); /*-------------------------------------------------------------------*/ static void sg_clean(struct usb_sg_request *io) { … } static void sg_complete(struct urb *urb) { … } /** * usb_sg_init - initializes scatterlist-based bulk/interrupt I/O request * @io: request block being initialized. until usb_sg_wait() returns, * treat this as a pointer to an opaque block of memory, * @dev: the usb device that will send or receive the data * @pipe: endpoint "pipe" used to transfer the data * @period: polling rate for interrupt endpoints, in frames or * (for high speed endpoints) microframes; ignored for bulk * @sg: scatterlist entries * @nents: how many entries in the scatterlist * @length: how many bytes to send from the scatterlist, or zero to * send every byte identified in the list. * @mem_flags: SLAB_* flags affecting memory allocations in this call * * This initializes a scatter/gather request, allocating resources such as * I/O mappings and urb memory (except maybe memory used by USB controller * drivers). * * The request must be issued using usb_sg_wait(), which waits for the I/O to * complete (or to be canceled) and then cleans up all resources allocated by * usb_sg_init(). * * The request may be canceled with usb_sg_cancel(), either before or after * usb_sg_wait() is called. * * Return: Zero for success, else a negative errno value. */ int usb_sg_init(struct usb_sg_request *io, struct usb_device *dev, unsigned pipe, unsigned period, struct scatterlist *sg, int nents, size_t length, gfp_t mem_flags) { … } EXPORT_SYMBOL_GPL(…); /** * usb_sg_wait - synchronously execute scatter/gather request * @io: request block handle, as initialized with usb_sg_init(). * some fields become accessible when this call returns. * * Context: task context, might sleep. * * This function blocks until the specified I/O operation completes. It * leverages the grouping of the related I/O requests to get good transfer * rates, by queueing the requests. At higher speeds, such queuing can * significantly improve USB throughput. * * There are three kinds of completion for this function. * * (1) success, where io->status is zero. The number of io->bytes * transferred is as requested. * (2) error, where io->status is a negative errno value. The number * of io->bytes transferred before the error is usually less * than requested, and can be nonzero. * (3) cancellation, a type of error with status -ECONNRESET that * is initiated by usb_sg_cancel(). * * When this function returns, all memory allocated through usb_sg_init() or * this call will have been freed. The request block parameter may still be * passed to usb_sg_cancel(), or it may be freed. It could also be * reinitialized and then reused. * * Data Transfer Rates: * * Bulk transfers are valid for full or high speed endpoints. * The best full speed data rate is 19 packets of 64 bytes each * per frame, or 1216 bytes per millisecond. * The best high speed data rate is 13 packets of 512 bytes each * per microframe, or 52 KBytes per millisecond. * * The reason to use interrupt transfers through this API would most likely * be to reserve high speed bandwidth, where up to 24 KBytes per millisecond * could be transferred. That capability is less useful for low or full * speed interrupt endpoints, which allow at most one packet per millisecond, * of at most 8 or 64 bytes (respectively). * * It is not necessary to call this function to reserve bandwidth for devices * under an xHCI host controller, as the bandwidth is reserved when the * configuration or interface alt setting is selected. */ void usb_sg_wait(struct usb_sg_request *io) { … } EXPORT_SYMBOL_GPL(…); /** * usb_sg_cancel - stop scatter/gather i/o issued by usb_sg_wait() * @io: request block, initialized with usb_sg_init() * * This stops a request after it has been started by usb_sg_wait(). * It can also prevents one initialized by usb_sg_init() from starting, * so that call just frees resources allocated to the request. */ void usb_sg_cancel(struct usb_sg_request *io) { … } EXPORT_SYMBOL_GPL(…); /*-------------------------------------------------------------------*/ /** * usb_get_descriptor - issues a generic GET_DESCRIPTOR request * @dev: the device whose descriptor is being retrieved * @type: the descriptor type (USB_DT_*) * @index: the number of the descriptor * @buf: where to put the descriptor * @size: how big is "buf"? * * Context: task context, might sleep. * * Gets a USB descriptor. Convenience functions exist to simplify * getting some types of descriptors. Use * usb_get_string() or usb_string() for USB_DT_STRING. * Device (USB_DT_DEVICE) and configuration descriptors (USB_DT_CONFIG) * are part of the device structure. * In addition to a number of USB-standard descriptors, some * devices also use class-specific or vendor-specific descriptors. * * This call is synchronous, and may not be used in an interrupt context. * * Return: The number of bytes received on success, or else the status code * returned by the underlying usb_control_msg() call. */ int usb_get_descriptor(struct usb_device *dev, unsigned char type, unsigned char index, void *buf, int size) { … } EXPORT_SYMBOL_GPL(…); /** * usb_get_string - gets a string descriptor * @dev: the device whose string descriptor is being retrieved * @langid: code for language chosen (from string descriptor zero) * @index: the number of the descriptor * @buf: where to put the string * @size: how big is "buf"? * * Context: task context, might sleep. * * Retrieves a string, encoded using UTF-16LE (Unicode, 16 bits per character, * in little-endian byte order). * The usb_string() function will often be a convenient way to turn * these strings into kernel-printable form. * * Strings may be referenced in device, configuration, interface, or other * descriptors, and could also be used in vendor-specific ways. * * This call is synchronous, and may not be used in an interrupt context. * * Return: The number of bytes received on success, or else the status code * returned by the underlying usb_control_msg() call. */ static int usb_get_string(struct usb_device *dev, unsigned short langid, unsigned char index, void *buf, int size) { … } static void usb_try_string_workarounds(unsigned char *buf, int *length) { … } static int usb_string_sub(struct usb_device *dev, unsigned int langid, unsigned int index, unsigned char *buf) { … } static int usb_get_langid(struct usb_device *dev, unsigned char *tbuf) { … } /** * usb_string - returns UTF-8 version of a string descriptor * @dev: the device whose string descriptor is being retrieved * @index: the number of the descriptor * @buf: where to put the string * @size: how big is "buf"? * * Context: task context, might sleep. * * This converts the UTF-16LE encoded strings returned by devices, from * usb_get_string_descriptor(), to null-terminated UTF-8 encoded ones * that are more usable in most kernel contexts. Note that this function * chooses strings in the first language supported by the device. * * This call is synchronous, and may not be used in an interrupt context. * * Return: length of the string (>= 0) or usb_control_msg status (< 0). */ int usb_string(struct usb_device *dev, int index, char *buf, size_t size) { … } EXPORT_SYMBOL_GPL(…); /* one UTF-8-encoded 16-bit character has at most three bytes */ #define MAX_USB_STRING_SIZE … /** * usb_cache_string - read a string descriptor and cache it for later use * @udev: the device whose string descriptor is being read * @index: the descriptor index * * Return: A pointer to a kmalloc'ed buffer containing the descriptor string, * or %NULL if the index is 0 or the string could not be read. */ char *usb_cache_string(struct usb_device *udev, int index) { … } EXPORT_SYMBOL_GPL(…); /* * usb_get_device_descriptor - read the device descriptor * @udev: the device whose device descriptor should be read * * Context: task context, might sleep. * * Not exported, only for use by the core. If drivers really want to read * the device descriptor directly, they can call usb_get_descriptor() with * type = USB_DT_DEVICE and index = 0. * * Returns: a pointer to a dynamically allocated usb_device_descriptor * structure (which the caller must deallocate), or an ERR_PTR value. */ struct usb_device_descriptor *usb_get_device_descriptor(struct usb_device *udev) { … } /* * usb_set_isoch_delay - informs the device of the packet transmit delay * @dev: the device whose delay is to be informed * Context: task context, might sleep * * Since this is an optional request, we don't bother if it fails. */ int usb_set_isoch_delay(struct usb_device *dev) { … } /** * usb_get_status - issues a GET_STATUS call * @dev: the device whose status is being checked * @recip: USB_RECIP_*; for device, interface, or endpoint * @type: USB_STATUS_TYPE_*; for standard or PTM status types * @target: zero (for device), else interface or endpoint number * @data: pointer to two bytes of bitmap data * * Context: task context, might sleep. * * Returns device, interface, or endpoint status. Normally only of * interest to see if the device is self powered, or has enabled the * remote wakeup facility; or whether a bulk or interrupt endpoint * is halted ("stalled"). * * Bits in these status bitmaps are set using the SET_FEATURE request, * and cleared using the CLEAR_FEATURE request. The usb_clear_halt() * function should be used to clear halt ("stall") status. * * This call is synchronous, and may not be used in an interrupt context. * * Returns 0 and the status value in *@data (in host byte order) on success, * or else the status code from the underlying usb_control_msg() call. */ int usb_get_status(struct usb_device *dev, int recip, int type, int target, void *data) { … } EXPORT_SYMBOL_GPL(…); /** * usb_clear_halt - tells device to clear endpoint halt/stall condition * @dev: device whose endpoint is halted * @pipe: endpoint "pipe" being cleared * * Context: task context, might sleep. * * This is used to clear halt conditions for bulk and interrupt endpoints, * as reported by URB completion status. Endpoints that are halted are * sometimes referred to as being "stalled". Such endpoints are unable * to transmit or receive data until the halt status is cleared. Any URBs * queued for such an endpoint should normally be unlinked by the driver * before clearing the halt condition, as described in sections 5.7.5 * and 5.8.5 of the USB 2.0 spec. * * Note that control and isochronous endpoints don't halt, although control * endpoints report "protocol stall" (for unsupported requests) using the * same status code used to report a true stall. * * This call is synchronous, and may not be used in an interrupt context. * If a thread in your driver uses this call, make sure your disconnect() * method can wait for it to complete. * * Return: Zero on success, or else the status code returned by the * underlying usb_control_msg() call. */ int usb_clear_halt(struct usb_device *dev, int pipe) { … } EXPORT_SYMBOL_GPL(…); static int create_intf_ep_devs(struct usb_interface *intf) { … } static void remove_intf_ep_devs(struct usb_interface *intf) { … } /** * usb_disable_endpoint -- Disable an endpoint by address * @dev: the device whose endpoint is being disabled * @epaddr: the endpoint's address. Endpoint number for output, * endpoint number + USB_DIR_IN for input * @reset_hardware: flag to erase any endpoint state stored in the * controller hardware * * Disables the endpoint for URB submission and nukes all pending URBs. * If @reset_hardware is set then also deallocates hcd/hardware state * for the endpoint. */ void usb_disable_endpoint(struct usb_device *dev, unsigned int epaddr, bool reset_hardware) { … } /** * usb_reset_endpoint - Reset an endpoint's state. * @dev: the device whose endpoint is to be reset * @epaddr: the endpoint's address. Endpoint number for output, * endpoint number + USB_DIR_IN for input * * Resets any host-side endpoint state such as the toggle bit, * sequence number or current window. */ void usb_reset_endpoint(struct usb_device *dev, unsigned int epaddr) { … } EXPORT_SYMBOL_GPL(…); /** * usb_disable_interface -- Disable all endpoints for an interface * @dev: the device whose interface is being disabled * @intf: pointer to the interface descriptor * @reset_hardware: flag to erase any endpoint state stored in the * controller hardware * * Disables all the endpoints for the interface's current altsetting. */ void usb_disable_interface(struct usb_device *dev, struct usb_interface *intf, bool reset_hardware) { … } /* * usb_disable_device_endpoints -- Disable all endpoints for a device * @dev: the device whose endpoints are being disabled * @skip_ep0: 0 to disable endpoint 0, 1 to skip it. */ static void usb_disable_device_endpoints(struct usb_device *dev, int skip_ep0) { … } /** * usb_disable_device - Disable all the endpoints for a USB device * @dev: the device whose endpoints are being disabled * @skip_ep0: 0 to disable endpoint 0, 1 to skip it. * * Disables all the device's endpoints, potentially including endpoint 0. * Deallocates hcd/hardware state for the endpoints (nuking all or most * pending urbs) and usbcore state for the interfaces, so that usbcore * must usb_set_configuration() before any interfaces could be used. */ void usb_disable_device(struct usb_device *dev, int skip_ep0) { … } /** * usb_enable_endpoint - Enable an endpoint for USB communications * @dev: the device whose interface is being enabled * @ep: the endpoint * @reset_ep: flag to reset the endpoint state * * Resets the endpoint state if asked, and sets dev->ep_{in,out} pointers. * For control endpoints, both the input and output sides are handled. */ void usb_enable_endpoint(struct usb_device *dev, struct usb_host_endpoint *ep, bool reset_ep) { … } /** * usb_enable_interface - Enable all the endpoints for an interface * @dev: the device whose interface is being enabled * @intf: pointer to the interface descriptor * @reset_eps: flag to reset the endpoints' state * * Enables all the endpoints for the interface's current altsetting. */ void usb_enable_interface(struct usb_device *dev, struct usb_interface *intf, bool reset_eps) { … } /** * usb_set_interface - Makes a particular alternate setting be current * @dev: the device whose interface is being updated * @interface: the interface being updated * @alternate: the setting being chosen. * * Context: task context, might sleep. * * This is used to enable data transfers on interfaces that may not * be enabled by default. Not all devices support such configurability. * Only the driver bound to an interface may change its setting. * * Within any given configuration, each interface may have several * alternative settings. These are often used to control levels of * bandwidth consumption. For example, the default setting for a high * speed interrupt endpoint may not send more than 64 bytes per microframe, * while interrupt transfers of up to 3KBytes per microframe are legal. * Also, isochronous endpoints may never be part of an * interface's default setting. To access such bandwidth, alternate * interface settings must be made current. * * Note that in the Linux USB subsystem, bandwidth associated with * an endpoint in a given alternate setting is not reserved until an URB * is submitted that needs that bandwidth. Some other operating systems * allocate bandwidth early, when a configuration is chosen. * * xHCI reserves bandwidth and configures the alternate setting in * usb_hcd_alloc_bandwidth(). If it fails the original interface altsetting * may be disabled. Drivers cannot rely on any particular alternate * setting being in effect after a failure. * * This call is synchronous, and may not be used in an interrupt context. * Also, drivers must not change altsettings while urbs are scheduled for * endpoints in that interface; all such urbs must first be completed * (perhaps forced by unlinking). If a thread in your driver uses this call, * make sure your disconnect() method can wait for it to complete. * * Return: Zero on success, or else the status code returned by the * underlying usb_control_msg() call. */ int usb_set_interface(struct usb_device *dev, int interface, int alternate) { … } EXPORT_SYMBOL_GPL(…); /** * usb_reset_configuration - lightweight device reset * @dev: the device whose configuration is being reset * * This issues a standard SET_CONFIGURATION request to the device using * the current configuration. The effect is to reset most USB-related * state in the device, including interface altsettings (reset to zero), * endpoint halts (cleared), and endpoint state (only for bulk and interrupt * endpoints). Other usbcore state is unchanged, including bindings of * usb device drivers to interfaces. * * Because this affects multiple interfaces, avoid using this with composite * (multi-interface) devices. Instead, the driver for each interface may * use usb_set_interface() on the interfaces it claims. Be careful though; * some devices don't support the SET_INTERFACE request, and others won't * reset all the interface state (notably endpoint state). Resetting the whole * configuration would affect other drivers' interfaces. * * The caller must own the device lock. * * Return: Zero on success, else a negative error code. * * If this routine fails the device will probably be in an unusable state * with endpoints disabled, and interfaces only partially enabled. */ int usb_reset_configuration(struct usb_device *dev) { … } EXPORT_SYMBOL_GPL(…); static void usb_release_interface(struct device *dev) { … } /* * usb_deauthorize_interface - deauthorize an USB interface * * @intf: USB interface structure */ void usb_deauthorize_interface(struct usb_interface *intf) { … } /* * usb_authorize_interface - authorize an USB interface * * @intf: USB interface structure */ void usb_authorize_interface(struct usb_interface *intf) { … } static int usb_if_uevent(const struct device *dev, struct kobj_uevent_env *env) { … } const struct device_type usb_if_device_type = …; static struct usb_interface_assoc_descriptor *find_iad(struct usb_device *dev, struct usb_host_config *config, u8 inum) { … } /* * Internal function to queue a device reset * See usb_queue_reset_device() for more details */ static void __usb_queue_reset_device(struct work_struct *ws) { … } /* * Internal function to set the wireless_status sysfs attribute * See usb_set_wireless_status() for more details */ static void __usb_wireless_status_intf(struct work_struct *ws) { … } /** * usb_set_wireless_status - sets the wireless_status struct member * @iface: the interface to modify * @status: the new wireless status * * Set the wireless_status struct member to the new value, and emit * sysfs changes as necessary. * * Returns: 0 on success, -EALREADY if already set. */ int usb_set_wireless_status(struct usb_interface *iface, enum usb_wireless_status status) { … } EXPORT_SYMBOL_GPL(…); /* * usb_set_configuration - Makes a particular device setting be current * @dev: the device whose configuration is being updated * @configuration: the configuration being chosen. * * Context: task context, might sleep. Caller holds device lock. * * This is used to enable non-default device modes. Not all devices * use this kind of configurability; many devices only have one * configuration. * * @configuration is the value of the configuration to be installed. * According to the USB spec (e.g. section 9.1.1.5), configuration values * must be non-zero; a value of zero indicates that the device in * unconfigured. However some devices erroneously use 0 as one of their * configuration values. To help manage such devices, this routine will * accept @configuration = -1 as indicating the device should be put in * an unconfigured state. * * USB device configurations may affect Linux interoperability, * power consumption and the functionality available. For example, * the default configuration is limited to using 100mA of bus power, * so that when certain device functionality requires more power, * and the device is bus powered, that functionality should be in some * non-default device configuration. Other device modes may also be * reflected as configuration options, such as whether two ISDN * channels are available independently; and choosing between open * standard device protocols (like CDC) or proprietary ones. * * Note that a non-authorized device (dev->authorized == 0) will only * be put in unconfigured mode. * * Note that USB has an additional level of device configurability, * associated with interfaces. That configurability is accessed using * usb_set_interface(). * * This call is synchronous. The calling context must be able to sleep, * must own the device lock, and must not hold the driver model's USB * bus mutex; usb interface driver probe() methods cannot use this routine. * * Returns zero on success, or else the status code returned by the * underlying call that failed. On successful completion, each interface * in the original device configuration has been destroyed, and each one * in the new configuration has been probed by all relevant usb device * drivers currently known to the kernel. */ int usb_set_configuration(struct usb_device *dev, int configuration) { … } EXPORT_SYMBOL_GPL(…); static LIST_HEAD(set_config_list); static DEFINE_SPINLOCK(set_config_lock); struct set_config_request { … }; /* Worker routine for usb_driver_set_configuration() */ static void driver_set_config_work(struct work_struct *work) { … } /* Cancel pending Set-Config requests for a device whose configuration * was just changed */ static void cancel_async_set_config(struct usb_device *udev) { … } /** * usb_driver_set_configuration - Provide a way for drivers to change device configurations * @udev: the device whose configuration is being updated * @config: the configuration being chosen. * Context: In process context, must be able to sleep * * Device interface drivers are not allowed to change device configurations. * This is because changing configurations will destroy the interface the * driver is bound to and create new ones; it would be like a floppy-disk * driver telling the computer to replace the floppy-disk drive with a * tape drive! * * Still, in certain specialized circumstances the need may arise. This * routine gets around the normal restrictions by using a work thread to * submit the change-config request. * * Return: 0 if the request was successfully queued, error code otherwise. * The caller has no way to know whether the queued request will eventually * succeed. */ int usb_driver_set_configuration(struct usb_device *udev, int config) { … } EXPORT_SYMBOL_GPL(…); /** * cdc_parse_cdc_header - parse the extra headers present in CDC devices * @hdr: the place to put the results of the parsing * @intf: the interface for which parsing is requested * @buffer: pointer to the extra headers to be parsed * @buflen: length of the extra headers * * This evaluates the extra headers present in CDC devices which * bind the interfaces for data and control and provide details * about the capabilities of the device. * * Return: number of descriptors parsed or -EINVAL * if the header is contradictory beyond salvage */ int cdc_parse_cdc_header(struct usb_cdc_parsed_header *hdr, struct usb_interface *intf, u8 *buffer, int buflen) { … } EXPORT_SYMBOL(…);
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