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usb_clear_halt(9) [centos man page]

USB_CLEAR_HALT(9)						   USB Core APIs						 USB_CLEAR_HALT(9)

NAME
usb_clear_halt - tells device to clear endpoint halt/stall condition SYNOPSIS
int usb_clear_halt(struct usb_device * dev, int pipe); ARGUMENTS
dev device whose endpoint is halted pipe endpoint "pipe" being cleared CONTEXT
!in_interrupt () DESCRIPTION
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. RETURN
Zero on success, or else the status code returned by the underlying usb_control_msg call. COPYRIGHT
Kernel Hackers Manual 3.10 June 2014 USB_CLEAR_HALT(9)

Check Out this Related Man Page

USB_BULK_MSG(9) 						   USB Core APIs						   USB_BULK_MSG(9)

NAME
usb_bulk_msg - Builds a bulk urb, sends it off and waits for completion SYNOPSIS
int usb_bulk_msg(struct usb_device * usb_dev, unsigned int pipe, void * data, int len, int * actual_length, int timeout); ARGUMENTS
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
!in_interrupt () DESCRIPTION
This function sends a simple bulk message to a specified endpoint and waits for the message to complete, or timeout. If successful, it returns 0, otherwise a negative error number. The number of actual bytes transferred will be stored in the actual_length paramater. Don't use this function from within an interrupt context, like a bottom half handler. 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. COPYRIGHT
Kernel Hackers Manual 2.6. July 2010 USB_BULK_MSG(9)

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