usb_control_msg
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Name

usb_control_msg — Builds a control urb, sends it off and waits for completion

Synopsis

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);

Arguments

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

!in_interrupt ()

Description

This function sends a simple control message to a specified endpoint and waits for the message to complete, or timeout.

If successful, it returns the number of bytes transferred, otherwise a negative error number.

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.

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