usb_control_msg (9) Linux Manual Page
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.
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.
Return
If successful, the number of bytes transferred. Otherwise, a negative error number.