Implement an ioctl to support the USMTMC-USB488 READ_STATUS_BYTE operation.

Background:
When performing a read on an instrument that is executing a function
that runs longer than the USB timeout the instrument may hang and
require a device reset to recover. The READ_STATUS_BYTE operation
always returns even when the instrument is busy permitting to poll
for the appropriate condition. This capability is referred to in
instrument application notes on synchronizing acquisitions for other
platforms.

Signed-off-by: Dave Penkler <dpenkler@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/include/uapi/linux/usb/tmc.h b/include/uapi/linux/usb/tmc.h
index c045ae1..7e5ced8 100644
--- a/include/uapi/linux/usb/tmc.h
+++ b/include/uapi/linux/usb/tmc.h
@@ -30,6 +30,7 @@
 #define USBTMC_REQUEST_CHECK_CLEAR_STATUS		6
 #define USBTMC_REQUEST_GET_CAPABILITIES			7
 #define USBTMC_REQUEST_INDICATOR_PULSE			64
+#define USBTMC488_REQUEST_READ_STATUS_BYTE		128
 
 /* Request values for USBTMC driver's ioctl entry point */
 #define USBTMC_IOC_NR			91
@@ -39,5 +40,6 @@
 #define USBTMC_IOCTL_ABORT_BULK_IN	_IO(USBTMC_IOC_NR, 4)
 #define USBTMC_IOCTL_CLEAR_OUT_HALT	_IO(USBTMC_IOC_NR, 6)
 #define USBTMC_IOCTL_CLEAR_IN_HALT	_IO(USBTMC_IOC_NR, 7)
+#define USBTMC488_IOCTL_READ_STB	_IOR(USBTMC_IOC_NR, 18, unsigned char)
 
 #endif