usb: usbtmc: Add ioctl USBTMC_IOCTL_WRITE_RESULT

ioctl USBTMC_IOCTL_WRITE_RESULT copies current out_transfer_size
to given __u32 pointer and returns current out_status of the last
(asnynchronous) USBTMC_IOCTL_WRITE call.
Signed-off-by: Guido Kiener <guido.kiener@rohde-schwarz.com>
Reviewed-by: Steve Bayless <steve_bayless@keysight.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/class/usbtmc.c

@@ -893,6 +893,26 @@ static ssize_t usbtmc_ioctl_generic_write(struct usbtmc_file_data *file_data,
 	return retval;
 }
 
+/*
+ * Get the generic write result
+ */
+static ssize_t usbtmc_ioctl_write_result(struct usbtmc_file_data *file_data,
+				void __user *arg)
+{
+	u32 transferred;
+	int retval;
+
+	spin_lock_irq(&file_data->err_lock);
+	transferred = file_data->out_transfer_size;
+	retval = file_data->out_status;
+	spin_unlock_irq(&file_data->err_lock);
+
+	if (put_user(transferred, (__u32 __user *)arg))
+		return -EFAULT;
+
+	return retval;
+}
+
 /*
  * Sends a REQUEST_DEV_DEP_MSG_IN message on the Bulk-OUT endpoint.
  * @transfer_size: number of bytes to request from the device.
@@ -1748,6 +1768,11 @@ static long usbtmc_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 						    (void __user *)arg);
 		break;
 
+	case USBTMC_IOCTL_WRITE_RESULT:
+		retval = usbtmc_ioctl_write_result(file_data,
+						   (void __user *)arg);
+		break;
+
 	case USBTMC488_IOCTL_GET_CAPS:
 		retval = copy_to_user((void __user *)arg,
 				&data->usb488_caps,

include/uapi/linux/usb/tmc.h

@@ -86,6 +86,7 @@ struct usbtmc_message {
 #define USBTMC_IOCTL_EOM_ENABLE	        _IOW(USBTMC_IOC_NR, 11, __u8)
 #define USBTMC_IOCTL_CONFIG_TERMCHAR	_IOW(USBTMC_IOC_NR, 12, struct usbtmc_termchar)
 #define USBTMC_IOCTL_WRITE		_IOWR(USBTMC_IOC_NR, 13, struct usbtmc_message)
+#define USBTMC_IOCTL_WRITE_RESULT	_IOWR(USBTMC_IOC_NR, 15, __u32)
 
 #define USBTMC488_IOCTL_GET_CAPS	_IOR(USBTMC_IOC_NR, 17, unsigned char)
 #define USBTMC488_IOCTL_READ_STB	_IOR(USBTMC_IOC_NR, 18, unsigned char)