usb: usbtmc: Add ioctl for EOM bit

add USBTMC_IOCTL_EOM_ENABLE to specify EOM bit for next write()
call. Sets Bit 0 of field 'bmTransferAttributes' of DEV_DEP_MSG_OUT
Bulk-OUT Header.
Allows fine grained control over end of message handling on a
per file descriptor basis.

Reviewed-by: Steve Bayless <steve_bayless@keysight.com>
Tested-by: Dave Penkler <dpenkler@gmail.com>
Signed-off-by: Dave Penkler <dpenkler@gmail.com>
Signed-off-by: Guido Kiener <guido.kiener@rohde-schwarz.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/class/usbtmc.c

@@ -120,6 +120,7 @@ struct usbtmc_file_data {
 	u32            timeout;
 	u8             srq_byte;
 	atomic_t       srq_asserted;
+	u8             eom_val;
 };
 
 /* Forward declarations */
@@ -157,6 +158,7 @@ static int usbtmc_open(struct inode *inode, struct file *filp)
 	file_data->data = data;
 
 	file_data->timeout = USBTMC_TIMEOUT;
+	file_data->eom_val = 1;
 
 	INIT_LIST_HEAD(&file_data->file_elem);
 	spin_lock_irq(&data->dev_lock);
@@ -855,7 +857,7 @@ static ssize_t usbtmc_write(struct file *filp, const char __user *buf,
 			buffer[8] = 0;
 		} else {
 			this_part = remaining;
-			buffer[8] = 1;
+			buffer[8] = file_data->eom_val;
 		}
 
 		/* Setup IO buffer for DEV_DEP_MSG_OUT message */
@@ -1277,6 +1279,25 @@ static int usbtmc_ioctl_set_timeout(struct usbtmc_file_data *file_data,
 	return 0;
 }
 
+/*
+ * enables/disables sending EOM on write
+ */
+static int usbtmc_ioctl_eom_enable(struct usbtmc_file_data *file_data,
+				void __user *arg)
+{
+	u8 eom_enable;
+
+	if (copy_from_user(&eom_enable, arg, sizeof(eom_enable)))
+		return -EFAULT;
+
+	if (eom_enable > 1)
+		return -EINVAL;
+
+	file_data->eom_val = eom_enable;
+
+	return 0;
+}
+
 static long usbtmc_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
 	struct usbtmc_file_data *file_data;
@@ -1327,6 +1348,11 @@ static long usbtmc_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 						  (void __user *)arg);
 		break;
 
+	case USBTMC_IOCTL_EOM_ENABLE:
+		retval = usbtmc_ioctl_eom_enable(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

@@ -50,6 +50,8 @@
 #define USBTMC_IOCTL_CLEAR_IN_HALT	_IO(USBTMC_IOC_NR, 7)
 #define USBTMC_IOCTL_GET_TIMEOUT	_IOR(USBTMC_IOC_NR, 9, __u32)
 #define USBTMC_IOCTL_SET_TIMEOUT	_IOW(USBTMC_IOC_NR, 10, __u32)
+#define USBTMC_IOCTL_EOM_ENABLE	        _IOW(USBTMC_IOC_NR, 11, __u8)
+
 #define USBTMC488_IOCTL_GET_CAPS	_IOR(USBTMC_IOC_NR, 17, unsigned char)
 #define USBTMC488_IOCTL_READ_STB	_IOR(USBTMC_IOC_NR, 18, unsigned char)
 #define USBTMC488_IOCTL_REN_CONTROL	_IOW(USBTMC_IOC_NR, 19, unsigned char)