usb: usbtmc: add ioctl USBTMC_IOCTL_MSG_IN_ATTR

add ioctl USBTMC_IOCTL_MSG_IN_ATTR that returns the specific
bmTransferAttributes field of the last DEV_DEP_MSG_IN Bulk-IN
header. This header is received by the read() function. The
meaning of the (u8) bitmap bmTransferAttributes is:

Bit 0 = EOM flag is set when the last transfer of a USBTMC
message is received.

Bit 1 = is set when the last byte is a termchar (e.g. '\n').
Note that this bit is always zero when the device does not support
the termchar feature or when termchar detection is not enabled
(see ioctl USBTMC_IOCTL_CONFIG_TERMCHAR).

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

@@ -131,6 +131,7 @@ struct usbtmc_file_data {
 	u8             srq_byte;
 	atomic_t       srq_asserted;
 	atomic_t       closing;
+	u8             bmTransferAttributes; /* member of DEV_DEP_MSG_IN */
 
 	u8             eom_val;
 	u8             term_char;
@@ -1435,6 +1436,8 @@ static ssize_t usbtmc_read(struct file *filp, char __user *buf,
 				       (buffer[6] << 16) +
 				       (buffer[7] << 24);
 
+			file_data->bmTransferAttributes = buffer[8];
+
 			if (n_characters > this_part) {
 				dev_err(dev, "Device wants to return more data than requested: %u > %zu\n", n_characters, count);
 				if (data->auto_abort)
@@ -2199,6 +2202,11 @@ static long usbtmc_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 						  (__u32 __user *)arg);
 		break;
 
+	case USBTMC_IOCTL_MSG_IN_ATTR:
+		retval = put_user(file_data->bmTransferAttributes,
+				  (__u8 __user *)arg);
+		break;
+
 	case USBTMC_IOCTL_CANCEL_IO:
 		retval = usbtmc_ioctl_cancel_io(file_data);
 		break;

include/uapi/linux/usb/tmc.h

@@ -98,6 +98,8 @@ struct usbtmc_message {
 #define USBTMC488_IOCTL_TRIGGER		_IO(USBTMC_IOC_NR, 22)
 #define USBTMC488_IOCTL_WAIT_SRQ	_IOW(USBTMC_IOC_NR, 23, __u32)
 
+#define USBTMC_IOCTL_MSG_IN_ATTR	_IOR(USBTMC_IOC_NR, 24, __u8)
+
 /* Cancel and cleanup asynchronous calls */
 #define USBTMC_IOCTL_CANCEL_IO		_IO(USBTMC_IOC_NR, 35)
 #define USBTMC_IOCTL_CLEANUP_IO		_IO(USBTMC_IOC_NR, 36)