usb: usbtmc: Add ioctls to set/get usb timeout

Add ioctls USBTMC_IOCTL_GET_TIMEOUT / USBTMC_IOCTL_SET_TIMEOUT to
get/set I/O timeout for specific file handle.

Different operations on an instrument can take different lengths of
time thus it is important to be able to set the timeout slightly
longer than the expected duration of each operation to optimise the
responsiveness of the application. As the instrument may be shared by
multiple applications the timeout should be settable on a per file
descriptor basis.

Tested-by: Dave Penkler <dpenkler@gmail.com>
Reviewed-by: Steve Bayless <steve_bayless@keysight.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

@@ -30,6 +30,8 @@
  */
 #define USBTMC_SIZE_IOBUFFER	2048
 
+/* Minimum USB timeout (in milliseconds) */
+#define USBTMC_MIN_TIMEOUT	100
 /* Default USB timeout (in milliseconds) */
 #define USBTMC_TIMEOUT		5000
 
@@ -115,6 +117,7 @@ struct usbtmc_file_data {
 	struct usbtmc_device_data *data;
 	struct list_head file_elem;
 
+	u32            timeout;
 	u8             srq_byte;
 	atomic_t       srq_asserted;
 };
@@ -153,6 +156,8 @@ static int usbtmc_open(struct inode *inode, struct file *filp)
 	mutex_lock(&data->io_mutex);
 	file_data->data = data;
 
+	file_data->timeout = USBTMC_TIMEOUT;
+
 	INIT_LIST_HEAD(&file_data->file_elem);
 	spin_lock_irq(&data->dev_lock);
 	list_add_tail(&file_data->file_elem, &data->file_list);
@@ -460,7 +465,7 @@ static int usbtmc488_ioctl_read_stb(struct usbtmc_file_data *file_data,
 		rv = wait_event_interruptible_timeout(
 			data->waitq,
 			atomic_read(&data->iin_data_valid) != 0,
-			USBTMC_TIMEOUT);
+			file_data->timeout);
 		if (rv < 0) {
 			dev_dbg(dev, "wait interrupted %d\n", rv);
 			goto exit;
@@ -560,8 +565,10 @@ static int usbtmc488_ioctl_simple(struct usbtmc_device_data *data,
  *
  * Also updates bTag_last_write.
  */
-static int send_request_dev_dep_msg_in(struct usbtmc_device_data *data, size_t transfer_size)
+static int send_request_dev_dep_msg_in(struct usbtmc_file_data *file_data,
+				       size_t transfer_size)
 {
+	struct usbtmc_device_data *data = file_data->data;
 	int retval;
 	u8 *buffer;
 	int actual;
@@ -590,7 +597,8 @@ static int send_request_dev_dep_msg_in(struct usbtmc_device_data *data, size_t t
 	retval = usb_bulk_msg(data->usb_dev,
 			      usb_sndbulkpipe(data->usb_dev,
 					      data->bulk_out),
-			      buffer, USBTMC_HEADER_SIZE, &actual, USBTMC_TIMEOUT);
+			      buffer, USBTMC_HEADER_SIZE,
+			      &actual, file_data->timeout);
 
 	/* Store bTag (in case we need to abort) */
 	data->bTag_last_write = data->bTag;
@@ -640,7 +648,7 @@ static ssize_t usbtmc_read(struct file *filp, char __user *buf,
 
 	dev_dbg(dev, "usb_bulk_msg_in: count(%zu)\n", count);
 
-	retval = send_request_dev_dep_msg_in(data, count);
+	retval = send_request_dev_dep_msg_in(file_data, count);
 
 	if (retval < 0) {
 		if (data->auto_abort)
@@ -659,7 +667,7 @@ static ssize_t usbtmc_read(struct file *filp, char __user *buf,
 				      usb_rcvbulkpipe(data->usb_dev,
 						      data->bulk_in),
 				      buffer, USBTMC_SIZE_IOBUFFER, &actual,
-				      USBTMC_TIMEOUT);
+				      file_data->timeout);
 
 		dev_dbg(dev, "usb_bulk_msg: retval(%u), done(%zu), remaining(%zu), actual(%d)\n", retval, done, remaining, actual);
 
@@ -832,7 +840,7 @@ static ssize_t usbtmc_write(struct file *filp, const char __user *buf,
 					      usb_sndbulkpipe(data->usb_dev,
 							      data->bulk_out),
 					      buffer, n_bytes,
-					      &actual, USBTMC_TIMEOUT);
+					      &actual, file_data->timeout);
 			if (retval != 0)
 				break;
 			n_bytes -= actual;
@@ -1189,6 +1197,41 @@ exit:
 	return rv;
 }
 
+/*
+ * Get the usb timeout value
+ */
+static int usbtmc_ioctl_get_timeout(struct usbtmc_file_data *file_data,
+				void __user *arg)
+{
+	u32 timeout;
+
+	timeout = file_data->timeout;
+
+	return put_user(timeout, (__u32 __user *)arg);
+}
+
+/*
+ * Set the usb timeout value
+ */
+static int usbtmc_ioctl_set_timeout(struct usbtmc_file_data *file_data,
+				void __user *arg)
+{
+	u32 timeout;
+
+	if (get_user(timeout, (__u32 __user *)arg))
+		return -EFAULT;
+
+	/* Note that timeout = 0 means
+	 * MAX_SCHEDULE_TIMEOUT in usb_control_msg
+	 */
+	if (timeout < USBTMC_MIN_TIMEOUT)
+		return -EINVAL;
+
+	file_data->timeout = timeout;
+
+	return 0;
+}
+
 static long usbtmc_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
 	struct usbtmc_file_data *file_data;
@@ -1229,6 +1272,16 @@ static long usbtmc_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 		retval = usbtmc_ioctl_abort_bulk_in(data);
 		break;
 
+	case USBTMC_IOCTL_GET_TIMEOUT:
+		retval = usbtmc_ioctl_get_timeout(file_data,
+						  (void __user *)arg);
+		break;
+
+	case USBTMC_IOCTL_SET_TIMEOUT:
+		retval = usbtmc_ioctl_set_timeout(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

@@ -16,6 +16,8 @@
 #ifndef __LINUX_USB_TMC_H
 #define __LINUX_USB_TMC_H
 
+#include <linux/types.h>   /* __u8 etc */
+
 /* USB TMC status values */
 #define USBTMC_STATUS_SUCCESS				0x01
 #define USBTMC_STATUS_PENDING				0x02
@@ -46,6 +48,8 @@
 #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 USBTMC_IOCTL_GET_TIMEOUT	_IOR(USBTMC_IOC_NR, 9, __u32)
+#define USBTMC_IOCTL_SET_TIMEOUT	_IOW(USBTMC_IOC_NR, 10, __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)
 #define USBTMC488_IOCTL_REN_CONTROL	_IOW(USBTMC_IOC_NR, 19, unsigned char)