[09/12] usb: usbtmc: Fix ioctl USBTMC_IOCTL_CLEAR

Commit Message

Guido Kiener May 17, 2018, 5:03 p.m. UTC

Insert a sleep of 50 ms between subsequent CHECK_CLEAR_STATUS
control requests to avoid stressing the instrument with repeated
requests.

Some instruments need time to cleanup internal I/O buffers.
Polling and repeated requests slow down the response time of
devices.

Signed-off-by: Guido Kiener <[e-mail]>
Reviewed-by: Steve Bayless <[e-mail]>
---
 drivers/usb/class/usbtmc.c | 46 +++++++++++++++-----------------------
 1 file changed, 18 insertions(+), 28 deletions(-)

Comments

Oliver Neukum May 23, 2018, 12:10 p.m. UTC | #1

Am Donnerstag, den 17.05.2018, 19:03 +0200 schrieb Guido Kiener:
> Insert a sleep of 50 ms between subsequent CHECK_CLEAR_STATUS
> control requests to avoid stressing the instrument with repeated
> requests.
> 
> Some instruments need time to cleanup internal I/O buffers.
> Polling and repeated requests slow down the response time of
> devices.

The connection between the patch and the description is loose.

	Regards
		Oliver

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Patch

diff --git a/drivers/usb/class/usbtmc.c b/drivers/usb/class/usbtmc.c
index 76b0a7b083a7..165b707991f3 100644
--- a/drivers/usb/class/usbtmc.c
+++ b/drivers/usb/class/usbtmc.c
@@ -1643,20 +1643,17 @@  static ssize_t usbtmc_write(struct file *filp, const char __user *buf,
 
 static int usbtmc_ioctl_clear(struct usbtmc_device_data *data)
 {
-	struct usb_host_interface *current_setting;
-	struct usb_endpoint_descriptor *desc;
 	struct device *dev;
 	u8 *buffer;
 	int rv;
 	int n;
 	int actual = 0;
-	int max_size;
 
 	dev = &data->intf->dev;
 
 	dev_dbg(dev, "Sending INITIATE_CLEAR request\n");
 
-	buffer = kmalloc(USBTMC_SIZE_IOBUFFER, GFP_KERNEL);
+	buffer = kmalloc(USBTMC_BUFSIZE, GFP_KERNEL);
 	if (!buffer)
 		return -ENOMEM;
 
@@ -1664,7 +1661,7 @@  static int usbtmc_ioctl_clear(struct usbtmc_device_data *data)
 			     usb_rcvctrlpipe(data->usb_dev, 0),
 			     USBTMC_REQUEST_INITIATE_CLEAR,
 			     USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE,
-			     0, 0, buffer, 1, USBTMC_TIMEOUT);
+			     0, 0, buffer, 1, USB_CTRL_GET_TIMEOUT);
 	if (rv < 0) {
 		dev_err(dev, "usb_control_msg returned %d\n", rv);
 		goto exit;
@@ -1678,22 +1675,6 @@  static int usbtmc_ioctl_clear(struct usbtmc_device_data *data)
 		goto exit;
 	}
 
-	max_size = 0;
-	current_setting = data->intf->cur_altsetting;
-	for (n = 0; n < current_setting->desc.bNumEndpoints; n++) {
-		desc = &current_setting->endpoint[n].desc;
-		if (desc->bEndpointAddress == data->bulk_in)
-			max_size = usb_endpoint_maxp(desc);
-	}
-
-	if (max_size == 0) {
-		dev_err(dev, "Couldn't get wMaxPacketSize\n");
-		rv = -EPERM;
-		goto exit;
-	}
-
-	dev_dbg(dev, "wMaxPacketSize is %d\n", max_size);
-
 	n = 0;
 
 usbtmc_clear_check_status:
@@ -1704,7 +1685,7 @@  static int usbtmc_ioctl_clear(struct usbtmc_device_data *data)
 			     usb_rcvctrlpipe(data->usb_dev, 0),
 			     USBTMC_REQUEST_CHECK_CLEAR_STATUS,
 			     USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE,
-			     0, 0, buffer, 2, USBTMC_TIMEOUT);
+			     0, 0, buffer, 2, USB_CTRL_GET_TIMEOUT);
 	if (rv < 0) {
 		dev_err(dev, "usb_control_msg returned %d\n", rv);
 		goto exit;
@@ -1721,15 +1702,19 @@  static int usbtmc_ioctl_clear(struct usbtmc_device_data *data)
 		goto exit;
 	}
 
-	if (buffer[1] == 1)
+	if ((buffer[1] & 1) != 0) {
 		do {
 			dev_dbg(dev, "Reading from bulk in EP\n");
 
 			rv = usb_bulk_msg(data->usb_dev,
 					  usb_rcvbulkpipe(data->usb_dev,
 							  data->bulk_in),
-					  buffer, USBTMC_SIZE_IOBUFFER,
-					  &actual, USBTMC_TIMEOUT);
+					  buffer, USBTMC_BUFSIZE,
+					  &actual, USB_CTRL_GET_TIMEOUT);
+
+			print_hex_dump_debug("usbtmc ", DUMP_PREFIX_NONE,
+					     16, 1, buffer, actual, true);
+
 			n++;
 
 			if (rv < 0) {
@@ -1737,10 +1722,15 @@  static int usbtmc_ioctl_clear(struct usbtmc_device_data *data)
 					rv);
 				goto exit;
 			}
-		} while ((actual == max_size) &&
+		} while ((actual == USBTMC_BUFSIZE) &&
 			  (n < USBTMC_MAX_READS_TO_CLEAR_BULK_IN));
+	} else {
+		/* do not stress device with subsequent requests */
+		msleep(50);
+		n++;
+	}
 
-	if (actual == max_size) {
+	if (n >= USBTMC_MAX_READS_TO_CLEAR_BULK_IN) {
 		dev_err(dev, "Couldn't clear device buffer within %d cycles\n",
 			USBTMC_MAX_READS_TO_CLEAR_BULK_IN);
 		rv = -EPERM;
@@ -1754,7 +1744,7 @@  static int usbtmc_ioctl_clear(struct usbtmc_device_data *data)
 	rv = usb_clear_halt(data->usb_dev,
 			    usb_sndbulkpipe(data->usb_dev, data->bulk_out));
 	if (rv < 0) {
-		dev_err(dev, "usb_control_msg returned %d\n", rv);
+		dev_err(dev, "usb_clear_halt returned %d\n", rv);
 		goto exit;
 	}
 	rv = 0;