usb: usbtmc: Add support for missing functions in USBTMC-USB488 spec

Background:
When performing a read on an instrument that is executing a function that runs longer than the USB timeout the instrument may hang and require a device reset to recover. The READ_STATUS_BYTE operation always returns even when the instrument is busy permitting to poll for the appropriate condition. This capability is refered to in instrument application notes on synchronizing acquisitions for other platforms.

Signed-off-by Dave Penkler <[email protected]>

---
 drivers/usb/class/usbtmc.c   | 223 +++++++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/usb/tmc.h |   2 +
 2 files changed, 225 insertions(+)

drivers/usb/class/usbtmc.c +223 -0

index 7a11a82..c1593e7 100644
@@ -87,6 +87,20 @@ struct usbtmc_device_data {
        u8 bTag_last_write;     /* needed for abort */
        u8 bTag_last_read;      /* needed for abort */
 
+
+       /* data for interrupt in endpoint handling */
+       u8             bNotify1;
+       u8             bNotify2;
+       u16            ifnum;
+       u8             iin_bTag;
+       u8            *iin_buffer;
+       atomic_t       iin_data_valid;
+       unsigned int   iin_ep;
+       int            iin_ep_present;
+       int            iin_interval;
+       struct urb    *iin_urb;
+       u16            iin_wMaxPacketSize;
+
        u8 rigol_quirk;
 
        /* attributes from the USB TMC spec for this device */

@@ -99,6 +113,7 @@ struct usbtmc_device_data {
        struct usbtmc_dev_capabilities  capabilities;
        struct kref kref;
        struct mutex io_mutex;  /* only one i/o function running at a time */
+       wait_queue_head_t waitq;
 };
 #define to_usbtmc_data(d) container_of(d, struct usbtmc_device_data, kref)
 

@@ -373,6 +388,91 @@ exit:
        return rv;
 }
 
+static int usbtmc488_ioctl_read_stb(struct usbtmc_device_data *data,
+                               unsigned long arg)
+{
+       u8 *buffer;
+       struct device *dev;
+       int rv;
+       u8 tag, stb;
+
+       dev = &data->intf->dev;
+
+       dev_dbg(dev, "Enter ioctl_read_stb iin_ep_present: %d\n",
+               data->iin_ep_present);
+
+       buffer = kmalloc(8, GFP_KERNEL);
+       if (!buffer)
+               return -ENOMEM;
+
+
+       atomic_set(&data->iin_data_valid, 0);
+
+       rv = usb_control_msg(data->usb_dev,
+                       usb_rcvctrlpipe(data->usb_dev, 0),
+                       USBTMC488_REQUEST_READ_STATUS_BYTE,
+                       USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE,
+                       data->iin_bTag,
+                       data->ifnum,
+                       buffer, 0x03, USBTMC_TIMEOUT);
+
+       if (rv < 0) {
+               dev_err(dev, "stb usb_control_msg returned %d\n", rv);
+               goto exit;
+       }
+
+       if (buffer[0] != USBTMC_STATUS_SUCCESS) {
+               dev_err(dev, "control status returned %x\n",
+                       buffer[0]);
+               rv = -EIO;
+               goto exit;
+       }
+
+       if (data->iin_ep_present) {
+
+               rv = wait_event_interruptible_timeout(
+                       data->waitq,
+                       (atomic_read(&data->iin_data_valid) != 0),
+                       USBTMC_TIMEOUT
+                       );
+
+               if (rv < 0) {
+                       dev_dbg(dev, "wait interrupted %d\n", rv);
+                       goto exit;
+               }
+
+               if (rv == 0) {
+                       dev_dbg(dev, "wait timed out\n");
+                       rv = -ETIME;
+                       goto exit;
+               }
+
+               tag = data->bNotify1 & 0x7f;
+
+               if (tag != data->iin_bTag) {
+                       dev_err(dev, "expected bTag %x got %x\n",
+                               data->iin_bTag, tag);
+               }
+
+               stb = data->bNotify2;
+       } else {
+               stb = buffer[2];
+       }
+
+       rv = copy_to_user((void __user *)arg, &stb, sizeof(stb));
+       if (rv)
+               rv = -EFAULT;
+
+ exit:
+       /* bump interrupt bTag */
+       data->iin_bTag += 1;
+       if (data->iin_bTag > 127)
+               data->iin_bTag = 2;
+
+       kfree(buffer);
+       return rv;
+}
+
 /*
  * Sends a REQUEST_DEV_DEP_MSG_IN message on the Bulk-IN endpoint.
  * @transfer_size: number of bytes to request from the device.

@@ -1069,6 +1169,11 @@ static long usbtmc_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
        case USBTMC_IOCTL_ABORT_BULK_IN:
                retval = usbtmc_ioctl_abort_bulk_in(data);
                break;
+
+       case USBTMC488_IOCTL_READ_STB:
+               retval = usbtmc488_ioctl_read_stb(data, arg);
+               break;
+
        }
 
 skip_io_on_zombie:

@@ -1092,6 +1197,69 @@ static struct usb_class_driver usbtmc_class = {
        .minor_base =   USBTMC_MINOR_BASE,
 };
 
+static void usbtmc_interrupt(struct urb *urb)
+{
+       struct usbtmc_device_data *data = urb->context;
+       int status = urb->status;
+       int rv;
+
+       dev_dbg(&data->intf->dev, "int status: %d len %d\n",
+               status, urb->actual_length);
+
+       switch (status) {
+       case 0: /* SUCCESS */
+
+               if (data->iin_buffer[0] & 0x80) {
+                       /* check for valid STB notification */
+                       if ((data->iin_buffer[0] & 0x7f) > 1) {
+                               data->bNotify1 = data->iin_buffer[0];
+                               data->bNotify2 = data->iin_buffer[1];
+                               atomic_set(&data->iin_data_valid, 1);
+                               wake_up_interruptible(&data->waitq);
+                               goto exit;
+                       }
+               }
+               dev_warn(&data->intf->dev, "invalid notification: %x\n",
+                       data->iin_buffer[0]);
+               break;
+       case -EOVERFLOW:
+               dev_err(&data->intf->dev,
+                       "%s - overflow with length %d, actual length is %d\n",
+                       __func__, data->iin_wMaxPacketSize, urb->actual_length);
+       case -ECONNRESET:
+       case -ENOENT:
+       case -ESHUTDOWN:
+       case -EILSEQ:
+       case -ETIME:
+               /* urb terminated, clean up */
+               dev_dbg(&data->intf->dev,
+                       "%s - urb terminated, status: %d\n",
+                       __func__, status);
+               return;
+       default:
+               dev_err(&data->intf->dev,
+                       "%s - unknown status received: %d\n",
+                       __func__, status);
+       }
+exit:
+       rv = usb_submit_urb(urb, GFP_ATOMIC);
+       if (rv) {
+               dev_err(&data->intf->dev, "%s - usb_submit_urb failed: %d\n",
+                       __func__, rv);
+       }
+}
+
+static void usbtmc_free_int(struct usbtmc_device_data *data)
+{
+       if (data->iin_ep_present) {
+               if (data->iin_urb) {
+                       usb_kill_urb(data->iin_urb);
+                       kfree(data->iin_buffer);
+                       usb_free_urb(data->iin_urb);
+                       kref_put(&data->kref, usbtmc_delete);
+               }
+       }
+}
 
 static int usbtmc_probe(struct usb_interface *intf,
                        const struct usb_device_id *id)

@@ -1114,6 +1282,8 @@ static int usbtmc_probe(struct usb_interface *intf,
        usb_set_intfdata(intf, data);
        kref_init(&data->kref);
        mutex_init(&data->io_mutex);
+       init_waitqueue_head(&data->waitq);
+       atomic_set(&data->iin_data_valid, 0);
        data->zombie = 0;
 
        /* Determine if it is a Rigol or not */

@@ -1134,9 +1304,12 @@ static int usbtmc_probe(struct usb_interface *intf,
        data->bTag      = 1;
        data->TermCharEnabled = 0;
        data->TermChar = '\n';
+       /*  2 <= bTag <= 127   USBTMC-USB488 subclass specification 4.3.1 */
+       data->iin_bTag = 2;
 
        /* USBTMC devices have only one setting, so use that */
        iface_desc = data->intf->cur_altsetting;
+       data->ifnum = iface_desc->desc.bInterfaceNumber;
 
        /* Find bulk in endpoint */
        for (n = 0; n < iface_desc->desc.bNumEndpoints; n++) {

@@ -1161,6 +1334,20 @@ static int usbtmc_probe(struct usb_interface *intf,
                        break;
                }
        }
+       /* Find int endpoint */
+       for (n = 0; n < iface_desc->desc.bNumEndpoints; n++) {
+               endpoint = &iface_desc->endpoint[n].desc;
+
+               if (usb_endpoint_is_int_in(endpoint)) {
+                       data->iin_ep_present = 1;
+                       data->iin_ep = endpoint->bEndpointAddress;
+                       data->iin_wMaxPacketSize = usb_endpoint_maxp(endpoint);
+                       data->iin_interval = endpoint->bInterval;
+                       dev_dbg(&intf->dev, "Found Int in endpoint at %u\n",
+                               data->iin_ep);
+                       break;
+               }
+       }
 
        retcode = get_capabilities(data);
        if (retcode)

@@ -1169,6 +1356,40 @@ static int usbtmc_probe(struct usb_interface *intf,
                retcode = sysfs_create_group(&intf->dev.kobj,
                                             &capability_attr_grp);
 
+
+       if (data->iin_ep_present) {
+               /* allocate int urb */
+               data->iin_urb = usb_alloc_urb(0, GFP_KERNEL);
+               if (!data->iin_urb) {
+                       dev_err(&intf->dev, "Failed to allocate int urb\n");
+                       goto error_register;
+               }
+
+               /* will reference data in int urb */
+               kref_get(&data->kref);
+
+               /* allocate buffer for interrupt in */
+               data->iin_buffer = kmalloc(data->iin_wMaxPacketSize,
+                                       GFP_KERNEL);
+               if (!data->iin_buffer) {
+                       dev_err(&intf->dev, "Failed to allocate int buf\n");
+                       goto error_register;
+               }
+
+               /* fill interrupt urb */
+               usb_fill_int_urb(data->iin_urb, data->usb_dev,
+                               usb_rcvintpipe(data->usb_dev, data->iin_ep),
+                               data->iin_buffer, data->iin_wMaxPacketSize,
+                               usbtmc_interrupt,
+                               data, data->iin_interval);
+
+               if (usb_submit_urb(data->iin_urb, GFP_KERNEL)) {
+                       retcode = -EIO;
+                       dev_err(&intf->dev, "Failed to submit iin_urb\n");
+                       goto error_register;
+               }
+       }
+
        retcode = sysfs_create_group(&intf->dev.kobj, &data_attr_grp);
 
        retcode = usb_register_dev(intf, &usbtmc_class);

@@ -1185,6 +1406,7 @@ static int usbtmc_probe(struct usb_interface *intf,
 error_register:
        sysfs_remove_group(&intf->dev.kobj, &capability_attr_grp);
        sysfs_remove_group(&intf->dev.kobj, &data_attr_grp);
+       usbtmc_free_int(data);
        kref_put(&data->kref, usbtmc_delete);
        return retcode;
 }

@@ -1196,6 +1418,7 @@ static void usbtmc_disconnect(struct usb_interface *intf)
        dev_dbg(&intf->dev, "usbtmc_disconnect called\n");
 
        data = usb_get_intfdata(intf);
+       usbtmc_free_int(data);
        usb_deregister_dev(intf, &usbtmc_class);
        sysfs_remove_group(&intf->dev.kobj, &capability_attr_grp);
        sysfs_remove_group(&intf->dev.kobj, &data_attr_grp);

include/uapi/linux/usb/tmc.h +2 -1

index c045ae1..49060ea 100644
@@ -30,6 +30,7 @@
 #define USBTMC_REQUEST_CHECK_CLEAR_STATUS              6
 #define USBTMC_REQUEST_GET_CAPABILITIES                        7
 #define USBTMC_REQUEST_INDICATOR_PULSE                 64
+#define USBTMC488_REQUEST_READ_STATUS_BYTE              128
 
 /* Request values for USBTMC driver's ioctl entry point */
 #define USBTMC_IOC_NR                  91

@@ -39,5 +40,6 @@
 #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 USBTMC488_IOCTL_READ_STB       _IOR(USBTMC_IOC_NR, 18, unsigned char)
 
 #endif
--

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Background:
In many situations operations on multiple instruments need to be synchronized. poll/select provide a convenient way of waiting on a number of different instruments and other peripherals simultaneously.

Signed-off-by Dave Penkler <[email protected]>

---
 drivers/usb/class/usbtmc.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

drivers/usb/class/usbtmc.c +1 -0

index 2239cd0..bb9a6ab 100644
@@ -27,6 +27,7 @@
 #include <linux/uaccess.h>
 #include <linux/kref.h>
 #include <linux/slab.h>
+#include <linux/poll.h>
 #include <linux/mutex.h>
 #include <linux/usb.h>
 #include <linux/usb/tmc.h>

drivers/usb/class/usbtmc.c +18 -1

+
+       mutex_lock(&data->io_mutex);
+
+       if (data->zombie) {
+               mask = POLLHUP | POLLERR;
+               goto no_poll;
+       }
+
+       poll_wait(file, &data->waitq, wait);
+
+       mask = (atomic_read(&data->srq_asserted)) ? POLLIN | POLLRDNORM : 0;
+
+no_poll:
+       mutex_unlock(&data->io_mutex);
+       return mask;
+}
+
 static const struct file_operations fops = {
        .owner          = THIS_MODULE,
        .read           = usbtmc_read,

@@ -1201,6 +1223,7 @@ static const struct file_operations fops = {
        .release        = usbtmc_release,
        .unlocked_ioctl = usbtmc_ioctl,
        .fasync         = usbtmc_fasync,
+       .poll           = usbtmc_poll,
        .llseek         = default_llseek,
 };
 
--

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This is a convenience function to obtain an instrument's capabilities from its file descriptor without having to access sysfs from the user program.

Signed-off-by Dave Penkler <[email protected]>

---
 drivers/usb/class/usbtmc.c   | 12 ++++++++++++
 include/uapi/linux/usb/tmc.h | 21 ++++++++++++++++++---
 2 files changed, 30 insertions(+), 3 deletions(-)

drivers/usb/class/usbtmc.c +12 -0

index bb9a6ab..deca4b5 100644
@@ -103,6 +103,9 @@ struct usbtmc_device_data {
        u16            iin_wMaxPacketSize;
        atomic_t       srq_asserted;
 
+       /* coalesced usb488_caps from usbtmc_dev_capabilities */
+       u8 usb488_caps;
+
        u8 rigol_quirk;
 
        /* attributes from the USB TMC spec for this device */

@@ -1001,6 +1004,7 @@ static int get_capabilities(struct usbtmc_device_data *data)
        data->capabilities.device_capabilities = buffer[5];
        data->capabilities.usb488_interface_capabilities = buffer[14];
        data->capabilities.usb488_device_capabilities = buffer[15];
+       data->usb488_caps = (buffer[14] & 0x07) | ((buffer[15] & 0x0f) << 4);
        rv = 0;
 
 err_out:

@@ -1176,6 +1180,14 @@ static long usbtmc_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
                retval = usbtmc_ioctl_abort_bulk_in(data);
                break;
 
+       case USBTMC488_IOCTL_GET_CAPS:
+               retval = copy_to_user((void __user *)arg,
+                               &data->usb488_caps,
+                               sizeof(data->usb488_caps));
+               if (retval)
+                       retval = -EFAULT;
+               break;
+
        case USBTMC488_IOCTL_READ_STB:
                retval = usbtmc488_ioctl_read_stb(data, arg);
                break;

include/uapi/linux/usb/tmc.h +1 -0

index 49060ea..2606664 100644
@@ -2,12 +2,14 @@
  * Copyright (C) 2007 Stefan Kopp, Gechingen, Germany
  * Copyright (C) 2008 Novell, Inc.
  * Copyright (C) 2008 Greg Kroah-Hartman <[email protected]>
+ * Copyright (C) 2015 Dave Penkler <[email protected]>
  *

include/uapi/linux/usb/tmc.h +0 -0

  */
 

#ifndef __LINUX_USB_TMC_H

include/uapi/linux/usb/tmc.h +13 -1

@@ -40,6 +42,19 @@
 #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 USBTMC488_IOCTL_GET_CAPS       _IO(USBTMC_IOC_NR, 17)
 #define USBTMC488_IOCTL_READ_STB       _IOR(USBTMC_IOC_NR, 18, unsigned char)
 
+/* Driver encoded usb488 capabilities */
+#define USBTMC488_CAPABILITY_TRIGGER         1
+#define USBTMC488_CAPABILITY_SIMPLE          2
+#define USBTMC488_CAPABILITY_REN_CONTROL     2
+#define USBTMC488_CAPABILITY_GOTO_LOCAL      2
+#define USBTMC488_CAPABILITY_LOCAL_LOCKOUT   2
+#define USBTMC488_CAPABILITY_488_DOT_2       4
+#define USBTMC488_CAPABILITY_DT1             16
+#define USBTMC488_CAPABILITY_RL1             32
+#define USBTMC488_CAPABILITY_SR1             64
+#define USBTMC488_CAPABILITY_FULL_SCPI       128
+
 #endif
--

2.5.1
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These ioctls provide support for the USBTMC-USB488 control requests for REN_CONTROL, GO_TO_LOCAL and LOCAL_LOCKOUT

Signed-off-by Dave Penkler <[email protected]>

---
 drivers/usb/class/usbtmc.c   | 76 ++++++++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/usb/tmc.h |  9 +++++-
 2 files changed, 84 insertions(+), 1 deletion(-)

drivers/usb/class/usbtmc.c +3 -0

index deca4b5..646bfff 100644
@@ -482,6 +482,68 @@ static int usbtmc488_ioctl_read_stb(struct usbtmc_device_data *data,
        return rv;
 }
 
+static int usbtmc488_ioctl_simple(struct usbtmc_device_data *data,
+                               unsigned long arg,
+                               unsigned int cmd)

drivers/usb/class/usbtmc.c +49 -0

+       } else {
+               wValue = 0;
+       }
+
+       rv = usb_control_msg(data->usb_dev,
+                       usb_rcvctrlpipe(data->usb_dev, 0),
+                       cmd,
+                       USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE,
+                       wValue,
+                       data->ifnum,
+                       buffer, 0x01, USBTMC_TIMEOUT);
+
+       if (rv < 0) {
+               dev_err(dev, "simple usb_control_msg failed %d\n", rv);
+               goto exit;
+       } else if (rv != 1) {
+               dev_warn(dev, "simple usb_control_msg returned %d\n", rv);
+               rv = -EIO;
+               goto exit;
+       }
+
+       if (buffer[0] != USBTMC_STATUS_SUCCESS) {
+               dev_err(dev, "simple control status returned %x\n",
+                       buffer[0]);
+               rv = -EIO;
+               goto exit;
+       } else {
+               rv = 0;
+       }
+
+ exit:
+       kfree(buffer);
+       return rv;
+}
+
 /*
  * Sends a REQUEST_DEV_DEP_MSG_IN message on the Bulk-IN endpoint.
  * @transfer_size: number of bytes to request from the device.

@@ -1192,6 +1254,20 @@ static long usbtmc_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
                retval = usbtmc488_ioctl_read_stb(data, arg);
                break;
 
+       case USBTMC488_IOCTL_REN_CONTROL:
+               retval = usbtmc488_ioctl_simple(data, arg,
+                                               USBTMC488_REQUEST_REN_CONTROL);
+               break;
+
+       case USBTMC488_IOCTL_GOTO_LOCAL:
+               retval = usbtmc488_ioctl_simple(data, arg,
+                                               USBTMC488_REQUEST_GOTO_LOCAL);
+               break;
+
+       case USBTMC488_IOCTL_LOCAL_LOCKOUT:
+               retval = usbtmc488_ioctl_simple(data, arg,
+                                               USBTMC488_REQUEST_LOCAL_LOCKOUT);
+               break;
        }
 
 skip_io_on_zombie:

include/uapi/linux/usb/tmc.h +8 -2

index 2606664..fe9663f 100644
@@ -1,3 +1,4 @@
+
 /*
  * Copyright (C) 2007 Stefan Kopp, Gechingen, Germany
  * Copyright (C) 2008 Novell, Inc.

@@ -32,7 +33,10 @@
 #define USBTMC_REQUEST_CHECK_CLEAR_STATUS              6
 #define USBTMC_REQUEST_GET_CAPABILITIES                        7
 #define USBTMC_REQUEST_INDICATOR_PULSE                 64
-#define USBTMC488_REQUEST_READ_STATUS_BYTE              128
+#define USBTMC488_REQUEST_READ_STATUS_BYTE             128
+#define USBTMC488_REQUEST_REN_CONTROL                  160
+#define USBTMC488_REQUEST_GOTO_LOCAL                   161
+#define USBTMC488_REQUEST_LOCAL_LOCKOUT                        162
 
 /* Request values for USBTMC driver's ioctl entry point */
 #define USBTMC_IOC_NR                  91

@@ -44,6 +48,9 @@
 #define USBTMC_IOCTL_CLEAR_IN_HALT     _IO(USBTMC_IOC_NR, 7)
 #define USBTMC488_IOCTL_GET_CAPS       _IO(USBTMC_IOC_NR, 17)
 #define USBTMC488_IOCTL_READ_STB       _IOR(USBTMC_IOC_NR, 18, unsigned char)
+#define USBTMC488_IOCTL_REN_CONTROL    _IOW(USBTMC_IOC_NR, 19, unsigned char)
+#define USBTMC488_IOCTL_GOTO_LOCAL     _IO(USBTMC_IOC_NR, 20)
+#define USBTMC488_IOCTL_LOCAL_LOCKOUT  _IO(USBTMC_IOC_NR, 21)
 
 /* Driver encoded usb488 capabilities */
 #define USBTMC488_CAPABILITY_TRIGGER         1
--

2.5.1
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Quoted 6 lines

Background:
When performing a read on an instrument that is executing a function that runs longer than the USB timeout the instrument may hang and require a device reset to recover. The READ_STATUS_BYTE operation always returns even when the instrument is busy permitting to poll for the appropriate condition. This capability is refered to in instrument application notes

Quoted 1 line

on synchronizing acquisitions for other platforms.

Won't comment precisely by line, but common nitpicks about style:
- added empty lines where no need
- redundant parens
- pieces of code takes whole line when they are quite fit tail of previous one.

And why malloc for 8 bytes?

Quoted 1 line

Signed-off-by Dave Penkler <[email protected]>

Quoted 6 lines · Andy Shevchenko

Won't comment precisely by line, but common nitpicks about style:
- added empty lines where no need
- redundant parens
- pieces of code takes whole line when they are quite fit tail of
previous one.

Quoted 1 line

And why malloc for 8 bytes?

It's a good tone to skip the parts you're not commenting on, so others
wouldn't have to scroll in vain.

Quoted 8 lines · Dave Penkler

Background:
When performing a read on an instrument that is executing a function that runs longer than the USB timeout the instrument may hang and require a device reset to recover. The READ_STATUS_BYTE operation always returns even when the instrument is busy permitting to poll for the appropriate condition. This capability is refered to in instrument application notes on synchronizing acquisitions for other platforms.

Won't comment precisely by line, but common nitpicks about style:
- added empty lines where no need
- redundant parens
- pieces of code takes whole line when they are quite fit tail of previous one.

And why malloc for 8 bytes?

Thanks for your comments, I will resubmit taking into account all suggestions.

Quoted 1 line

Quoted 1 line

- redundant parens

Quoted 3 lines

Quoted 3 lines

- pieces of code takes whole line when they are quite fit tail of
previous one.

I have endeavoured to follow the coding style of the original driver and stick to the kernel coding-style guidelines.
Please point to the specific locations where I have failed to do so.

Quoted 2 lines · Dave Penkler

These ioctls provide support for the USBTMC-USB488 control requests for REN_CONTROL, GO_TO_LOCAL and LOCAL_LOCKOUT

drivers/usb/class/usbtmc.c static int usbtmc488_ioctl_read_stb(struct usbtmc_device_data *data, · line 511

Quoted 3 lines

drivers/usb/class/usbtmc.c +3 -0

+                       goto exit;
+               }
+               wValue = (val) ? 1 : 0;

!!val;