Wait until an SRQ (service request) is received on the interrupt pipe
or until the given period of time is expired. In contrast to the
poll() function this ioctl does not return when other (a)synchronous
I/O operations fail with EPOLLERR.

Signed-off-by: Guido Kiener <guido.kie...@rohde-schwarz.com>
Reviewed-by: Steve Bayless <steve_bayl...@keysight.com>
---
 drivers/usb/class/usbtmc.c   | 60 ++++++++++++++++++++++++++++++++++--
 include/uapi/linux/usb/tmc.h |  1 +
 2 files changed, 59 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/class/usbtmc.c b/drivers/usb/class/usbtmc.c
index de664a345e69..6b8b8510cfc4 100644
--- a/drivers/usb/class/usbtmc.c
+++ b/drivers/usb/class/usbtmc.c
@@ -594,6 +594,54 @@ static int usbtmc488_ioctl_read_stb(struct 
usbtmc_file_data *file_data,
        return rv;
 }
 
+static int usbtmc488_ioctl_wait_srq(struct usbtmc_file_data *file_data,
+                                   unsigned int __user *arg)
+{
+       struct usbtmc_device_data *data = file_data->data;
+       struct device *dev = &data->intf->dev;
+       int rv;
+       unsigned int timeout;
+       unsigned long expire;
+
+       if (!data->iin_ep_present) {
+               dev_dbg(dev, "no interrupt endpoint present\n");
+               return -EFAULT;
+       }
+
+       if (get_user(timeout, arg))
+               return -EFAULT;
+
+       expire = msecs_to_jiffies(timeout);
+
+       mutex_unlock(&data->io_mutex);
+
+       rv = wait_event_interruptible_timeout(
+                       data->waitq,
+                       atomic_read(&file_data->srq_asserted) != 0 ||
+                       atomic_read(&file_data->closing),
+                       expire);
+
+       mutex_lock(&data->io_mutex);
+
+       /* Note! disconnect or close could be called in the meantime */
+       if (atomic_read(&file_data->closing) || data->zombie)
+               rv = -ENODEV;
+
+       if (rv < 0) {
+               /* dev can be invalid now! */
+               pr_debug("%s - wait interrupted %d\n", __func__, rv);
+               return rv;
+       }
+
+       if (rv == 0) {
+               dev_dbg(dev, "%s - wait timed out\n", __func__);
+               return -ETIMEDOUT;
+       }
+
+       dev_dbg(dev, "%s - srq asserted\n", __func__);
+       return 0;
+}
+
 static int usbtmc488_ioctl_simple(struct usbtmc_device_data *data,
                                void __user *arg, unsigned int cmd)
 {
@@ -2149,6 +2197,11 @@ static long usbtmc_ioctl(struct file *file, unsigned int 
cmd, unsigned long arg)
                retval = usbtmc488_ioctl_trigger(file_data);
                break;
 
+       case USBTMC488_IOCTL_WAIT_SRQ:
+               retval = usbtmc488_ioctl_wait_srq(file_data,
+                                                 (unsigned int __user *)arg);
+               break;
+
        case USBTMC_IOCTL_CANCEL_IO:
                retval = usbtmc_ioctl_cancel_io(file_data);
                break;
@@ -2290,6 +2343,7 @@ static void usbtmc_interrupt(struct urb *urb)
        case -ESHUTDOWN:
        case -EILSEQ:
        case -ETIME:
+       case -EPIPE:
                /* urb terminated, clean up */
                dev_dbg(dev, "urb terminated, status: %d\n", status);
                return;
@@ -2308,7 +2362,9 @@ static void usbtmc_free_int(struct usbtmc_device_data 
*data)
                return;
        usb_kill_urb(data->iin_urb);
        kfree(data->iin_buffer);
+       data->iin_buffer = NULL;
        usb_free_urb(data->iin_urb);
+       data->iin_urb = NULL;
        kref_put(&data->kref, usbtmc_delete);
 }
 
@@ -2420,8 +2476,8 @@ static int usbtmc_probe(struct usb_interface *intf,
 
        retcode = usb_register_dev(intf, &usbtmc_class);
        if (retcode) {
-               dev_err(&intf->dev, "Not able to get a minor"
-                       " (base %u, slice default): %d\n", USBTMC_MINOR_BASE,
+               dev_err(&intf->dev, "Not able to get a minor (base %u, slice 
default): %d\n",
+                       USBTMC_MINOR_BASE,
                        retcode);
                goto error_register;
        }
diff --git a/include/uapi/linux/usb/tmc.h b/include/uapi/linux/usb/tmc.h
index 1540716de293..35b63530121d 100644
--- a/include/uapi/linux/usb/tmc.h
+++ b/include/uapi/linux/usb/tmc.h
@@ -96,6 +96,7 @@ struct usbtmc_message {
 #define USBTMC488_IOCTL_GOTO_LOCAL     _IO(USBTMC_IOC_NR, 20)
 #define USBTMC488_IOCTL_LOCAL_LOCKOUT  _IO(USBTMC_IOC_NR, 21)
 #define USBTMC488_IOCTL_TRIGGER                _IO(USBTMC_IOC_NR, 22)
+#define USBTMC488_IOCTL_WAIT_SRQ       _IOW(USBTMC_IOC_NR, 23, unsigned int)
 
 /* Cancel and cleanup asynchronous calls */
 #define USBTMC_IOCTL_CANCEL_IO         _IO(USBTMC_IOC_NR, 35)
-- 
2.17.0

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