os/hid: Add os_hid_get_feature_timeout.

src/xrt/auxiliary/os/os_hid.h

@@ -38,6 +38,11 @@ struct os_hid_device
 	                   uint8_t *data,
 	                   size_t size);
 
+	int (*get_feature_timeout)(struct os_hid_device *hid_dev,
+	                           void *data,
+	                           size_t size,
+	                           uint32_t timeout);
+
 	int (*set_feature)(struct os_hid_device *hid_dev,
 	                   const uint8_t *data,
 	                   size_t size);
@@ -84,6 +89,18 @@ os_hid_get_feature(struct os_hid_device *hid_dev,
 	return hid_dev->get_feature(hid_dev, report_num, data, size);
 }
 
+/*!
+ * Get a feature report with a timeout.
+ */
+XRT_MAYBE_UNUSED static inline int
+os_hid_get_feature_timeout(struct os_hid_device *hid_dev,
+                           void *data,
+                           size_t size,
+                           uint32_t timeout)
+{
+	return hid_dev->get_feature_timeout(hid_dev, data, size, timeout);
+}
+
 /*!
  * Set a feature report.
  *

src/xrt/auxiliary/os/os_hid_hidraw.c

@@ -18,6 +18,7 @@
 #include <fcntl.h>
 #include <unistd.h>
 #include <string.h>
+#include <time.h>
 
 #include <sys/ioctl.h>
 
@@ -90,6 +91,31 @@ os_hidraw_get_feature(struct os_hid_device *ohdev,
 	return ioctl(hrdev->fd, HIDIOCGFEATURE(length), data);
 }
 
+static int
+os_hidraw_get_feature_timeout(struct os_hid_device *ohdev,
+                              void *data,
+                              size_t length,
+                              uint32_t timeout)
+{
+	struct hid_hidraw *hrdev = (struct hid_hidraw *)ohdev;
+
+	struct timespec ts = {.tv_sec = 0, .tv_nsec = 1000000};
+	unsigned int i;
+	int ret = 0;
+
+	for (i = 0; i < timeout; i++) {
+		ret = ioctl(hrdev->fd, HIDIOCGFEATURE(length), data);
+		if (ret != -1 || errno != EPIPE)
+			break;
+
+		ts.tv_sec = 0;
+		ts.tv_nsec = 1000000;
+		nanosleep(&ts, NULL);
+	}
+
+	return ret;
+}
+
 static int
 os_hidraw_set_feature(struct os_hid_device *ohdev,
                       const uint8_t *data,
@@ -117,6 +143,7 @@ os_hid_open_hidraw(const char *path, struct os_hid_device **out_hid)
 	hrdev->base.read = os_hidraw_read;
 	hrdev->base.write = os_hidraw_write;
 	hrdev->base.get_feature = os_hidraw_get_feature;
+	hrdev->base.get_feature_timeout = os_hidraw_get_feature_timeout;
 	hrdev->base.set_feature = os_hidraw_set_feature;
 	hrdev->base.destroy = os_hidraw_destroy;
 	hrdev->fd = open(path, O_RDWR);