/sys/bus/pci/devices doesn't exist as kms-drm exports sysfs via sysctl

  $ clinfo | fgrep clock
    Max clock frequency                             0MHz

--- shared/source/os_interface/linux/drm_neo.cpp.orig	2020-04-11 07:41:07 UTC
+++ shared/source/os_interface/linux/drm_neo.cpp
@@ -24,6 +24,13 @@
 #include <fstream>
 #include <linux/limits.h>
 
+#if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
+#include <sys/param.h>
+#include <sys/sysctl.h>
+#include <sys/stat.h>
+#include <cstdlib>
+#endif
+
 namespace NEO {
 
 namespace IoctlHelper {
@@ -104,6 +111,30 @@ int Drm::getEnabledPooledEu(int &enabled) {
 
 int Drm::getMaxGpuFrequency(int &maxGpuFrequency) {
     maxGpuFrequency = 0;
+#if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
+    struct stat sb;
+    if (fstat(getFileDescriptor(), &sb)) {
+        return 0;
+    }
+    char name[SPECNAMELEN + 1];
+    if (!devname_r(sb.st_rdev, S_IFCHR, name, sizeof(name))) {
+        return 0;
+    }
+    int id;
+    if (!sscanf(name, "drm/%d", &id) && !sscanf(name, "dri/renderD%d", &id)) {
+        return 0;
+    }
+
+    char oid[MAXPATHLEN + 1];
+    char max_freq[PAGE_SIZE];
+    size_t len = sizeof(max_freq);
+    snprintf(oid, sizeof(oid), "sys.class.drm.card%d.gt_max_freq_mhz", id - 128);
+    if (sysctlbyname(oid, &max_freq, &len, NULL, 0)) {
+        return 0;
+    }
+
+    maxGpuFrequency = std::stoi(max_freq);
+#else
     std::string clockSysFsPath = getSysFsPciPath();
 
     clockSysFsPath += "/gt_max_freq_mhz";
@@ -115,6 +146,7 @@ int Drm::getMaxGpuFrequency(int &maxGpuFrequency) {
 
     ifs >> maxGpuFrequency;
     ifs.close();
+#endif
     return 0;
 }