From 51a6923008deb97b926b203c32e52e6cd2beda3a Mon Sep 17 00:00:00 2001
From: rdb <git@rdb.name>
Date: Mon, 5 Apr 2021 17:19:47 +0200
Subject: [PATCH] device: Work around FreeBSD kernel bug for querying gamepad
 axes

This is to support older kernels, which always returned 0 from successful ioctl, rather than the number of bits.  This was fixed in the FreeBSD kernel trunk.
---
 panda/src/device/evdevInputDevice.cxx | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/panda/src/device/evdevInputDevice.cxx b/panda/src/device/evdevInputDevice.cxx
index b609501797..9cf94e1dfc 100644
--- a/panda/src/device/evdevInputDevice.cxx
+++ b/panda/src/device/evdevInputDevice.cxx
@@ -328,7 +328,22 @@ init_device() {
   uint8_t axes[(ABS_MAX + 8) >> 3] = {0};
   if (test_bit(EV_ABS, evtypes)) {
     // Check which axes are on the device.
-    num_bits = ioctl(_fd, EVIOCGBIT(EV_ABS, sizeof(axes)), axes) << 3;
+    int result = ioctl(_fd, EVIOCGBIT(EV_ABS, sizeof(axes)), axes);
+#ifdef __FreeBSD__
+    // Older kernels had a bug where this would always return 0, see D28218
+    if (result == 0) {
+      for (int i = ABS_MAX; i >= 0; --i) {
+        if (test_bit(i, axes)) {
+          num_bits = i + 1;
+          break;
+        }
+      }
+    }
+    else
+#endif
+    if (result > 0) {
+      num_bits = result << 3;
+    }
     has_axes = true;
   }