Build workaround for kernels older than 2.6.39 (#260)

linux/hid.c

@@ -45,6 +45,22 @@
 
 #include "hidapi.h"
 
+#ifdef HIDAPI_ALLOW_BUILD_WORKAROUND_KERNEL_2_6_39
+/* This definitions first appeared in Linux Kernel 2.6.39 in linux/hidraw.h.
+    hidapi doesn't support kernels older than that,
+    so we don't define macros below explicitly, to fail builds on old kernels.
+    For those who really need this as a workaround (e.g. to be able to build on old build machines),
+    can workaround by defining the macro above.
+*/
+#ifndef HIDIOCSFEATURE
+#define HIDIOCSFEATURE(len)    _IOC(_IOC_WRITE|_IOC_READ, 'H', 0x06, len)
+#endif
+#ifndef HIDIOCGFEATURE
+#define HIDIOCGFEATURE(len)    _IOC(_IOC_WRITE|_IOC_READ, 'H', 0x07, len)
+#endif
+
+#endif
+
 
 /* USB HID device property names */
 const char *device_string_names[] = {