Make socketcan backend compile on pre 3.6 kernels

The CanFD implementation was introduced by the Linux 3.6 kernel.
This change makes the socketcan backend compile on the older Linux
kernel build platforms.

If a socketcan backend was compiled against the most recent kernel
headers but run on an ancient kernel, the missing support is
dynamically detected by virtue of returned error code from
ioctl et al.

Task-number: QTBUG-51932
Change-Id: I5c3601877fa6e882f24d7fa3588dae473a325b9b
Reviewed-by: Rolf Eike Beer <eb@emlix.com>
Reviewed-by: Alex Blasche <alexander.blasche@theqtcompany.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/src/plugins/canbus/socketcan/socketcanbackend.cpp b/src/plugins/canbus/socketcan/socketcanbackend.cpp
index 122b546..48a2aaf 100644
--- a/src/plugins/canbus/socketcan/socketcanbackend.cpp
+++ b/src/plugins/canbus/socketcan/socketcanbackend.cpp
@@ -48,6 +48,30 @@
 #include <sys/ioctl.h>
 #include <sys/time.h>
 
+#ifndef CANFD_MTU
+// CANFD support was added by Linux kernel 3.6
+// For prior kernels we redefine the missing defines here
+// they are taken from linux/can/raw.h & linux/can.h
+
+enum {
+    CAN_RAW_FD_FRAMES = 5
+};
+
+#define CAN_MAX_DLEN 8
+#define CANFD_MAX_DLEN 64
+struct canfd_frame {
+    canid_t can_id;  /* 32 bit CAN_ID + EFF/RTR/ERR flags */
+    __u8    len;     /* frame payload length in byte */
+    __u8    flags;   /* additional flags for CAN FD */
+    __u8    __res0;  /* reserved / padding */
+    __u8    __res1;  /* reserved / padding */
+    __u8    data[CANFD_MAX_DLEN] __attribute__((aligned(8)));
+};
+#define CAN_MTU     (sizeof(struct can_frame))
+#define CANFD_MTU   (sizeof(struct canfd_frame))
+
+#endif
+
 QT_BEGIN_NAMESPACE
 
 SocketCanBackend::SocketCanBackend(const QString &name) :