Re: [Xenomai-core] Re: Extended CAN frame filtering

Sat, 17 Feb 2007 10:20:42 -0800 

Jan Kiszka wrote:

Wolfgang Grandegger wrote:
...

Attached is a patch adding the CAN_INV_FILTER feature. It also updates
the doc. Now the filter scheme should be compatible with Socket-CAN. If
it's OK, I will check it in (or you can do it).

Wolfgang.


------------------------------------------------------------------------

Index: include/rtdm/rtcan.h
===================================================================
--- include/rtdm/rtcan.h        (revision 2193)
+++ include/rtdm/rtcan.h        (working copy)


Please increment the profile revision (2 spots: #define and
documentation text).


@@ -441,28 +441,38 @@ typedef enum CAN_STATE can_state_t;
#define CAN_STATE_OPERATING(state) ((state) < CAN_STATE_BUS_OFF) +/** Invert CAN filter definition */ 
+#define CAN_INV_FILTER      CAN_ERR_FLAG
+


I would move this close to the other CAN ID flags and explain explicitly
which one is valid in which context. Both are sharing the same bit, so
confusion can arise.
I already thought about it but was unsure if it's less confusing. OK, one more pro, I will change it. 




 /**
  * Filter for reception of CAN messages.
  *
  * This filter works as follows:
  * A received CAN ID is AND'ed bitwise with @c can_mask and then compared to
- * @c can_id. If this comparison is true the message will be received by the
- * socket.
+ * @c can_id. This also includes the @ref CAN_EFF_FLAG and @ref CAN_RTR_FLAG
+ * of @ref CAN_xxx_FLAG. If this comparison is true, the message will be
+ * received by the socket. The logic can be inverted with the @c can_id flag
+ * @ref CAN_INV_FILTER :
+ *
+ * @code
+ * if (can_id & CAN_INV_FILTER) {
+ *    if ((received_can_id & can_mask) != (can_id & ~CAN_INV_FILTER))
+ *       accept-message;
+ * } else {
+ *    if ((received_can_id & can_mask) == can_id)
+ *       accept-message;
+ * }
+ * @endcode


Nice and helpful!


  *
- * Multiple filters can be arranged in a filter list and set with - * @ref Sockopts. If one of these filters matches a CAN ID upon reception + * Multiple filters can be arranged in a filter list and set with 
+ * @ref Sockopts. If one of these filters matches a CAN ID upon reception
  * of a CAN frame, this frame is accepted.
  *
- * @note Only @ref CAN_EFF_FLAG of @ref CAN_xxx_FLAG "CAN ID flags" is
- * valid for @c can_id and none for @c can_mask. This means that the RTR bit
- * is not taken into account while filtering messages.
- *
- * Extended IDs are received only if @ref CAN_EFF_FLAG is set in
- * @c can_id. If it is cleared only standard IDs are accepted.
  */
 typedef struct can_filter {
- /** CAN ID which must match with incoming IDs after passing the mask */ 
+    /** CAN ID which must match with incoming IDs after passing the mask.
+     *  The filter logic can be inverted with the flag @ref CAN_INV_FILTER. */
     uint32_t    can_id;
/** Mask which is applied to incoming IDs. See @ref CAN_xxx_MASK 
@@ -470,12 +480,11 @@ typedef struct can_filter {
     uint32_t    can_mask;
 } can_filter_t;
- 
 /**
  * Socket address structure for the CAN address family
  */
 struct sockaddr_can {
- /** CAN address family, must be @c AF_CAN */ + /** CAN address family, must be @c AF_CAN */ 
     sa_family_t  can_family;
     /** Interface index of CAN controller. See @ref SIOCGIFINDEX. */
     int          can_ifindex;
Index: ksrc/drivers/can/rtcan_module.c
===================================================================
--- ksrc/drivers/can/rtcan_module.c     (revision 2193)
+++ ksrc/drivers/can/rtcan_module.c     (working copy)
@@ -262,11 +262,11 @@ static int rtcan_read_proc_filter(char *
     rtdm_lockctx_t lock_ctx;
     RTCAN_PROC_PRINT_VARS(80);
- /* fd __CAN_ID__ _CAN_Mask_ MatchCount 
-     *   3 0x12345678 0x12345678 1234567890
+    /*  fd __CAN_ID__ _CAN_Mask_ Inv MatchCount
+     *   3 0x12345678 0x12345678  no 1234567890
      */
- - if (!RTCAN_PROC_PRINT("fd __CAN_ID__ _CAN_Mask_ MatchCount\n")) 
+
+    if (!RTCAN_PROC_PRINT("fd __CAN_ID__ _CAN_Mask_ Inv MatchCount\n"))
         goto done;
rtdm_lock_get_irqsave(&rtcan_recv_list_lock, lock_ctx); 
@@ -275,10 +275,13 @@ static int rtcan_read_proc_filter(char *
     while (recv_listener != NULL) {
        context = rtcan_socket_context(recv_listener->sock);
- if (!RTCAN_PROC_PRINT("%2d 0x%08x 0x%08x %10d\n", - context->fd, + if (!RTCAN_PROC_PRINT("%2d 0x%08x 0x%08x %s %10d\n", 
+                             context->fd,
                              recv_listener->can_filter.can_id,
-                             recv_listener->can_filter.can_mask,
+                             recv_listener->can_filter.can_mask &
+                             ~CAN_INV_FILTER,
+                             (recv_listener->can_filter.can_mask &
+                              CAN_INV_FILTER) ? "yes" : " no",
                              recv_listener->match_count))
            break;
        recv_listener = recv_listener->next;
Index: ksrc/drivers/can/rtcan_raw.c
===================================================================
--- ksrc/drivers/can/rtcan_raw.c        (revision 2193)
+++ ksrc/drivers/can/rtcan_raw.c        (working copy)
@@ -67,7 +67,10 @@ static struct rtdm_device rtcan_proto_ra
static inline int rtcan_accept_msg(uint32_t can_id, can_filter_t *filter) 
 {
-    return ((can_id & filter->can_mask) == filter->can_id);
+    if ((filter->can_mask & CAN_INV_FILTER))
+       return ((can_id & filter->can_mask) != filter->can_id);
+    else
+       return ((can_id & filter->can_mask) == filter->can_id);
 }
Index: ksrc/drivers/can/rtcan_raw_filter.c 
===================================================================
--- ksrc/drivers/can/rtcan_raw_filter.c (revision 2193)
+++ ksrc/drivers/can/rtcan_raw_filter.c (working copy)
@@ -55,13 +55,13 @@ void rtcan_raw_print_filter(struct rtcan
 static inline void rtcan_raw_mount_filter(can_filter_t *recv_filter,
                                          can_filter_t *filter)
 {
-   if (filter->can_id & CAN_EFF_FLAG)
-       recv_filter->can_mask = ((filter->can_mask & CAN_EFF_MASK) |
-                                CAN_EFF_FLAG);
-    else
-       recv_filter->can_mask = (filter->can_mask & CAN_SFF_MASK);
-
-    recv_filter->can_id = filter->can_id & recv_filter->can_mask;
+    if (filter->can_id & CAN_INV_FILTER) {
+       recv_filter->can_id = filter->can_id & ~CAN_INV_FILTER;
+       recv_filter->can_mask = filter->can_mask | CAN_INV_FILTER;
+    } else {
+       recv_filter->can_id = filter->can_id;
+       recv_filter->can_mask = filter->can_mask & ~CAN_INV_FILTER;
+    }


Why do you push CAN_INV_FILTER internally into the mask instead of
keeping it in the filter's ID - as the pseudo code above states?
To simplify the filter calculation. It actually avoids the expression (filter->can_id & ~CAN_INV_FILTER). As this is in a very frequently called function, I think it's worth the trick. 

Wolfgang.


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