linux/cxl: merge CXLDevice attributes when interleaved

And add CXLDeviceInterleaveWays

Signed-off-by: Brice Goglin <Brice.Goglin@inria.fr>

doc/hwloc.doxy

@@ -2244,8 +2244,12 @@ These info attributes are attached to objects specified in parentheses.
 <dl>
 <dt>CXLDevice (NUMA Nodes or DAX Memory OS devices)</dt>
 <dd>The PCI/CXL bus ID of a device whose CXL Type-3 memory is exposed here.
-There may be multiple instances of this attributes if multiple device memories
-are interleaved.
+If multiple devices are interleaved, their bus IDs are separated by commas,
+and the number of devices in reported in CXLDeviceInterleaveWays.
+</dd>
+<dt>CXLDeviceInterleaveWays (NUMA Nodes or DAX Memory OS devices)</dt>
+<dd>If multiple CXL devices are interleaved, this attribute shows the
+number of devices (and the number of bus IDs in the CXLDevice attributes).
 </dd>
 <dt>DAXDevice (NUMA Nodes)</dt>
 <dd>The name of the Linux DAX device that was used to expose a non-volatile

hwloc/topology-linux.c

@@ -3708,7 +3708,11 @@ static int
 annotate_cxl_dax(hwloc_obj_t obj, unsigned region, int root_fd)
 {
   char path[300];
+  char bdfs[(12+1)*16]; /* 16 interleaved devices max, 12 chars par BDF, comma-separated + ending \0 */
+  char *curbdfptr = bdfs;
+  unsigned interleave_ways = 0;
   unsigned i;
+  *curbdfptr = '\0';
 
   for(i=0; ; i++) {
     char decoder[20]; /* "decoderX.Y" */
@@ -3760,8 +3764,27 @@ annotate_cxl_dax(hwloc_obj_t obj, unsigned region, int root_fd)
     }
     *slash = '\0';
     if (pcibdf) {
-      hwloc_obj_add_info(obj, "CXLDevice", pcibdf);
+      if (interleave_ways) {
+        if (interleave_ways >= 16) {
+          if (HWLOC_SHOW_CRITICAL_ERRORS())
+            fprintf(stderr, "Found more than 16 interleaved devices for region%u, ignoring the last ones.\n", region);
+          break;
+        }
+        *(curbdfptr++) = ',';
+      }
+      strcpy(curbdfptr, pcibdf);
+      curbdfptr += 12;
+      interleave_ways++;
+    }
+  }
+
+  if (interleave_ways) {
+    if (interleave_ways > 1) {
+      char tmp[12]; /* interleave ways is 16 max */
+      snprintf(tmp, sizeof(tmp), "%u", interleave_ways);
+      hwloc_obj_add_info(obj, "CXLDeviceInterleaveWays", tmp);
     }
+    hwloc_obj_add_info(obj, "CXLDevice", bdfs);
   }
 
   return 0;