--- wikisrc/users/jakllsch.mdwn	2009/10/29 16:34:05	1.3
+++ wikisrc/users/jakllsch.mdwn	2010/05/01 20:15:13	1.4
@@ -1,5 +1,28 @@
 # Jonathan Kollasch
 
+## [[!template id=man name="ddb" section="4"]] tips
+
+### locating a softc
+This locates a device's softc using it's `cfdriver_t` (e.g. `&mainbus_cd`, `&cpu_cd`) and its "device unit" (e.g. the `0` in `mainbus0`).
+
+    db{0}> call device_lookup_private(ohci_cd, 0)
+    0xffff800045fb2008
+
+### locating structure members
+This uses [[!template id=man name="gdb" section="1"]] and a kernel with debugging symbols to find the offset to a element in a structure.
+
+    $ gdb netbsd.gdb
+    ...
+    (gdb) print &((struct ohci_softc *)0)->iot
+    $3 = (bus_space_tag_t *) 0x478
+    (gdb) print &((struct ohci_softc *)0)->ioh
+    $4 = (bus_space_handle_t *) 0x480
+
+### peeking at mapped registers
+
+    db{0}> call bus_space_read_4(*(ffff800045fb2008+478), *(ffff800045fb2008+480), 0)
+    0x110
+
 ## Unfinished Projects
 
 ### x86 UEFI kernel loader