Auto-select JTAG transport when appropriate

I looked through all the target configs after stripping comments and
such from them with sed to see what jtag-specific commands can appear
first, and it looks like all the meaningful combinations should be
covered.

Change-Id: I8d543407b7f4ac8aca7354ecd50e841c8a04d5f3
Signed-off-by: Paul Fertser <fercerpav@gmail.com>
Reviewed-on: http://openocd.zylin.com/2179
Tested-by: jenkins
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>

src/jtag/startup.tcl

@@ -87,6 +87,32 @@ proc measure_clk {} {
 
 add_help_text measure_clk "Runs a test to measure the JTAG clk. Useful with RCLK / RTCK."
 
+proc default_to_jtag { f args } {
+	if [catch {transport select} current_transport] {
+		echo "Info : session transport was not selected, defaulting to JTAG"
+		transport select jtag
+		eval $f $args
+	} {
+		error "session transport is \"$current_transport\" but your config requires JTAG"
+	}
+}
+
+proc jtag args {
+	eval default_to_jtag jtag $args
+}
+
+proc jtag_rclk args {
+	eval default_to_jtag jtag_rclk $args
+}
+
+proc jtag_ntrst_delay args {
+	eval default_to_jtag jtag_ntrst_delay $args
+}
+
+proc jtag_ntrst_assert_width args {
+	eval default_to_jtag jtag_ntrst_assert_width $args
+}
+
 # BEGIN MIGRATION AIDS ...  these adapter operations originally had
 # JTAG-specific names despite the fact that the operations were not
 # specific to JTAG, or otherewise had troublesome/misleading names.

tcl/target/swj-dp.tcl

@@ -18,6 +18,11 @@
 # split out "chip" and "tag" so we can someday handle
 # them more uniformly irlen too...)
 
+if [catch {transport select}] {
+ echo "Info : session transport was not selected, defaulting to JTAG"
+ transport select jtag
+}
+
 proc swj_newdap {chip tag args} {
  if {[using_jtag]} { eval jtag newtap $chip $tag $args }
  if {[using_swd]} { eval swd newdap $chip $tag $args }