zephyr-flash-pyocd.bbclass: Implement configurable probe IDs to program

Implement logic to configure what probes to program based on the
PYOCD_FLASH_IDS variable:
1. by default program all attached probes
2. change default behaviour by listing the probe IDs to flash

CONNECT_TIMEOUT_SECONDS was also renamed to maintain consistency with
the PYOCD_FLASH_IDS variable.

One can query the IDs using `pyocd list`.

The value of PYOCD_FLASH_IDS can also be injected into the datastore
using BB_ENV_EXTRAWHITE.

Signed-off-by: Andrei Gherzan <andrei.gherzan@huawei.com>
Signed-off-by: Naveen Saini <naveen.kumar.saini@intel.com>

README.txt

@@ -67,6 +67,15 @@ dfu-util and/or pyocd need to be installed in your system. If you observe
 permission errors or the flashing process seem to hang, follow those instructions:
 https://github.com/pyocd/pyOCD/tree/master/udev
 
+By default, pyocd tries to flash all the attached probes. This behaviour can be
+customised by defining the PYOCD_FLASH_IDS variable as a space-separated list
+of IDs. Once that is set, the tool will only try to program these IDs. You can
+query for the IDs by running `pyocd list` on your host while having the probes
+attached. Besides setting this variable through the build's configuration or
+metadata, you can also inject its value from command line with something like:
+
+    $ PYOCD_FLASH_IDS='<ID1> <ID2> <ID3>' BB_ENV_EXTRAWHITE="$BB_ENV_EXTRAWHITE PYOCD_FLASH_IDS" bitbake <TARGET> -c flash_usb
+
 Building and Running Zephyr Tests
 =================================
 Presently only toolchains for ARM, x86, IAMCU and Nios2 are supported.

classes/zephyr-flash-pyocd.bbclass

@@ -1,4 +1,5 @@
-CONNECT_TIMEOUT_SECONDS ?= "30"
+PYOCD_CONNECT_TIMEOUT_SECONDS ?= "30"
+PYOCD_FLASH_IDS ?= "all"
 
 python do_flash_usb() {
     try:
@@ -7,26 +8,46 @@ python do_flash_usb() {
     except ImportError:
         bb.fatal("Flashing with pyocd needs the relevant python package. Make sure your host provides it or consult your distribution packages for how to install this prerequisite.")
 
-    timeout = int(d.getVar('CONNECT_TIMEOUT_SECONDS'))
+    try:
+        timeout = int(d.getVar('PYOCD_CONNECT_TIMEOUT_SECONDS'))
+    except ValueError:
+        bb.fatal(f"PYOCD_CONNECT_TIMEOUT_SECONDS was set to an invalid value: {d.getVar('PYOCD_CONNECT_TIMEOUT_SECONDS')}.")
     image = f"{d.getVar('DEPLOY_DIR_IMAGE')}/{d.getVar('PN')}.elf"
-    bb.plain(f"Attempting to flash {image} to board {d.getVar('BOARD')}")
+    ids = d.getVar('PYOCD_FLASH_IDS')
 
-    # Try to connect to a probe with a timeout
-    now = 0
-    step = 3
-    while True:
-        session = ConnectHelper.session_with_chosen_probe(blocking=False, return_first=True)
-        if session:
-            break
-        if now >= timeout:
-            bb.fatal("Timeout while trying to connect to a probe. Make sure the target device is connected and the udev is configured accordingly. See <https://github.com/mbedmicro/pyOCD/tree/master/udev> for help.")
-        bb.warn("Can't connect to the probe. Retrying in %d seconds..." % step)
-        time.sleep(step)
-        now += step
+    # Compute the list of IDs to program
+    if ids == 'all':
+        ids = []
+        for probe in ConnectHelper.get_all_connected_probes(blocking=False):
+            ids.append(probe.unique_id)
+        if not ids:
+            bb.fatal("No probe detected. Make sure your target is connected.")
+    else:
+        ids = ids.split()
+        if not ids:
+            bb.fatal("No probe requested for programming. Make sure PYOCD_FLASH_IDS is set.")
 
-    with session:
-        FileProgrammer(session).program(image)
-        session.board.target.reset()
+    # Program each ID
+    for id in ids:
+        bb.plain(f"Attempting to flash {os.path.basename(image)} to board {d.getVar('BOARD')} [{id}]")
+
+        # Try to connect to a probe with a timeout
+        now = 0
+        step = 3
+        while True:
+            session = ConnectHelper.session_with_chosen_probe(blocking=False, return_first=True, unique_id=id)
+            if session:
+                break
+            if now >= timeout:
+                bb.fatal(f"Timeout while trying to connect to probe ID: {id}. Make sure the target device is connected and the udev is configured accordingly. See <https://github.com/mbedmicro/pyOCD/tree/master/udev> for help.")
+            bb.warn(f"Can't connect to the probe ID: {id}. Retrying in {step} seconds...")
+            time.sleep(step)
+            now += step
+
+        # Program the selected probe
+        with session:
+            FileProgrammer(session).program(image)
+            session.board.target.reset()
 }
 
 addtask do_flash_usb after do_deploy