[make-initrd] [PATCH v6 15/22] bootchain-core: introduces the built-in "noop" pseudo-step

[Leonid Krivoshein]

Usually the <OUT> of a step automatically matches the <IN> of the next step.
The "noop" step does nothing and is intended to separate the <OUT> of the
previous step from the <IN> of the next step.

Signed-off-by: Leonid Krivoshein <klark.devel at gmail.com>
---
 features/bootchain-core/README.md        | 17 +++++++++++++++++
 features/bootchain-core/data/sbin/chaind |  8 +++++++-
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/features/bootchain-core/README.md b/features/bootchain-core/README.md
index ffed599..db73c0a 100644
--- a/features/bootchain-core/README.md
+++ b/features/bootchain-core/README.md
@@ -49,6 +49,11 @@ us to optimize fill in `initramfs` only which we are need.
 
 - Modularity: loading methods are initially separated from the common
   code and daemon.
+- Some steps (actions) are built directly into the code of the main loop
+  of the `chaind` daemon, external scripts are not called to execute them.
+  Such pseudo-steps allow you to control, basically, the internal state of the
+  daemon and should not be taken into account in the boot chain, as if they are
+  hidden.
 - `bootchain-sh-functions` extends the API of the original `pipeline-sh-functions`,
   see the details in the corresponding section.
 - Via resolve_target() supports not only forward, but also reverse addressing,
@@ -93,6 +98,18 @@ parameters:
 Other `bootchain-*` modules can also use this configuration file for their
 own needs.
 
+## In-app pseudo-steps
+
+All the steps listed below are an extension of the `pipeline`. They are
+embedded in the code of the main loop of the `boot chain-loop` daemon, do
+not need additional parameters and should not be taken into account when
+addressing, as if they are hidden.
+
+- `noop` - does not perform any actions and is designed to pull off the results
+  on the <OUT> of the previous step from the <IN> of the next step, which can
+  be useful, for example, when we don`t want the results of the `waitdev` step
+  to be used in the next step, `localdev`, which primarily looks at them.
+
 ## External elements of the bootchain (steps-scripts)
 
 - `mountfs` - mounts a file or device from the result of the previous or other
diff --git a/features/bootchain-core/data/sbin/chaind b/features/bootchain-core/data/sbin/chaind
index 9224c40..5623a37 100755
--- a/features/bootchain-core/data/sbin/chaind
+++ b/features/bootchain-core/data/sbin/chaind
@@ -48,7 +48,13 @@ while [ -n "$chainsteps" ]; do
 	name="${chainsteps%%,*}"
 	exe="$handlerdir/$name"
 
-	if [ -x "$exe" ]; then
+	if [ "$name" = noop ]; then
+		chainsteps="${chainsteps#$name}"
+		chainsteps="${chainsteps#,}"
+		prevdir=
+		message "[0] Step '$name' has been passed"
+
+	elif [ -x "$exe" ]; then
 		assign "callnum" "\${callnum_$name:-0}"
 		datadir="$mntdir/src/step$stepnum"
 		destdir="$mntdir/dst/step$stepnum"
-- 
2.24.1