Tim Wawrzynczak has uploaded this change for review.

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fw_config: Default to undefined fw_config value

If for some reason a value for fw_config cannot be located, set its
value to a magic undefined value. The current `fw_config_probe` function
is modified to return true if fw_config is undefined, and a new function
`fw_config_probe_nodefault` is added which will return false if the
fw_config value is undefined. A new Kconfig option is added,
FW_CONFIG_IGNORE_UNDEFINED (defaults to n), which controls the behavior
of fw_config probing the devicetree.

Signed-off-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Change-Id: Ib3046233667e97a5f78961fabacbeb3099b3d442
---
M src/Kconfig
M src/include/fw_config.h
M src/lib/fw_config.c
3 files changed, 43 insertions(+), 5 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/56/47956/1

diff --git a/src/Kconfig b/src/Kconfig
index dc98ca2..a0f692c 100644
--- a/src/Kconfig
+++ b/src/Kconfig
@@ -398,6 +398,16 @@
 	  is not tried if FW_CONFIG_SOURCE_CBFS is enabled and the value was
 	  found in CBFS.
 
+config FW_CONFIG_IGNORE_UNDEFINED
+	bool "Undefined Firmware Configuration value will not probe devices"
+	depends on FW_CONFIG
+	default n
+	help
+	  When probing devices with fw_config, when the value is undefined or
+	  unable to be located, all devices will be successfully probed, and
+	  fw_config_probe will always return true. Set this to 'y' if you do
+	  not want this behavior.
+
 config HAVE_RAMPAYLOAD
 	bool
 
diff --git a/src/include/fw_config.h b/src/include/fw_config.h
index 3c87725..e02a38e 100644
--- a/src/include/fw_config.h
+++ b/src/include/fw_config.h
@@ -45,11 +45,21 @@
  * fw_config_probe() - Check if field and option matches.
  * @match: Structure containing field and option to probe.
  *
- * Return %true if match is found, %false if match is not found.
+ * Return %true if match is found or fw_config value is undefined.
+ *        %false if match is not found.
  */
 bool fw_config_probe(const struct fw_config *match);
 
 /**
+ * fw_config_probe_nodefault() - Check if field and option matches.
+ * @match: Structure containing field and option to probe.
+ *
+ * Return %true if match is found.
+ *        %false if match is not found or fw_config value is undefined
+ */
+bool fw_config_probe_nodefault(const struct fw_config *match);
+
+/**
  * fw_config_for_each_found() - Call a callback for each fw_config field found
  * @cb: The callback function
  * @arg: A context argument that is passed to the callback
diff --git a/src/lib/fw_config.c b/src/lib/fw_config.c
index e17d40e..efbee01 100644
--- a/src/lib/fw_config.c
+++ b/src/lib/fw_config.c
@@ -29,7 +29,7 @@
 					CBFS_TYPE_RAW) != sizeof(fw_config_value)) {
 			printk(BIOS_WARNING, "%s: Could not get fw_config from CBFS\n",
 			       __func__);
-			fw_config_value = 0;
+			fw_config_value = UNDEFINED_FW_CONFIG;
 		} else {
 			printk(BIOS_INFO, "FW_CONFIG value from CBFS is 0x%" PRIx64 "\n",
 			       fw_config_value);
@@ -39,16 +39,24 @@
 
 	/* Read the value from EC CBI. */
 	if (CONFIG(FW_CONFIG_SOURCE_CHROMEEC_CBI)) {
-		if (google_chromeec_cbi_get_fw_config(&fw_config_value))
+		if (google_chromeec_cbi_get_fw_config(&fw_config_value)) {
 			printk(BIOS_WARNING, "%s: Could not get fw_config from EC\n", __func__);
+			fw_config_value = UNDEFINED_FW_CONFIG;
+		}
 	}
 
 	printk(BIOS_INFO, "FW_CONFIG value is 0x%" PRIx64 "\n", fw_config_value);
 	return fw_config_value;
 }
 
-bool fw_config_probe(const struct fw_config *match)
+static bool fw_config_match(const struct fw_config *match, bool undefined_match)
 {
+	uint64_t fw_config;
+
+	fw_config = fw_config_get();
+	if (fw_config == UNDEFINED_FW_CONFIG)
+		return undefined_match;
+
 	/* Compare to system value. */
 	if ((fw_config_get() & match->mask) == match->value) {
 		if (match->field_name && match->option_name)
@@ -64,6 +72,16 @@
 	return false;
 }
 
+bool fw_config_probe(const struct fw_config *match)
+{
+	return fw_config_match(match, true);
+}
+
+bool fw_config_probe_nodefault(const struct fw_config *match)
+{
+	return fw_config_match(match, false);
+}
+
 #if ENV_RAMSTAGE
 
 /*
@@ -111,7 +129,7 @@
 			continue;
 
 		for (probe = dev->probe_list; probe && probe->mask != 0; probe++) {
-			if (fw_config_probe(probe)) {
+			if (fw_config_match(probe, (bool)!CONFIG(FW_CONFIG_IGNORE_UNDEFINED))) {
 				match = true;
 				cached_configs[probe_index(probe->mask)] = probe;
 				break;

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