fw_config: Add firmware configuration interface

This change introduces a new top-level interface for interacting with a
bitmask providing firmware configuration information.

This is motivated by Chromebook mainboards that need to support multiple
different configurations at runtime with the same BIOS.  In these
devices the Embedded Controller provides a bitmask that can be broken
down into different fields and each field can then be broken down into
different options.

The firmware configuration value could also be stored in CBFS and this
interface will look in CBFS first to allow the Embedded Controller value
to be overridden.

The firmware configuration interface is intended to easily integrate
into devicetree.cb and lead to less code duplication for new mainboards
that make use of this feature.

BUG=b:147462631
TEST=this provides a new interface that is tested in subsequent commits

Change-Id: I1e889c235a81545e2ec0e3a34dfa750ac828a330
Signed-off-by: Duncan Laurie <dlaurie@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/41209
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

2 files changed, 57 insertions, 0 deletions

diff --git a/src/include/device/device.h b/src/include/device/device.h
index 46efbfe679..082dcbb4d3 100644
--- a/src/include/device/device.h
+++ b/src/include/device/device.h
@@ -8,6 +8,7 @@
 #include <smbios.h>
 #include <types.h>
 
+struct fw_config;
 struct device;
 struct pci_operations;
 struct i2c_bus_operations;
@@ -147,6 +148,9 @@ struct device {
 #endif
 #endif
 	DEVTREE_CONST void *chip_info;
+
+	/* Zero-terminated array of fields and options to probe. */
+	DEVTREE_CONST struct fw_config *probe_list;
 };
 
 /**
diff --git a/src/include/fw_config.h b/src/include/fw_config.h
new file mode 100644
index 0000000000..d41afd6c5d
--- /dev/null
+++ b/src/include/fw_config.h
@@ -0,0 +1,53 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef __FW_CONFIG__
+#define __FW_CONFIG__
+
+#include <device/device.h>
+#include <static.h>  /* Provides fw_config definitions from devicetree.cb */
+#include <stdbool.h>
+#include <stdint.h>
+
+/**
+ * struct fw_config - Firmware configuration field and option.
+ * @field_name: Name of the field that this option belongs to.
+ * @option_name: Name of the option within this field.
+ * @mask: Bitmask of the field.
+ * @value: Value of the option within the mask.
+ */
+struct fw_config {
+	const char *field_name;
+	const char *option_name;
+	uint32_t mask;
+	uint32_t value;
+};
+
+/* Generate a pointer to a compound literal of the fw_config structure. */
+#define FW_CONFIG(__field, __option)	(&(const struct fw_config) {		\
+	.field_name = FW_CONFIG_FIELD_##__field##_NAME,				\
+	.option_name = FW_CONFIG_FIELD_##__field##_OPTION_##__option##_NAME,	\
+	.mask = FW_CONFIG_FIELD_##__field##_MASK,				\
+	.value = FW_CONFIG_FIELD_##__field##_OPTION_##__option##_VALUE		\
+})
+
+#if CONFIG(FW_CONFIG)
+
+/**
+ * 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.
+ */
+bool fw_config_probe(const struct fw_config *match);
+
+#else
+
+static inline bool fw_config_probe(const struct fw_config *match)
+{
+	/* Always return true when probing with disabled fw_config. */
+	return true;
+}
+
+#endif /* CONFIG(FW_CONFIG) */
+
+#endif /* __FW_CONFIG__ */