Change in coreboot[master]: option: Add API for mainboard provided options

[Patrick Rudolph (Code Review)]

Patrick Rudolph has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/52601 )

Change subject: option: Add API for mainboard provided options
......................................................................

option: Add API for mainboard provided options

This API can be implemented by mainboards providing a custom option storage.
For example an external I2C EEPROM, IPMI on BMC, ...

Update documentation accordingly.

Change-Id: Ic5bbb5b3353d862c5533f90ced4824eec27ca3b9
Signed-off-by: Patrick Rudolph 
---
M Documentation/index.md
A Documentation/lib/option.md
M src/Kconfig
M src/include/option.h
4 files changed, 48 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/01/52601/1

diff --git a/Documentation/index.md b/Documentation/index.md
index 9870cf3..b4a42cd 100644
--- a/Documentation/index.md
+++ b/Documentation/index.md
@@ -182,6 +182,7 @@
 * [System on Chip](soc/index.md)
 * [Mainboard](mainboard/index.md)
 * [Payloads](lib/payloads/index.md)
+* [Options](lib/option.md)
 * [Libraries](lib/index.md)
 * [Security](security/index.md)
 * [SuperIO](superio/index.md)
diff --git a/Documentation/lib/option.md b/Documentation/lib/option.md
new file mode 100644
index 0000000..c65728f
--- /dev/null
+++ b/Documentation/lib/option.md
@@ -0,0 +1,30 @@
+# Option framework
+
+The option framework around `set_option(const char *name, void *val)` and
+`get_option(void *dest, const char *name)` was deprecated in favour of a
+typesafe API.
+
+Historically the option framework used the persistent NVRAM backed by the
+RTC battery on PC platforms. On todays platforms options are usually
+stored in the firmware flash as well.
+
+The new typesafe option framework can be used by calling
+`enum cb_err set_int_option(const char *name, int value)` and
+`int get_int_option(const char *name, const int fallback)`.
+
+# Mainboard option framework
+
+Mainboards that do not use NVRAM, but a vendor specific method, to store
+firmware settings must select `USE_MAINBOARD_OPTION_TABLE`.
+
+In addition it must implement the following methods:
+
+```
+enum cb_err mainboard_set_option(const char *name, const void *val, const size_t size);
+enum cb_err mainboard_get_option(const char *name, void *dest, size_t *size_in_out);
+```
+
+Possible vendor specific stores are:
+* BMC (configurable over IPMI or WebUI)
+* I2C EEPROM
+* ...
diff --git a/src/Kconfig b/src/Kconfig
index fe325e8..8566a56 100644
--- a/src/Kconfig
+++ b/src/Kconfig
@@ -127,6 +127,12 @@
      Enable this option if coreboot shall read options from the "CMOS"
      NVRAM instead of using hard-coded values.

+config USE_MAINBOARD_OPTION_TABLE
+	bool
+	help
+	  Selected by mainboards that provide a custom interface to read and
+	  write options, for example an EEPROM or BMC interface.
+
 config STATIC_OPTION_TABLE
    bool "Load default configuration values into CMOS on each boot"
    depends on USE_OPTION_TABLE
diff --git a/src/include/option.h b/src/include/option.h
index 4de032b..4bfd33a 100644
--- a/src/include/option.h
+++ b/src/include/option.h
@@ -10,10 +10,15 @@
 enum cb_err cmos_set_option(const char *name, void *val);
 enum cb_err cmos_get_option(void *dest, const char *name);

+enum cb_err mainboard_set_option(const char *name, const void *val, const size_t size);
+enum cb_err mainboard_get_option(const char *name, void *dest, size_t *size_in_out);
+
 static inline enum cb_err set_int_option(const char *name, int value)
 {
    if (CONFIG(USE_OPTION_TABLE))
    	return cmos_set_option(name, &value);
+	else if (CONFIG(USE_MAINBOARD_OPTION_TABLE))
+		return mainboard_set_option(name, &value, sizeof(value));

return CB_CMOS_OTABLE_DISABLED;
 }
@@ -24,7 +29,13 @@
    	int value = 0;
    	if (cmos_get_option(&value, name) == CB_SUCCESS)
    		return value;
+	} else if (CONFIG(USE_MAINBOARD_OPTION_TABLE)) {
+		int value = 0;
+		size_t size = sizeof(value);
+		if (mainboard_get_option(name, &value, &size) == CB_SUCCESS)
+			return value;
    }
+
    return fallback;
 }