vendorcode/google/chromeos: Add API for Chromebook Plus check

This patch implements an API which relies on the
chromeos_get_factory_config() function to retrieve the factory
config value.

This information is useful to determine whether a ChromeOS device
is branded as a Chromebook Plus based on specific bit flags:

   - Bit 4 (0x10): Indicates whether the device chassis has the
                  "chromebook-plus" branding.
   - Bits 3-0 (0x1): Must be 0x1 to signify compliance with
		   Chromebook Plus hardware specifications.

BUG=b:317880956
TEST=Able to verify that google/screebo is branded as
Chromebook Plus.

Change-Id: Iebaed1c60e34af4cc36316f1f87a89df778b0857
Signed-off-by: Subrata Banik <subratabanik@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/79763
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kapil Porwal <kapilporwal@google.com>

src/vendorcode/google/chromeos/chromeos.h

@@ -32,6 +32,18 @@ void chromeos_set_ramoops(void *ram_oops, size_t size);
  * Return `-1` in case of error.
  */
 int64_t chromeos_get_factory_config(void);
+/*
+ * Determines whether a ChromeOS device is branded as a Chromebook Plus
+ * based on specific bit flags:
+ *
+ * - Bit 4 (0x10): Indicates whether the device chassis has the
+ *                 "chromebook-plus" branding.
+ * - Bits 3-0 (0x1): Must be 0x1 to signify compliance with Chromebook Plus
+ *                   hardware specifications.
+ *
+ * To be considered a Chromebook Plus, either of these conditions needs to be met.
+ */
+bool chromeos_device_branded_plus(void);
 
 /*
  * Declaration for mainboards to use to generate ACPI-specific ChromeOS needs.

src/vendorcode/google/chromeos/tpm_factory_config.c

@@ -2,8 +2,13 @@
 
 #include <console/console.h>
 #include <security/tpm/tss.h>
+#include <types.h>
 #include <vendorcode/google/chromeos/chromeos.h>
 
+#define CHROMEBOOK_PLUS_HARD_BRANDED BIT(4)
+#define CHROMEBOOK_PLUS_SOFT_BRANDED BIT(0)
+#define CHROMEBOOK_PLUS_DEVICE (CHROMEBOOK_PLUS_HARD_BRANDED | CHROMEBOOK_PLUS_SOFT_BRANDED)
+
 int64_t chromeos_get_factory_config(void)
 {
 	static int64_t factory_config = -1;
@@ -29,3 +34,24 @@ int64_t chromeos_get_factory_config(void)
 
 	return factory_config;
 }
+
+/*
+ * Determines whether a ChromeOS device is branded as a Chromebook Plus
+ * based on specific bit flags:
+ *
+ * - Bit 4 (0x10): Indicates whether the device chassis has the
+ *                 "chromebook-plus" branding.
+ * - Bits 3-0 (0x1): Must be 0x1 to signify compliance with Chromebook Plus
+ *                   hardware specifications.
+ *
+ * To be considered a Chromebook Plus, either of these conditions needs to be met.
+ */
+bool chromeos_device_branded_plus(void)
+{
+	int64_t factory_config = chromeos_get_factory_config();
+
+	if (factory_config < 0)
+		return false;
+
+	return factory_config & CHROMEBOOK_PLUS_DEVICE;
+}