Add documentation to README.md describing the EFI protocols used by GBLHEADmastermain

Include the required, conditionally required, and optional protocols
in addition to a brief description of what the protocol does and how
it is used within GBL.

Bug: b/340322551

Change-Id: Id4909170643fe704e540455d6c7e8858175882f3

5 files changed, 88 insertions, 6 deletions

diff --git a/gbl/BUILD b/gbl/BUILD
index 6640908..96485a3 100644
--- a/gbl/BUILD
+++ b/gbl/BUILD
@@ -16,7 +16,7 @@ load(":readme.bzl", "readme_test")
 
 readme_test(
     name = "readme_test",
-    readme = "README.md",
+    readme = "docs/efi_protocols.md",
     # Note: can't read files in subpackages, not sure how to add a dependency on all,
     # globbed, subpackages and all the rust_lib targets they contain.
     deps = [
diff --git a/gbl/README.md b/gbl/README.md
index 430040a..d0b33c4 100644
--- a/gbl/README.md
+++ b/gbl/README.md
@@ -96,3 +96,7 @@ configurations:
        -drive format=raw,file=fat:rw:/tmp/esp,id=blk0 \
        -device virtio-blk-device,drive=blk0
    ```
+
+## EFI Protocols
+
+List of EFI protocols used by GBL and a brief description of each [here](./docs/efi_protocols.md).
diff --git a/gbl/docs/efi_protocols.md b/gbl/docs/efi_protocols.md
new file mode 100644
index 0000000..32d09f3
--- /dev/null
+++ b/gbl/docs/efi_protocols.md
@@ -0,0 +1,65 @@
+The EFI application of GBL requires certain EFI protocols in order to boot,
+and can require other protocols for certain targets or to enable optional features.
+
+### Required Protocols
+
+#### BlockIoProtocol
+
+The BlockIo protocol is required for loading system images from disk.
+If a target supports Fastboot mode, it is also used for writing images to disk.
+
+#### SimpleTextOutputProtocol
+
+The SimpleTextOutput protocol is used for logging
+and the text-based interface of Fastboot.
+On systems where there is no output functionality,
+this can be implemented as a series of no-op functions.
+
+### Conditionally Required Protocols
+
+#### RiscvBootProtocol
+
+Determines the boot hart ID which is then passed to the kernel.
+Only required for RISC-V targets.
+
+### Optional Protocols
+
+#### AndroidBootProtocol
+
+This is a custom protocol intended to provide
+specific functionality needed to boot Android.
+A full description is available [here](./EFI_ANDROID_BOOT_PROTOCOL.md).
+
+#### DevicePathProtocol
+
+The DevicePath protocol is a variable length binary structure
+made of variable length Device Path nodes.
+A handle representing a hardware resource is mapped
+to the protocol and provides specific data about that resource.
+
+If all three of DevicePath protocol, DevicePathToText protocol,
+and LoadedImage protocol are present, the GBL image path is logged
+to the console on load.
+
+This is a useful proof of concept for development to demonstrate
+that GBL is running and can interact with the UEFI environment.
+
+#### DevicePathToTextProtocol
+
+The DevicePathToText protocol converts device paths and nodes to text.
+
+#### LoadedImageProtocol
+
+The LoadedImage protocol can be used on the handle of an image to provide
+information about the image, including its device handle and device path.
+
+#### SimpleNetworkProtocol
+
+If present, the SimpleNetwork protocol is used to provide Fastboot over TCP.
+No other EFI protocols are required: GBL wraps SimpleNetwork to provide TCP.
+
+Note: for security reasons, Fastboot over TCP is only available in dev builds.
+
+#### SimpleTextInputProtocol
+
+TODO: remove this protocol
diff --git a/gbl/readme.bzl b/gbl/readme.bzl
index fe8f7c2..cc8bdc9 100644
--- a/gbl/readme.bzl
+++ b/gbl/readme.bzl
@@ -49,15 +49,29 @@ if [ ! -f $README ]; then
   exit 1
 fi
 
+ALL_INPUTS=$(echo ${INPUT} | sed 's/,/ /g')
+
 DOCLESS_PROTOCOLS=""
-PROTOCOLS=($(echo $INPUT | sed 's/,/ /g' | xargs grep -h -E 'impl ProtocolInfo for .* \\{' | awk '{print $4}' | sort))
+PROTOCOLS=($(grep -hE 'impl ProtocolInfo for .* \\{' ${ALL_INPUTS} | awk '{print $4}' | sort))
 for P in ${PROTOCOLS[@]}
 do
-  grep -Lq $P $README || DOCLESS_PROTOCOLS+="\n\t$P"
+  grep -Lq $P ${README} || DOCLESS_PROTOCOLS+="\n\t$P"
 done
 
 if [ ! -z "${DOCLESS_PROTOCOLS}" ]; then
-  echo "Missing documentation for protocol(s):$DOCLESS_PROTOCOLS"
+  echo -e "Missing documentation for protocol(s):$DOCLESS_PROTOCOLS"
+  exit 1
+fi
+
+UNUSED_PROTOCOLS=""
+README_PROTOCOLS=($(grep -P " ?.*?Protocol$" ${README} | awk '{print $NF}' | sort | uniq))
+for P in ${README_PROTOCOLS[@]}
+do
+  grep -qhE "impl ProtocolInfo for $P" ${ALL_INPUTS} || UNUSED_PROTOCOLS+="\n\t$P"
+done
+
+if [ ! -z "${UNUSED_PROTOCOLS}" ]; then
+  echo -e "Unused protocol(s) found in documentation:$UNUSED_PROTOCOLS"
   exit 1
 fi
 
diff --git a/gbl/tests/BUILD b/gbl/tests/BUILD
index fc44e64..e51b5cd 100644
--- a/gbl/tests/BUILD
+++ b/gbl/tests/BUILD
@@ -15,8 +15,7 @@
 test_suite(
     name = "tests",
     tests = [
-        # TODO(b/340322551): protocols are properly documented
-        # "@gbl//:readme_test",
+        "@gbl//:readme_test",
         "@gbl//libabr:libabr_tests",
         "@gbl//libbootconfig:libbootconfig_test",
         "@gbl//libbootimg:libbootimg_test",