yocto-kernel: add support for printing kernel feature descriptions

Add a yocto-kernel command allowing users to print the description and
compatibility of a given kernel feature.

(From meta-yocto rev: 73b4f1a8d156af6810cdde3af672d6286a7071e7)

Signed-off-by: Tom Zanussi <tom.zanussi@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/lib/bsp/help.py

@@ -387,6 +387,7 @@ yocto_kernel_usage = """
    feature add       Have a BSP use a feature
    feature rm        Have a BSP stop using a feature
    features list     List the features available to BSPs
+   feature describe  Describe a particular feature
 
  See 'yocto-kernel help COMMAND' for more information on a specific command.
 
@@ -723,6 +724,34 @@ DESCRIPTION
 """
 
 
+yocto_kernel_feature_describe_usage = """
+
+ Print the description and compatibility information for a given kernel feature
+
+ usage: yocto-kernel feature describe <bsp-name> [/xxxx/yyyy/feature.scc ...]
+
+ This command prints the description and compatibility of a specific
+ feature in the format 'description [compatibility].
+"""
+
+
+yocto_kernel_feature_describe_help = """
+
+NAME
+    yocto-kernel feature describe - print the description and
+    compatibility information for a given kernel feature
+
+SYNOPSIS
+    yocto-kernel feature describe <bsp-name> [/xxxx/yyyy/feature.scc ...]
+
+DESCRIPTION
+    This command prints the description and compatibility of a
+    specific feature in the format 'description [compatibility].  If
+    the feature doesn't define a description or compatibility, a
+    string with generic unknown values will be printed.
+"""
+
+
 ##
 # yocto-layer help and usage strings
 ##

scripts/lib/bsp/kernel.py

@@ -758,6 +758,56 @@ def yocto_kernel_available_features_list(scripts_path, machine):
     print_feature_descs(layer, "features")
 
 
+def find_feature_desc_url(git_url, feature):
+    """
+    Find the url of the kernel feature in the kernel repo specified
+    from the BSP's kernel recipe SRC_URI.
+    """
+    feature_desc_url = ""
+    if git_url.startswith("git://"):
+        git_url = git_url[len("git://"):].strip()
+        s = git_url.split("/")
+        if s[1].endswith(".git"):
+            s[1] = s[1][:len(s[1]) - len(".git")]
+        feature_desc_url = "http://" + s[0] + "/cgit/cgit.cgi/" + s[1] + \
+            "/plain/meta/cfg/kernel-cache/" + feature + "?h=meta"
+
+    return feature_desc_url
+
+
+def get_feature_desc(git_url, feature):
+    """
+    Return a feature description of the form 'description [compatibility]
+    BSPs, as gathered from the set of feature sources.
+    """
+    feature_desc_url = find_feature_desc_url(git_url, feature)
+    feature_desc_cmd = "wget -q -O - " + feature_desc_url
+    tmp = subprocess.Popen(feature_desc_cmd, shell=True, stdout=subprocess.PIPE).stdout.read()
+
+    return find_feature_desc(tmp.split("\n"))
+
+
+def yocto_kernel_feature_describe(scripts_path, machine, feature):
+    """
+    Display the description of a specific kernel feature available for
+    use in a BSP.
+    """
+    layer = find_bsp_layer(scripts_path, machine)
+
+    kernel = find_current_kernel(layer, machine)
+    if not kernel:
+        print "Couldn't determine the kernel for this BSP, exiting."
+        sys.exit(1)
+
+    context = create_context(machine, "arch", scripts_path)
+    context["name"] = "name"
+    context["filename"] = kernel
+    giturl = find_giturl(context)
+
+    desc = get_feature_desc(giturl, feature)
+
+    print desc
+
     
 def base_branches(context):
     """

scripts/yocto-kernel

@@ -243,6 +243,29 @@ def yocto_kernel_available_features_list_subcommand(args, usage_str):
     yocto_kernel_available_features_list(scripts_path, args[0])
 
 
+def yocto_kernel_feature_describe_subcommand(args, usage_str):
+    """
+    Command-line handling for listing the description of a specific
+    kernel feature available for use in a BSP.  This includes the
+    features present in the meta branch(es) of the pointed-to repo(s)
+    as well as the local features added in recipe-space to the current
+    BSP as well.  The real work is done by
+    bsp.kernel.yocto_kernel_feature_describe().
+    """
+    logging.debug("yocto_kernel_feature_describe_subcommand")
+
+    parser = optparse.OptionParser(usage = usage_str)
+
+    (options, args) = parser.parse_args(args)
+
+    if len(args) != 2:
+        logging.error("Wrong number of arguments, exiting\n")
+        parser.print_help()
+        sys.exit(1)
+
+    yocto_kernel_feature_describe(scripts_path, args[0], args[1])
+
+
 subcommands = {
     "config-list": [yocto_kernel_config_list_subcommand,
                     yocto_kernel_config_list_usage,
@@ -274,6 +297,9 @@ subcommands = {
     "features-list": [yocto_kernel_available_features_list_subcommand,
                  yocto_kernel_available_features_list_usage,
                  yocto_kernel_available_features_list_help],
+    "feature-describe": [yocto_kernel_feature_describe_subcommand,
+                 yocto_kernel_feature_describe_usage,
+                 yocto_kernel_feature_describe_help],
 }