[Minios-devel] [UNIKRAFT PATCH 8/8] lib/uklibparam: Add documentation for parameters

[Sharan Santhanam <sharan.santhanam@xxxxxxxxx>]

This patch adds documentation for Unikraft library argument
library.

Signed-off-by: Sharan Santhanam <sharan.santhanam@xxxxxxxxx>
---
 doc/guides/developers-app.rst | 72 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 72 insertions(+)

diff --git a/doc/guides/developers-app.rst b/doc/guides/developers-app.rst
index 2a67b1f..fe779a4 100644
--- a/doc/guides/developers-app.rst
+++ b/doc/guides/developers-app.rst
@@ -323,6 +323,78 @@ An example context of extra.ld: ::
 
 This will add the section .uk_fs_list after the .text
 
+==================================
+Command line arguments in Unikraft
+==================================
+Unikraft command line arguments could either belong to an application or to a
+library. These two classes of arguments are separated by **--**. The
+arguments meant to a library precedes the **--**, followed by the application
+arguments.
+
+Pass an argument to a library
+-----------------------------
+Unikraft provides support to pass arguments of the following data type:
+
+========  ========================
+Type      Description
+========  ========================
+char      Single character value
+__s8      Same as char
+__u8      Single byte value
+__s16     Short signed integer
+__u16     Short unsigned integer
+int       Integer
+__s32     Signed integer
+__u32     Unsigned integer
+__s64     Signed long integer
+__u64     Unsigned long integer
+charp     C strings.
+========  ========================
+
+There are three interfaces through which a library registers with a variable
+with Unikraft. These are:
+
+* UK_LIB_PARAM     - Pass a scalar value of the above type to a variable.
+* UK_LIB_PARAM_STR - Pass a null terminated string to a variable.
+* UK_LIB_PARAM_ARR - Pass space separated list of values of the above type.
+
+Each library argument is identified by the following format ::
+
+ [library name].[variable name]
+
+ where,
+     library name is the name registered with Unikraft build system.
+     variable name is the name of the global or static variable in the program.
+
+Examples
+--------
+If the library requires command line argument support, it needs some
+configuration to be performed while building the library. A Unikraft library 
can
+be specific to a particular platform or common across all the platform.
+For the common library, one has to edit the Makefile.uk with ::
+
+ $(eval $(call addlib_paramprefix,libukalloc,alloc))
+ where,
+      libukalloc is the name of the library
+      alloc is the alias for the library name.
+
+or for the platform library, edit the Makefile.uk with ::
+
+ $(eval $(call addplatlib_paramprefix,linuxu,liblinuxuplat,linuxu))
+ where,
+     linuxu is the Unikraft platform
+     liblinuxuplat is the name of the library
+     linuxu an alias for the library name.
+
+As the next step, we define a variable and register it with the ``uk_libparam``
+library. The example below a simple code snippet ::
+
+ static __u32 heap_size = CONFIG_LINUXU_DEFAULT_HEAPMB;
+ UK_LIB_PARAM(heap_size, __u32);
+
+We can override the default value using the following command line ::
+
+  ./unikraft_linuxu-x86_64 linuxu.heap_size=10 --
 
 ============================
 Make Targets
-- 
2.7.4


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