FreeIPMI Coding

by 

Albert Chu
chu11@llnl.gov

These are some short descriptions on coding style, API style, other
thoughts for those interested in developing for FreeIPMI.

1) Code Style
-------------

The GNU coding style was selected for FreeIPMI.  Please try to follow
the coding style used in the rest of FreeIPMI.  Here's a short example
that covers the generics of the GNU coding style.

int
main(int argc, char **argv)
{
  int a = 0;
  int b = 1;

  if (a == 1)
    printf("yoda\n");

  if (a == 5
      || b == 1)
    {
      printf("foobar\n");
      printf("xyzzy\n");
    }

  while (a++ < 5)
    printf("lala\n");

  while (b++ < 7)
    {
      printf("blah\n");
      printf("garble\n");
    }
}

2) Parameter Checking
---------------------

Please carefully check the input parameters on the inputs your
program and/or functions take.  Minor parsing issues can lead to
catastrophic mistakes in IPMI.

For example, suppose you have a --power-control option that takes a
number to represent a type of operation (on, off, etc.).  Suppose a
user inputs "--power-control=foobar". The "foobar" will be read as a
'0' by strtoul().  If not properly checked, the '0' can be passed to
the IPMI Chassis Control command, which uses the '0' to power off a
node.

In programs, when appropriate, output error messages to the user
indicating that how and why the inputted parameters were incorrect.

3) Code Consistency
-------------------

Please keep your code as consistent as possible to other code in
FreeIPMI.  That includes code indenting style, brace style, API style,
and naming convention (which is discussed in more detail below).

Although there may be situations that a particular API style or naming
convention will make things easier for you and your code (such as
shortening the name of a function, decreasing the number of parameters
you need to pass to a function via a struct, etc.), we ask that your
code be consistent so that it does not confuse other developers.

If there is a distinct technical reason that you must use a different
API style, please bring it up with the FreeIPMI authors.

For example, pretty much all of the "fill" functions in libfreeipmi
take the exact parameters they need to fill the fiid object which is
passed along as a parameter.  All parameters are passed by value, not
by a pointer or other method (e.g. object, struct, etc.).

Exceptions do exist.  For example, fill_cmd_chassis_identify() takes
parameters passed by pointer instead of passed by value.  The reason
is that both fields are optional and need not be filled according to
the IPMI specification.  The pointer gives the caller the ability to
set values (by passing a valid pointer) or not (by passing NULL).

4) Libfreeipmi naming/function parameter conventions
----------------------------------------------------

The naming style in libfreeipmi was developed primarily for the
purpose of readability when code is being compared to the IPMI
specification.

Due to the size of the IPMI spec, there will be a lot of code.  In
earlier versions of FreeIPMI, there was confusion on where code was
located, what parameters were called, how parameters should be input,
etc. due to different people using different abbreviations styles,
putting functions out of order with the spec, in different files,
using/not-using different bitmasks, etc.  The code has been auditted
and cleaned up since then.

So when adding new functions/templates/parameters/files/etc. to
libfreeipmi, please name them consistently to the rest of the
libfreeipmi library and the IPMI specification.

This includes:
- naming functions/templates/parameters/files based on the spec
- in most cases, not abbreviating any words (or using consistent
  abbreviations in the rest of the library, check first!)
- matching parameter lists to the templates and in the same order
- ordering functions/templates/parameters/files/etc. consistently with the spec.

For example: 

ipmi-messaging-support-cmds.c

is the file for messaging support commands, chapter 22 of the IPMI 2.0 spec.

tmpl_cmd_get_channel_authentication_capabilities_rq
tmpl_cmd_get_channel_authentication_capabilities_rs

are the templates for the Get Channel Authentication Capapilities
command.

fiid_template_t tmpl_cmd_get_channel_authentication_capabilities_rq =
  {
    { 8, "cmd", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 4, "channel_number", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 3, "reserved1", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 1, "get_ipmi_v2.0_extended_data", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 4, "maximum_privilege_level", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 4, "reserved2", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 0, "", 0}
  };

fiid_template_t tmpl_cmd_get_channel_authentication_capabilities_rs =
  {
    { 8,  "cmd", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED | FIID_FIELD_MAKES_PACKET_SUFFICIENT},
    { 8,  "comp_code", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED | FIID_FIELD_MAKES_PACKET_SUFFICIENT},
    { 8,  "channel_number", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 1,  "authentication_type.none", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 1,  "authentication_type.md2", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 1,  "authentication_type.md5", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 1,  "authentication_type.reserved1", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 1,  "authentication_type.straight_password_key", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 1,  "authentication_type.oem_prop", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 1,  "authentication_type.reserved2", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 1,  "authentication_type.ipmi_v2.0_extended_capabilities_available", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 1,  "authentication_status.anonymous_login", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 1,  "authentication_status.null_username", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 1,  "authentication_status.non_null_username", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 1,  "authentication_status.user_level_authentication", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 1,  "authentication_status.per_message_authentication", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 1,  "authentication_status.k_g", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 2,  "authentication_status.reserved", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 1,  "channel_supports_ipmi_v1.5_connections", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 1,  "channel_supports_ipmi_v2.0_connections", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 6,  "reserved", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 24, "oem_id", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 8,  "oem_auxiliary_data", FIID_FIELD_REQUIRED | FIID_FIELD_LENGTH_FIXED},
    { 0, "", 0}
  };

The fields listed in the templates above directly match table 22-15,
the Get Channel Authentication Capabilities request and response
commands.

int fill_cmd_get_channel_authentication_capabilities (uint8_t channel_number,
                                                      uint8_t maximum_privilege_level,
                                                      fiid_obj_t obj_cmd_rq);

The function above matches the naming and takes exactly the parameters
needed by the Get Channel Authentication Capabilities request
template.

The coding conditions specified above may lead to function names or
function parameters names that exceed the 80 column mark or having
very long parameter lists.  We accept this annoyance (or poor coding
style, we admit it), as we consider matching the specification as a
more important need in libfreeipmi.

For example: 

int
fill_cmd_set_lan_configuration_parameters_authentication_type_enables (uint8_t channel_number,
                                                                       uint8_t callback_level_none,
                                                                       uint8_t callback_level_md2,
                                                                       uint8_t callback_level_md5,
                                                                       uint8_t callback_level_straight_password,
                                                                       uint8_t callback_level_oem_proprietary,
                                                                       uint8_t user_level_none,
                                                                       uint8_t user_level_md2,
                                                                       uint8_t user_level_md5,
                                                                       uint8_t user_level_straight_password,
                                                                       uint8_t user_level_oem_proprietary,
                                                                       uint8_t operator_level_none,
                                                                       uint8_t operator_level_md2,
                                                                       uint8_t operator_level_md5,
                                                                       uint8_t operator_level_straight_password,
                                                                       uint8_t operator_level_oem_proprietary,
                                                                       uint8_t admin_level_none,
                                                                       uint8_t admin_level_md2,
                                                                       uint8_t admin_level_md5,
                                                                       uint8_t admin_level_straight_password,
                                                                       uint8_t admin_level_oem_proprietary,
                                                                       uint8_t oem_level_none,
                                                                       uint8_t oem_level_md2,
                                                                       uint8_t oem_level_md5,
                                                                       uint8_t oem_level_straight_password,
                                                                       uint8_t oem_level_oem_proprietary,
                                                                       fiid_obj_t obj_cmd_rq);

The function name and parameters look pretty long and terrible.  But
the names and fields exactly match the get authentication type enables
fields listed in Table 23-4.  There should be very little difficulty
understanding what this funciton does, how it should be called, and
what the parameters are if you are reading along with the spec.

Because we want the code to match the IPMI spec as closely as
possible, we currently accept the code inefficiencies (due to large
stacks of parameters) that come with having long parameters lists and
the atrocities of having gigantic 25+ parameter function calls in
code.

