New Build System Status

[Sebastian Huber]

On 02/12/2019 23:24, Chris Johns wrote:
> On 2/12/19 5:42 pm, Sebastian Huber wrote:
>> On 01/12/2019 23:53, Chris Johns wrote:
>>> On 27/11/19 11:26 pm, Sebastian Huber wrote:
>>>> On 27/11/2019 13:17, Hesham Almatary wrote:
>>>>> On Wed, 27 Nov 2019 at 11:59, Sebastian Huber
>>>>> <sebastian.huber at embedded-brains.de>  wrote:
>>>>>> On 27/11/2019 12:49, Hesham Almatary wrote:
>>>>>>> Hi Sebastian,
>>>>>>>
>>>>>>> Thanks for that great effort. I'd aim to use this build system for my
>>>>>>> RISC-V development.
>>>>>>>
>>>>>>> I followed the user manual trying to build RISC-V targets and RTEMS
>>>>>>> (aaf7f8b84) and here are a few comments:
>>>>>>>
>>>>>>> * .waf bsp_defaults doesn't give an error when mistyping the BSP name,
>>>>>>> but just outputs an empty .ini file.
>>>>>> If there is no matching BSP, then you get nothing. I think this is the
>>>>>> right thing to do.
>>> If the user does not enter the correct BSP name we should provide an relevant
>>> error message on stderr and return a non-zero error code. I believe we should
>>> not silently move past an error without a clear indication there is a problem.
>> We are talking here about the "./waf bsp_defaults" command. I think it is
>> perfectly fine to output nothing if there is nothing to output. This is the
>> normal UNIX style. What happens if you grep for something which doesn't exits?
>> Anyway, I changed the command like this:
>>
>> $ ./waf bsp_defaults --rtems-specs=spec/build/cpukit
>> # The build specification contains no BSPs
>>
>> $ ./waf bsp_defaults --rtems-bsps=foobar,perfection
>> # No BSP matches with the specified patterns: 'foobar', 'perfection'
> Unix commands often cannot change because of the things users have built up
> around them. It does not mean what is provided is the right way. What we are
> discussing is going to be around a long time and we need to examine the detail
> so we can avoid breaking users with changes.
> 
> In the case of grep it's default if no file names are provided is to read
> string. I do not think it relates.
> 
> As I said before it makes scripting and tooling around the command problematic
> and complicated.

Could you please give an example, why the no output if there is nothing 
to output makes scripting and tooling complicated? If you search for the 
empty set you get it.

> 
>>>>>> Doing a
>>>>>>
>>>>>> ./waf bsp_defaults --rtems-bsps=riscv/rv64imac_medany  > bsps.ini
>>>>>>
>>>>>> is not a recommended use case. You should only set the necessary minimum
>>>>>> of options.
>>> If this documented?
>> Yes, but apparently not good enough. I will try to fix this.
> Great.
> 
>>>>> Not sure, I only wanted to build a specific BSP variant without having
>>>>> to build all variants. Is that not recommended?
>>>> This is fine, but I would not dump all options into the config.ini, maybe just:
>>>>
>>>> [riscv/rv64imac_medany]
>>>> COMPILER = clang
>>>> BUILD_TESTS = True
>>> How do you get a list of valid options and values to know what to set and not
>>> set?
>> You get the options with default values via "./waf bsp_defaults". You should
>> only set options for which you don't like the default value. For example, some
>> BSPs allow you to set the initial value of some registers, e.g.
>>
>> # initial BUCSR value
>> QORIQ_INITIAL_BUCSR = 0x01400201
>>
>> Lets suppose a chip errata appears and it says you have to set the undocumented
>> bit 31 to activate an errata workaround. You change the value in the build
>> specification to 0x81400201 in the RTEMS sources. Everyone who did a
>>
>> ./waf bsp_defaults --rtems-bsps=xxx  > config.ini
>>
>> will not profit from this bug fix.
> I understand this however my next question was ...
> 
>>> If you do not providing a value do you get your current version's default? Does
>>> this make updating defaults in rtems.git more complicated?
> Often a BSP is based on the developers set up and a specific project. This is a
> fair thing to do and I fine with that happening. A number of "defaults" are
> actually "settings" for a project. In the case of the example you give above if
> that register already has a local setting for another reason that RTEMS has not
> adopted you have a conflict that needs to be exposed and resolved. We will never
> achieve a unified set of defaults.

Ok, it seems there are counter examples for everything if it comes to 
BSP configuration.

> The issue I am attempting to address is present no matter what solution you
> provide. I am wondering if in time we need to add some sort of diff and conflict
> resolution tool so a user can see how they stand against the defaults in any
> release we make? We cannot solve the problem however we can provide a standard
> way our users can.

Adding a diff command would be easy, but I don't think we should 
overburden the new build system with features before it is in wide 
spread use. You can already do it with the existing command:

./waf bsp_defaults --rtems-bsps=somebsp > defaults.ini
diff -u myconfig.ini defaults.ini

-- 
Sebastian Huber, embedded brains GmbH

Address : Dornierstr. 4, D-82178 Puchheim, Germany
Phone   : +49 89 189 47 41-16
Fax     : +49 89 189 47 41-09
E-Mail  : sebastian.huber at embedded-brains.de
PGP     : Public key available on request.

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