[RFC 3/4] dtoc: add support for generate stuct udevice_id

[Walter Lozano]

Hi Simon,

On 26/7/20 11:53, Simon Glass wrote:
> Hi Walter,
>
> On Tue, 7 Jul 2020 at 08:08, Walter Lozano <walter.lozano at collabora.com> wrote:
>> Hi Simon
>>
>> On 6/7/20 16:21, Simon Glass wrote:
>>> Hi Walter,
>>>
>>> On Fri, 19 Jun 2020 at 15:12, Walter Lozano <walter.lozano at collabora.com> wrote:
>>>> Based on several reports there is an increasing concern in the impact
>>>> of adding additional features to drivers based on compatible strings.
>>>> A good example of this situation is found in [1].
>>>>
>>>> In order to reduce this impact and as an initial step for further
>>>> reduction, propose a new way to declare compatible strings, which allows
>>>> to only include the useful ones.
>>> What are the useful ones?
>> The useful ones would be those that are used by the selected DTB by the
>> current configuration. The idea of this patch is to declare all the
>> possible compatible strings in a way that dtoc can generate code for
>> only those which are going to be used, and in this way avoid lots of
>> #ifdef like the ones shows in
>>
>> http://patchwork.ozlabs.org/project/uboot/patch/20200525202429.2146-1-agust@denx.de/
>>
>>
>>>> The idea is to define compatible strings in a way to be easily parsed by
>>>> dtoc, which will be responsible to build struct udevice_id [] based on
>>>> the compatible strings present in the dtb.
>>>>
>>>> Additional features can be easily added, such as define constants
>>>> depending on the presence of compatible strings, which allows to enable
>>>> code blocks only in such cases without the need of adding additional
>>>> configuration options.
>>>>
>>>> [1] http://patchwork.ozlabs.org/project/uboot/patch/20200525202429.2146-1-agust@denx.de/
>>>>
>>>> Signed-off-by: Walter Lozano <walter.lozano at collabora.com>
>>>> ---
>>>>    tools/dtoc/dtb_platdata.py | 32 ++++++++++++++++++++++++++++++++
>>>>    1 file changed, 32 insertions(+)
>>> I think dtoc should be able to parse the compatible strings as they
>>> are today - e.g. see the tiny-dm stuff.
>>
>> Yes, I agree. My idea is that dtoc parses compatible strings as they are
>> today but also in this new way. The reason for this is to allow dtoc to
>> generate the code to include the useful compatible strings. Of course,
>> this only makes sense if the idea of generating the compatible string
>> associated  code is accepted.
>>
>> What do you think?
> I think this is useful and better than using #ifdef in the source code
> for this sort of thing. We need a way to specify the driver_data value
> as well, right?

Yes, I agree, it is better than #ifdef and c/ould give us some extra 
functionality.

What doe you mean by driver_data value? Are you referring to the data 
field? like

static struct esdhc_soc_data usdhc_imx7d_data = {
         .flags = ESDHC_FLAG_USDHC | ESDHC_FLAG_STD_TUNING
                         | ESDHC_FLAG_HAVE_CAP1 | ESDHC_FLAG_HS200
                         | ESDHC_FLAG_HS400,
};

If that is the case, I was thinking in defining a constant when specific 
compatible strings are enabled by dtoc, based in the above case

#ifdef FSL_ESDHC_IMX_V2
static struct esdhc_soc_data usdhc_imx7d_data = {
         .flags = ESDHC_FLAG_USDHC | ESDHC_FLAG_STD_TUNING
                         | ESDHC_FLAG_HAVE_CAP1 | ESDHC_FLAG_HS200
                         | ESDHC_FLAG_HS400,
};
#endif

COMPATIBLE(FSL_ESDHC, "fsl,imx7d-usdhc", &usdhc_imx7d_data, FSL_ESDHC_IMX_V2)

So when dtoc parses COMPATIBLE and determines that compatible 
"fsl,imx7d-usdhc" should be added it also defines FSL_ESDHC_IMX_V2.

This is alsoAs I comment you in the tread about tiny-dm I think that we 
can save some space following your suggestions, and for instance implement


> Re naming, perhaps DT_COMPAT() might be better than COMPATIBLE()? Or
> even a name that indicates that it is optional, like DT_OPT_COMPAT() ?
>
I totally agree, naming is very important, and DT_COMPAT() is much better.

What I don't fully understand is what are the cases for DT_OPT_COMPAT(), 
could you please clarify?

Regards,

Walter