[PATCH] Proposal for new GPIO API and example implementation for STM32F4 BSP

[oss at c-mauderer.de]

Hello Duc,

Am 29.06.22 um 13:46 schrieb Duc Doan:
> Hello Christian,
> 
> I have been writing the complete API and also implementation for
> STM32F4. A patch is coming soon.
> 
> On Mon, 2022-06-27 at 13:33 +0200, Christian MAUDERER wrote:
>> Regarding pin groups: I think it's worth to think a bit about how the
>> structure could be extended. You don't have to implement it right now
>> but you should have a plan what could be possible.
>>
>>   From my point of view, there are two directions how that could be
>> implemented: Masks or lists.
>>
>> If you have a mask (like 0x00108 for pin 3 and pin 8) it has the
>> advantage that it works fast for most controllers. Difficult is that
>> it
>> adds a limit to the maximum pin number depending on the size of the
>> mask. With that it works only for a few hardware models.
>>
>> The other option is to add a list of pins instead of a mask. That
>> makes
>> it inefficient because most controllers will have to collect pins
>> into
>> masks and work with that.
>>
>> Hm. Difficult. Maybe someone else has a good idea for that in the
>> next
>> few days.
> 
> I am thinking of later adding separate functions that handle pin
> groups. I think it's quite hard to integrate into current functions
> because of using virtual pin.
> 
> I have an assumption that needs confirmation: all microcontrollers (or
> most of them) have register size equal to word size, and pin masks
> should be at word size. Is that assumption correct? If so, maybe we can
> just use unsigned int (or uintptr_t) for pin masks?

Not sure whether some 64bit controllers don't use 32bit registers. So 
it's not generally true that registers have the word size. It should 
work for most controllers (at least the ones I worked with) but I 
wouldn't guarantee it.

Beneath that: You most likely know my argument already: What about I2C 
or SPI chips. They can use register sizes that are not the same as the 
controllers register size (even if they are most likely only 8 bit most 
of the time at least for I2C).

Best regards

Christian

> 
> Best,
> 
> Duc Doan
> 
>