Re: [RFC] libgpiod public API reviews needed

[Bartosz Golaszewski <brgl@xxxxxxxx>]

2018-01-22 12:12 GMT+01:00 Arnd Bergmann <arnd@xxxxxxxx>:
> On Mon, Jan 22, 2018 at 12:02 PM, Bartosz Golaszewski <brgl@xxxxxxxx> wrote:
>> 2018-01-22 10:25 GMT+01:00 Arnd Bergmann <arnd@xxxxxxxx>:
>>>
>>> - on x86, the structures are incompatible between 32-bit and 64-bit
>>>   user space, as the former has no padding.
>>
>> Is this really an issue? Do distros really ship the same bytecode for
>> 32 and 64 bit architecures? I have never run into such problems
>> despite having used different python bindings for C libraries (I'm not
>> sure however how many of them dealt with any visible C structs).
>
> It's a huge issue, yes. You should be able to run an 32-bit distro
> or just a standalone 32-bit binary with a 64-bit kernel. This driver
> is otherwise written carefully to allow that, and it will work on all
> other architectures AFAICT, just not on x86.
>

Besides using struct timespec, I have other structs in gpiod.h which
would pose problems for ctypes-based python bindings - for example
struct gpiod_line_request_config which contains a pointer (C string).
If instead of using ctypes, I'd just use python's C extension modules,
is there any other trap caused by different data layout between 32 and
64 bit architectures that I should be aware of?

Also: if python bindings are the only victim of that - I'm ok with
timespec. It's up to bindings to provide a correct interface after
all, isn't it?

Best regards,
Bartosz Golaszewski
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