Re: [PATCH V6] gpio: virtio: Add IRQ support

[Viresh Kumar <viresh.kumar@xxxxxxxxxx>]

On 21-10-21, 12:07, Geert Uytterhoeven wrote:
> On Thu, Oct 21, 2021 at 11:52 AM Viresh Kumar <viresh.kumar@xxxxxxxxxx> wrote:
> > The structure will get aligned to the size of largest element and each
> > element will be aligned to itself. I don't see how this will break
> > even in case of 32/64 bit communication.
> 
> Structures are not aligned to the size of the largest element, but
> to the largest alignment needed for each member.

Right, I was talking in terms of the structures we have here for GPIO.
The biggest member here (for any structure) is 32bits long, and
compiler shouldn't add extra padding here.

> This can be smaller than the size of the largest element.
> E.g. alignof(long long) might be 4, not 8. 

Right.

> And m68k aligns to two bytes at most.

Interesting, I assumed that it will be 4bytes for 32 bit systems. So
in case of m68k, we will see something like this ?

struct foo {
    u8 a;       // aligned to 2 bytes

                // padding of 1 byte

    u32 b;      // aligned to 2 bytes
}

-- 
viresh