Re: [libgpiod][PATCH] treewide: rework struct gpiod_line_bulk

[Bartosz Golaszewski <brgl@xxxxxxxx>]

On Fri, Oct 23, 2020 at 12:24 PM Andy Shevchenko
<andy.shevchenko@xxxxxxxxx> wrote:
>
> On Fri, Oct 23, 2020 at 12:31 PM Bartosz Golaszewski <brgl@xxxxxxxx> wrote:
> >

[snip]

>
> > +struct gpiod_line_bulk {
> > +       struct gpiod_chip *owner;
> > +       unsigned int num_lines;
> > +       unsigned int max_lines;
> > +       struct gpiod_line *lines[1];
>
> Why not '[]' as we do in the kernel?
>

Because I want to be able to store a single line in this structure if I do:

    struct gpiod_line_bulk bulk;

Using [] makes the size of this structure not take into account the
last array member.

> > +};
>
> > +#define BULK_SINGLE_LINE_INIT(line) \
> > +               { gpiod_line_get_chip(line), 1, 1, { (line) } }
>
> Hmm... Perhaps union can help here?
>
> union {
>   struct *lines[];
>   struct *line;
> }
>
> num_lines == 1 exactly defines this.
>

Nope because gcc will scream:

error: flexible array member in union

Bartosz