Re: [PATCH v3 02/18] gpio: uapi: define uAPI v2
From: Bartosz Golaszewski
Date: Wed Aug 12 2020 - 13:49:07 EST
On Wed, Aug 12, 2020 at 3:55 AM Kent Gibson <warthog618@xxxxxxxxx> wrote:
> On Tue, Aug 11, 2020 at 09:11:41PM +0200, Bartosz Golaszewski wrote:
> > On Sun, Aug 9, 2020 at 3:26 PM Kent Gibson <warthog618@xxxxxxxxx> wrote:
> > >
> > >
> > > +/*
> > > + * Maximum number of requested lines.
> > > + *
> > > + * Must be no greater than 64 as bitmaps are limited to 64-bits, and a
> > > + * multiple of 2 to ensure 32/64-bit alignment of structs.
> > > + */
> > > +#define GPIO_V2_LINES_MAX 64
> > > +
> > If we refer to bitmaps for which helpers are defined in
> > include/linux/bitmap.h then they're not limited to 64-bits. I'd just
> > say here that we want to fit into 64-bit integers for simplicity.
> Strictly speaking, userspace doesn't know about include/linux/bitmap.h,
> but I'm happy to remove any ambiguity.
> Does this work for you?:
> * Must be no greater than 64, as bitmaps are restricted here to 64-bits
> * for simplicity, and a multiple of 2 to ensure 32/64-bit alignment of
> * structs.