linux-kernel - Re: [RFC][PATCH] kernel.h: Add generic roundup

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Message-ID: <20190524112656.5ef67c6c@gandalf.local.home>
Date:   Fri, 24 May 2019 11:26:56 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Roger Willcocks <roger@...mlight.ltd.uk>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ben Skeggs <bskeggs@...hat.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Leon Romanovsky <leon@...nel.org>,
        Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        linux-xfs@...r.kernel.org,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        nouveau@...ts.freedesktop.org,
        linux-rdma <linux-rdma@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC][PATCH] kernel.h: Add generic roundup_64() macro

On Fri, 24 May 2019 16:11:14 +0100
Roger Willcocks <roger@...mlight.ltd.uk> wrote:

> On 23/05/2019 16:27, Steven Rostedt wrote:
> >
> > I haven't yet tested this, but what about something like the following:
> >
> > ...perhaps forget about the constant check, and just force
> > the power of two check:
> >
> > 							\
> > 	if (!(__y & (__y >> 1))) {			\
> > 		__x = round_up(x, y);			\
> > 	} else {					\  
> 
> You probably want
> 
>             if (!(__y & (__y - 1))
> 
> --

Yes I do. I corrected it in my next email.

 http://lkml.kernel.org/r/20190523133648.591f9e78@gandalf.local.home

> #define roundup(x, y) (					\
> {							\
> 	typeof(y) __y = y;				\
> 	typeof(x) __x;					\
> 							\
> 	if (__y & (__y - 1))				\
> 		__x = round_up(x, __y);			\
> 	else						\
> 		__x = (((x) + (__y - 1)) / __y) * __y;	\
> 	__x;						\
> })


-- Steve