linux-kernel - Re: [PATCH] drm/radeon: silence GCC warning on 32 bit

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Message-ID: <20140221082021.GG22574@ulmo.nvidia.com>
Date:	Fri, 21 Feb 2014 09:20:22 +0100
From:	Thierry Reding <thierry.reding@...il.com>
To:	Paul Bolle <pebolle@...cali.nl>
Cc:	Ilia Mirkin <imirkin@...m.mit.edu>,
	Alex Deucher <alexander.deucher@....com>,
	Christian König <christian.koenig@....com>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/radeon: silence GCC warning on 32 bit

On Thu, Feb 20, 2014 at 10:24:53PM +0100, Paul Bolle wrote:
> On Thu, 2014-02-20 at 16:07 -0500, Ilia Mirkin wrote:
> > On Thu, Feb 20, 2014 at 4:02 PM, Paul Bolle <pebolle@...cali.nl> wrote:
> > > @@ -935,7 +935,7 @@ static ssize_t radeon_ttm_gtt_read(struct file *f, char __user *buf,
> > >         while (size) {
> > >                 loff_t p = *pos / PAGE_SIZE;
> > >                 unsigned off = *pos & ~PAGE_MASK;
> > > -               ssize_t cur_size = min(size, PAGE_SIZE - off);
> > > +               ssize_t cur_size = min(size, (size_t)(PAGE_SIZE - off));
> > 
> > Isn't the usual way of dealing with these to do something like
> > 
> > ssize_t cur_size = min_t(ssize_t, size, PAGE_SIZE - off)
> 
> I wouldn't know. I did
>     $ git grep -n "(size_t)(PAGE_SIZE"
>     arch/powerpc/mm/dma-noncoherent.c:357:  size_t seg_size = min((size_t)(PAGE_SIZE - offset), size);
>     arch/tile/kernel/pci-dma.c:176: size_t bytes = min(size, (size_t)(PAGE_SIZE - offset));
>     arch/tile/kernel/pci-dma.c:192: size_t bytes = min(size, (size_t)(PAGE_SIZE - offset));
>     drivers/net/wireless/ti/wlcore/main.c:806:      len = min(maxlen, (size_t)(PAGE_SIZE - wl->fwlog_size));
>     drivers/scsi/libfc/fc_libfc.c:143:                             (size_t)(PAGE_SIZE - (off & ~PAGE_MASK)));
>     drivers/target/tcm_fc/tfc_io.c:160:                     tlen = min(tlen, (size_t)(PAGE_SIZE -
>     drivers/target/tcm_fc/tfc_io.c:311:             tlen = min(tlen, (size_t)(PAGE_SIZE -
> 
> and concluded my solution was acceptable. Is your alternative considered
> to be better?

Yes, min_t() is specifically meant for this type of situation. On a side
note, I think cur_size should be size_t rather than ssize_t.

Thierry

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