From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: "Thomas Petazzoni" <thomas.petazzoni@free-electrons.com>,
"Noralf Trønnes" <noralf@tronnes.org>,
driverdevel <devel@driverdev.osuosl.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] staging: fbtft: Disable DMA support if DMA is not available
Date: Fri, 24 Apr 2015 09:17:44 +0200 [thread overview]
Message-ID: <20150424071744.GA6146@kroah.com> (raw)
In-Reply-To: <CAMuHMdU5L_bdWWsnbrVobdTwzJRTwz2m3UawHp-1GXqyXu=hXg@mail.gmail.com>
On Fri, Apr 24, 2015 at 09:15:00AM +0200, Geert Uytterhoeven wrote:
> On Thu, Apr 23, 2015 at 9:17 PM, Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> > On Thu, Apr 23, 2015 at 08:47:15PM +0200, Geert Uytterhoeven wrote:
> >> If NO_DMA=y:
> >>
> >> drivers/built-in.o: In function `fbtft_framebuffer_alloc':
> >> (.text+0xb53cae): undefined reference to `dmam_alloc_coherent'
> >>
> >> As DMA support is already optional, make it depend on HAS_DMA.
> >>
> >> If !HAS_DMA, "dma" will always be false, and the compiler will optimize
> >> away the call to dmam_alloc_coherent().
> >
> > Oh that's "sneaky" and not good, let's just make this driver be
> > dependant on DMA and be done with it. I don't like to rely on the
> > optimizer to get things to work properly.
>
> Alternatively, I can stick in one more #ifdef, to no longer rely on the compiler
> optimization?
That would be better.
thanks,
greg k-h
prev parent reply other threads:[~2015-04-24 7:17 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-23 18:47 [PATCH v2] staging: fbtft: Disable DMA support if DMA is not available Geert Uytterhoeven
2015-04-23 19:17 ` Greg Kroah-Hartman
2015-04-24 7:15 ` Geert Uytterhoeven
2015-04-24 7:17 ` Greg Kroah-Hartman [this message]
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