linux-kernel - Re: [PATCH 01/21] NTB: correct missing readq/writeq errors

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Date:	Mon, 21 Jan 2013 10:23:45 -0800
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Jon Mason <jon.mason@...el.com>
Cc:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	Dave Jiang <dave.jiang@...el.com>,
	Nicholas Bellinger <nab@...ux-iscsi.org>
Subject: Re: [PATCH 01/21] NTB: correct missing readq/writeq errors

On Mon, Jan 21, 2013 at 10:38:18AM -0700, Jon Mason wrote:
> On Sun, Jan 20, 2013 at 03:40:05PM -0800, Greg KH wrote:
> > On Sat, Jan 19, 2013 at 02:02:15AM -0700, Jon Mason wrote:
> > > Atomic readq and writeq do not exist by default on some 32bit
> > > architectures, thus causing compile errors due to non-existent symbols.
> > > In those cases, use the definitions of those symbols from
> > > include/asm-generic/io-64-nonatomic-hi-lo.h
> > > 
> > > Signed-off-by: Jon Mason <jon.mason@...el.com>
> > > ---
> > >  drivers/ntb/ntb_hw.c |    1 +
> > >  1 file changed, 1 insertion(+)
> > > 
> > > diff --git a/drivers/ntb/ntb_hw.c b/drivers/ntb/ntb_hw.c
> > > index 4c71b17..0b46fef 100644
> > > --- a/drivers/ntb/ntb_hw.c
> > > +++ b/drivers/ntb/ntb_hw.c
> > > @@ -45,6 +45,7 @@
> > >   * Contact Information:
> > >   * Jon Mason <jon.mason@...el.com>
> > >   */
> > > +#include <asm-generic/io-64-nonatomic-hi-lo.h>
> > 
> > Really?  This seems really odd.  Usually we just don't build the code
> > for any platform that doesn't have readq/writeq.  Otherwise, shouldn't
> > those arches just include this file themselves to keep everything
> > working?  Individual drivers shouldn't have to do this.
> 
> There is no readq/writeq for 32bit x86.  I was using this header file
> to get around that.  I freely admit that I have done 0 testing on
> 32bit, but it should work.  If you prefer I modify the Kconfig to only
> enable this for x86_64 until such time as I test on x86_32, I will
> happily submit that patch.

No, other drivers on 32bit x86 also use readq, and do not include this
asm header file.  So there is a proper way to do this, just dig through
the header file include mess to determine the proper one to include.
You should never have to include asm-generic file directly, that's the
issue here.

thanks,

greg k-h
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