Re: [PATCH v7] arm: use built-in byte swap function - Russell King

From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Kim Phillips <kim.phillips@freescale.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Stephen Rothwell <sfr@canb.auug.org.au>
Cc: "Woodhouse, David" <david.woodhouse@intel.com>,
	Nicolas Pitre <nico@fluxnic.net>,
	Rusty Russell <rusty@rustcorp.com.au>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Daniel Santos <daniel.santos@pobox.com>,
	Borislav Petkov <bp@alien8.de>,
	David Rientjes <rientjes@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v7] arm: use built-in byte swap function
Date: Thu, 6 Jun 2013 23:12:34 +0100	[thread overview]
Message-ID: <20130606221234.GQ18614@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <20130523231336.GS18614@n2100.arm.linux.org.uk>

On Fri, May 24, 2013 at 12:13:36AM +0100, Russell King - ARM Linux wrote:
> On Thu, May 23, 2013 at 11:46:54AM -0500, Kim Phillips wrote:
> > Enable the compiler intrinsic for byte swapping on arch ARM.  This
> > allows the compiler to detect and be able to optimize out byte
> > swappings, and has a very modest benefit on vmlinux size (Linaro gcc
> > 4.8):
> > 
> >    text	   data	    bss	    dec	    hex	filename
> > 2840310	 123932	  61960	3026202	 2e2d1a	vmlinux-lart #orig
> > 2840152	 123932	  61960	3026044	 2e2c7c	vmlinux-lart #builtin-bswap
> > 
> > 6473120	 314840	5616016	12403976 bd4508	vmlinux-mxs #orig
> > 6472586	 314848	5616016	12403450 bd42fa	vmlinux-mxs #builtin-bswap
> > 
> > 7419872	 318372	 379556	8117800	 7bde28	vmlinux-imx_v6_v7 #orig
> > 7419170	 318364	 379556	8117090	 7bdb62	vmlinux-imx_v6_v7 #builtin-bswap
> > 
> > Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
> > Reviewed-by: Nicolas Pitre <nico@linaro.org>
> > Acked-by: David Woodhouse <David.Woodhouse@intel.com>
> > ---
> > resending as v6 appears to have fallen though the cracks.  Russell?
> 
> Please put it in the patch system (otherwise I do drop patches.)

(Added Arnd/SFR in case they have comments.)

So, we have a problem here - the kind which appears when people stuff
things into the -next tree which aren't destined for the next merge
window.  This is the relevant context from your patch, which is
against linux-next:

-                lib1funcs.o lib1funcs.S ashldi3.o ashldi3.S \
-                font.o font.c head.o misc.o $(OBJS)
+                lib1funcs.o lib1funcs.S ashldi3.o ashldi3.S bswapsdi2.o \
+                bswapsdi2.S font.o font.c head.o misc.o $(OBJS)

 # Make sure files are removed during clean
 extra-y       += piggy.gzip piggy.lzo piggy.lzma piggy.xzkern piggy.lz4 \
                                                               ^^^^^^^^^
-                lib1funcs.S ashldi3.S $(libfdt) $(libfdt_hdrs)
+                lib1funcs.S ashldi3.S bswapsdi2.S $(libfdt) $(libfdt_hdrs)

the underlined bit - piggy.lz4 for those who read mail with proportional
fonts.

That is not in any kernel I have, and if it _is_ something that is
destined for the next merge window, it should be in my tree as it's
a core ARM feature, not in some random other tree.

Short of hand-editing and manually applying the patch, a solution would
be to rebase it on a mainline kernel version, like -rc4, and resubmit
that version instead.  That will ultimately then give sfr a conflict
which should be trivial to resolve - and hopefully we'll find out who's
carrying the LZ4 patch and putting it into linux-next.