[RFC V6 2/3] arm:add bitrev.h file to support rbit instruction
Russell King - ARM Linux
linux at arm.linux.org.uk
Thu Nov 13 16:17:21 PST 2014
On Thu, Nov 13, 2014 at 04:05:30PM -0800, Joe Perches wrote:
> On Thu, 2014-11-13 at 23:53 +0000, Russell King - ARM Linux wrote:
> > On Fri, Oct 31, 2014 at 01:42:44PM +0800, Wang, Yalin wrote:
> > > This patch add bitrev.h file to support rbit instruction,
> > > so that we can do bitrev operation by hardware.
> > > Signed-off-by: Yalin Wang <yalin.wang at sonymobile.com>
> > > ---
> > > arch/arm/Kconfig | 1 +
> > > arch/arm/include/asm/bitrev.h | 21 +++++++++++++++++++++
> > > 2 files changed, 22 insertions(+)
> > > create mode 100644 arch/arm/include/asm/bitrev.h
> > >
> > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> > > index 89c4b5c..be92b3b 100644
> > > --- a/arch/arm/Kconfig
> > > +++ b/arch/arm/Kconfig
> > > @@ -28,6 +28,7 @@ config ARM
> > > select HANDLE_DOMAIN_IRQ
> > > select HARDIRQS_SW_RESEND
> > > select HAVE_ARCH_AUDITSYSCALL if (AEABI && !OABI_COMPAT)
> > > + select HAVE_ARCH_BITREVERSE if (CPU_V7M || CPU_V7)
> > Looking at this, this is just wrong. Take a moment to consider what
> > happens if we build a kernel which supports both ARMv6 _and_ ARMv7 CPUs.
> > What happens if an ARMv6 CPU tries to execute an rbit instruction?
> > Second point (which isn't obvious from your submissions on-list) is that
> > you've loaded the patch system up with patches for other parts of the
> > kernel tree for which I am not responsible for. As such, I can't take
> > those patches without the sub-tree maintainer acking them. Also, the
> > commit text in those patches look weird:
> > 6fire: Convert byte_rev_table uses to bitrev8
> > Use the inline function instead of directly indexing the array.
> > This allows some architectures with hardware instructions for bit
> > reversals to eliminate the array.
> > Signed-off-by: Joe Perches <(address hidden)>
> > Signed-off-by: Yalin Wang <(address hidden)>
> > Why is Joe signing off on these patches?
> > Shouldn't his entry be an Acked-by: ?
> I didn't sign off on or ack the "add bitrev.h" patch.
Correct, I never said you did. Please read my message a bit more carefully
next time, huh?
> I created 2 patches that converted direct uses of byte_rev_table
> to that bitrev8 static inline. One of them is already in -next
> 7a1283d8f5298437a454ec477384dcd9f9f88bac carl9170: Convert byte_rev_table uses to bitrev8
> The other hasn't been applied.
> Maybe Takashi Iwai will get around to it one day.
Great, so I can just discard these that were incorrectly submitted to me
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