[PATCH] 6fire: Convert byte_rev_table uses to bitrev8

[PATCH] 6fire: Convert byte_rev_table uses to bitrev8

[Wang, Yalin]

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 <joe@perches.com>
Signed-off-by: Yalin Wang <yalin.wang@sonymobile.com>
---
 sound/usb/6fire/firmware.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/usb/6fire/firmware.c b/sound/usb/6fire/firmware.c
index 3b02e54..2e39c3f 100644
--- a/sound/usb/6fire/firmware.c
+++ b/sound/usb/6fire/firmware.c
@@ -316,7 +316,7 @@ static int usb6fire_fw_fpga_upload(
 
 	while (c != end) {
 		for (i = 0; c != end && i < FPGA_BUFSIZE; i++, c++)
-			buffer[i] = byte_rev_table[(u8) *c];
+			buffer[i] = bitrev8((u8) *c);
 
 		ret = usb6fire_fw_fpga_write(device, buffer, i);
 		if (ret < 0) {
-- 
2.1.1

Re: [PATCH] 6fire: Convert byte_rev_table uses to bitrev8

[Joe Perches]

On Fri, 2014-11-14 at 13:13 +0800, Wang, Yalin wrote:
> 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 <joe@perches.com>
> Signed-off-by: Yalin Wang <yalin.wang@sonymobile.com>
> ---
[]
> diff --git a/sound/usb/6fire/firmware.c b/sound/usb/6fire/firmware.c
[]
> @@ -316,7 +316,7 @@ static int usb6fire_fw_fpga_upload(
>  
>  	while (c != end) {
>  		for (i = 0; c != end && i < FPGA_BUFSIZE; i++, c++)
> -			buffer[i] = byte_rev_table[(u8) *c];
> +			buffer[i] = bitrev8((u8) *c);

This is not what I submitted.
What I posted did not have a space after (u8)

https://lkml.org/lkml/2014/10/28/1056

If you are going to resubmit or add your own sign-off,
please try to maintain the proper patch that is
submitted and please also use a "From:" line before
the patch itself.

Thanks, Joe

[PATCH RFC] arm/arm64:add CONFIG_HAVE_ARCH_BITREVERSE to support rbit

[Wang, Yalin]

this change add CONFIG_HAVE_ARCH_BITREVERSE config option,
so that we can use arm/arm64 rbit instruction to do bitrev operation
by hardware.

Signed-off-by: Yalin Wang <yalin.wang@sonymobile.com>
---
 arch/arm/Kconfig                |  1 +
 arch/arm/include/asm/bitrev.h   | 21 +++++++++++++++++++++
 arch/arm64/Kconfig              |  1 +
 arch/arm64/include/asm/bitrev.h | 21 +++++++++++++++++++++
 include/linux/bitrev.h          |  9 +++++++++
 lib/Kconfig                     |  8 ++++++++
 lib/bitrev.c                    |  2 ++
 7 files changed, 63 insertions(+)
 create mode 100644 arch/arm/include/asm/bitrev.h
 create mode 100644 arch/arm64/include/asm/bitrev.h

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 89c4b5c..426cbcc 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -16,6 +16,7 @@ config ARM
 	select DCACHE_WORD_ACCESS if HAVE_EFFICIENT_UNALIGNED_ACCESS
 	select GENERIC_ALLOCATOR
 	select GENERIC_ATOMIC64 if (CPU_V7M || CPU_V6 || !CPU_32v6K || !AEABI)
+	select HAVE_ARCH_BITREVERSE if (CPU_V7M || CPU_V7)
 	select GENERIC_CLOCKEVENTS_BROADCAST if SMP
 	select GENERIC_IDLE_POLL_SETUP
 	select GENERIC_IRQ_PROBE
diff --git a/arch/arm/include/asm/bitrev.h b/arch/arm/include/asm/bitrev.h
new file mode 100644
index 0000000..0df5866
--- /dev/null
+++ b/arch/arm/include/asm/bitrev.h
@@ -0,0 +1,21 @@
+#ifndef __ASM_ARM_BITREV_H
+#define __ASM_ARM_BITREV_H
+
+static inline __attribute_const__ u32 __arch_bitrev32(u32 x)
+{
+	__asm__ ("rbit %0, %1" : "=r" (x) : "r" (x));
+	return x;
+}
+
+static inline __attribute_const__ u16 __arch_bitrev16(u16 x)
+{
+	return __arch_bitrev32((u32)x) >> 16;
+}
+
+static inline __attribute_const__ u8 __arch_bitrev8(u8 x)
+{
+	return __arch_bitrev32((u32)x) >> 24;
+}
+
+#endif
+
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index ac9afde..a2566d7 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -35,6 +35,7 @@ config ARM64
 	select HARDIRQS_SW_RESEND
 	select HAVE_ARCH_AUDITSYSCALL
 	select HAVE_ARCH_JUMP_LABEL
+	select HAVE_ARCH_BITREVERSE
 	select HAVE_ARCH_KGDB
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_BPF_JIT
diff --git a/arch/arm64/include/asm/bitrev.h b/arch/arm64/include/asm/bitrev.h
new file mode 100644
index 0000000..5d24c11
--- /dev/null
+++ b/arch/arm64/include/asm/bitrev.h
@@ -0,0 +1,21 @@
+#ifndef __ASM_ARM_BITREV_H
+#define __ASM_ARM_BITREV_H
+
+static inline __attribute_const__ u32 __arch_bitrev32(u32 x)
+{
+	__asm__ ("rbit %w0, %w1" : "=r" (x) : "r" (x));
+	return x;
+}
+
+static inline __attribute_const__ u16 __arch_bitrev16(u16 x)
+{
+	return __arch_bitrev32((u32)x) >> 16;
+}
+
+static inline __attribute_const__ u8 __arch_bitrev8(u8 x)
+{
+	return __arch_bitrev32((u32)x) >> 24;
+}
+
+#endif
+
diff --git a/include/linux/bitrev.h b/include/linux/bitrev.h
index 7ffe03f..ef5b2bb 100644
--- a/include/linux/bitrev.h
+++ b/include/linux/bitrev.h
@@ -3,6 +3,14 @@
 
 #include <linux/types.h>
 
+#ifdef CONFIG_HAVE_ARCH_BITREVERSE
+#include <asm/bitrev.h>
+
+#define bitrev32 __arch_bitrev32
+#define bitrev16 __arch_bitrev16
+#define bitrev8 __arch_bitrev8
+
+#else
 extern u8 const byte_rev_table[256];
 
 static inline u8 bitrev8(u8 byte)
@@ -13,4 +21,5 @@ static inline u8 bitrev8(u8 byte)
 extern u16 bitrev16(u16 in);
 extern u32 bitrev32(u32 in);
 
+#endif /* CONFIG_HAVE_ARCH_BITREVERSE */
 #endif /* _LINUX_BITREV_H */
diff --git a/lib/Kconfig b/lib/Kconfig
index 54cf309..e0e0453 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -13,6 +13,14 @@ config RAID6_PQ
 config BITREVERSE
 	tristate
 
+config HAVE_ARCH_BITREVERSE
+	boolean
+	default n
+	help
+	  This option provides an config for the architecture which have instruction
+	  can do bitreverse operation, we use the hardware instruction if the architecture
+	  have this capability.
+
 config RATIONAL
 	boolean
 
diff --git a/lib/bitrev.c b/lib/bitrev.c
index 3956203..93d637a 100644
--- a/lib/bitrev.c
+++ b/lib/bitrev.c
@@ -1,3 +1,4 @@
+#ifndef CONFIG_HAVE_ARCH_BITREVERSE
 #include <linux/types.h>
 #include <linux/module.h>
 #include <linux/bitrev.h>
@@ -57,3 +58,4 @@ u32 bitrev32(u32 x)
 	return (bitrev16(x & 0xffff) << 16) | bitrev16(x >> 16);
 }
 EXPORT_SYMBOL(bitrev32);
+#endif /* CONFIG_HAVE_ARCH_BITREVERSE */
-- 
2.1.1

[RFC V2] arm/arm64:add CONFIG_HAVE_ARCH_BITREVERSE to support rbit instruction

[Wang, Yalin]

this change add CONFIG_HAVE_ARCH_BITREVERSE config option,
so that we can use arm/arm64 rbit instruction to do bitrev operation
by hardware.

Signed-off-by: Yalin Wang <yalin.wang@sonymobile.com>
---
 arch/arm/Kconfig                |  1 +
 arch/arm/include/asm/bitrev.h   | 21 +++++++++++++++++++++
 arch/arm64/Kconfig              |  1 +
 arch/arm64/include/asm/bitrev.h | 21 +++++++++++++++++++++
 include/linux/bitrev.h          |  9 +++++++++
 lib/Kconfig                     |  9 +++++++++
 lib/bitrev.c                    |  2 ++
 7 files changed, 64 insertions(+)
 create mode 100644 arch/arm/include/asm/bitrev.h
 create mode 100644 arch/arm64/include/asm/bitrev.h

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 89c4b5c..426cbcc 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -16,6 +16,7 @@ config ARM
 	select DCACHE_WORD_ACCESS if HAVE_EFFICIENT_UNALIGNED_ACCESS
 	select GENERIC_ALLOCATOR
 	select GENERIC_ATOMIC64 if (CPU_V7M || CPU_V6 || !CPU_32v6K || !AEABI)
+	select HAVE_ARCH_BITREVERSE if (CPU_V7M || CPU_V7)
 	select GENERIC_CLOCKEVENTS_BROADCAST if SMP
 	select GENERIC_IDLE_POLL_SETUP
 	select GENERIC_IRQ_PROBE
diff --git a/arch/arm/include/asm/bitrev.h b/arch/arm/include/asm/bitrev.h
new file mode 100644
index 0000000..0df5866
--- /dev/null
+++ b/arch/arm/include/asm/bitrev.h
@@ -0,0 +1,21 @@
+#ifndef __ASM_ARM_BITREV_H
+#define __ASM_ARM_BITREV_H
+
+static inline __attribute_const__ u32 __arch_bitrev32(u32 x)
+{
+	__asm__ ("rbit %0, %1" : "=r" (x) : "r" (x));
+	return x;
+}
+
+static inline __attribute_const__ u16 __arch_bitrev16(u16 x)
+{
+	return __arch_bitrev32((u32)x) >> 16;
+}
+
+static inline __attribute_const__ u8 __arch_bitrev8(u8 x)
+{
+	return __arch_bitrev32((u32)x) >> 24;
+}
+
+#endif
+
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 9532f8d..263c28c 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -36,6 +36,7 @@ config ARM64
 	select HARDIRQS_SW_RESEND
 	select HAVE_ARCH_AUDITSYSCALL
 	select HAVE_ARCH_JUMP_LABEL
+	select HAVE_ARCH_BITREVERSE
 	select HAVE_ARCH_KGDB
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_BPF_JIT
diff --git a/arch/arm64/include/asm/bitrev.h b/arch/arm64/include/asm/bitrev.h
new file mode 100644
index 0000000..5d24c11
--- /dev/null
+++ b/arch/arm64/include/asm/bitrev.h
@@ -0,0 +1,21 @@
+#ifndef __ASM_ARM_BITREV_H
+#define __ASM_ARM_BITREV_H
+
+static inline __attribute_const__ u32 __arch_bitrev32(u32 x)
+{
+	__asm__ ("rbit %w0, %w1" : "=r" (x) : "r" (x));
+	return x;
+}
+
+static inline __attribute_const__ u16 __arch_bitrev16(u16 x)
+{
+	return __arch_bitrev32((u32)x) >> 16;
+}
+
+static inline __attribute_const__ u8 __arch_bitrev8(u8 x)
+{
+	return __arch_bitrev32((u32)x) >> 24;
+}
+
+#endif
+
diff --git a/include/linux/bitrev.h b/include/linux/bitrev.h
index 7ffe03f..ef5b2bb 100644
--- a/include/linux/bitrev.h
+++ b/include/linux/bitrev.h
@@ -3,6 +3,14 @@
 
 #include <linux/types.h>
 
+#ifdef CONFIG_HAVE_ARCH_BITREVERSE
+#include <asm/bitrev.h>
+
+#define bitrev32 __arch_bitrev32
+#define bitrev16 __arch_bitrev16
+#define bitrev8 __arch_bitrev8
+
+#else
 extern u8 const byte_rev_table[256];
 
 static inline u8 bitrev8(u8 byte)
@@ -13,4 +21,5 @@ static inline u8 bitrev8(u8 byte)
 extern u16 bitrev16(u16 in);
 extern u32 bitrev32(u32 in);
 
+#endif /* CONFIG_HAVE_ARCH_BITREVERSE */
 #endif /* _LINUX_BITREV_H */
diff --git a/lib/Kconfig b/lib/Kconfig
index 54cf309..cd177ca 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -13,6 +13,15 @@ config RAID6_PQ
 config BITREVERSE
 	tristate
 
+config HAVE_ARCH_BITREVERSE
+	boolean
+	default n
+	depends on BITREVERSE
+	help
+	  This option provides an config for the architecture which have instruction
+	  can do bitreverse operation, we use the hardware instruction if the architecture
+	  have this capability.
+
 config RATIONAL
 	boolean
 
diff --git a/lib/bitrev.c b/lib/bitrev.c
index 3956203..93d637a 100644
--- a/lib/bitrev.c
+++ b/lib/bitrev.c
@@ -1,3 +1,4 @@
+#ifndef CONFIG_HAVE_ARCH_BITREVERSE
 #include <linux/types.h>
 #include <linux/module.h>
 #include <linux/bitrev.h>
@@ -57,3 +58,4 @@ u32 bitrev32(u32 x)
 	return (bitrev16(x & 0xffff) << 16) | bitrev16(x >> 16);
 }
 EXPORT_SYMBOL(bitrev32);
+#endif /* CONFIG_HAVE_ARCH_BITREVERSE */
-- 
2.1.1

Re: [RFC V2] arm/arm64:add CONFIG_HAVE_ARCH_BITREVERSE to support rbit instruction

[Joe Perches]

On Mon, 2014-10-27 at 14:37 +0800, Wang, Yalin wrote:
> this change add CONFIG_HAVE_ARCH_BITREVERSE config option,
> so that we can use arm/arm64 rbit instruction to do bitrev operation
> by hardware.
> 
> Signed-off-by: Yalin Wang <yalin.wang@sonymobile.com>
> ---
>  arch/arm/Kconfig                |  1 +
>  arch/arm/include/asm/bitrev.h   | 21 +++++++++++++++++++++
>  arch/arm64/Kconfig              |  1 +
>  arch/arm64/include/asm/bitrev.h | 21 +++++++++++++++++++++
>  include/linux/bitrev.h          |  9 +++++++++
>  lib/Kconfig                     |  9 +++++++++
>  lib/bitrev.c                    |  2 ++
>  7 files changed, 64 insertions(+)
>  create mode 100644 arch/arm/include/asm/bitrev.h
>  create mode 100644 arch/arm64/include/asm/bitrev.h
> 
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 89c4b5c..426cbcc 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -16,6 +16,7 @@ config ARM
>  	select DCACHE_WORD_ACCESS if HAVE_EFFICIENT_UNALIGNED_ACCESS
>  	select GENERIC_ALLOCATOR
>  	select GENERIC_ATOMIC64 if (CPU_V7M || CPU_V6 || !CPU_32v6K || !AEABI)
> +	select HAVE_ARCH_BITREVERSE if (CPU_V7M || CPU_V7)
>  	select GENERIC_CLOCKEVENTS_BROADCAST if SMP
>  	select GENERIC_IDLE_POLL_SETUP
>  	select GENERIC_IRQ_PROBE
> diff --git a/arch/arm/include/asm/bitrev.h b/arch/arm/include/asm/bitrev.h
> new file mode 100644
> index 0000000..0df5866
> --- /dev/null
> +++ b/arch/arm/include/asm/bitrev.h
> @@ -0,0 +1,21 @@
> +#ifndef __ASM_ARM_BITREV_H
> +#define __ASM_ARM_BITREV_H
> +
> +static inline __attribute_const__ u32 __arch_bitrev32(u32 x)
> +{
> +	__asm__ ("rbit %0, %1" : "=r" (x) : "r" (x));
> +	return x;
> +}
> +
> +static inline __attribute_const__ u16 __arch_bitrev16(u16 x)
> +{
> +	return __arch_bitrev32((u32)x) >> 16;
> +}
> +
> +static inline __attribute_const__ u8 __arch_bitrev8(u8 x)
> +{
> +	return __arch_bitrev32((u32)x) >> 24;
> +}
> +
> +#endif
> +
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 9532f8d..263c28c 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -36,6 +36,7 @@ config ARM64
>  	select HARDIRQS_SW_RESEND
>  	select HAVE_ARCH_AUDITSYSCALL
>  	select HAVE_ARCH_JUMP_LABEL
> +	select HAVE_ARCH_BITREVERSE
>  	select HAVE_ARCH_KGDB
>  	select HAVE_ARCH_TRACEHOOK
>  	select HAVE_BPF_JIT
> diff --git a/arch/arm64/include/asm/bitrev.h b/arch/arm64/include/asm/bitrev.h
> new file mode 100644
> index 0000000..5d24c11
> --- /dev/null
> +++ b/arch/arm64/include/asm/bitrev.h
> @@ -0,0 +1,21 @@
> +#ifndef __ASM_ARM_BITREV_H
> +#define __ASM_ARM_BITREV_H
> +
> +static inline __attribute_const__ u32 __arch_bitrev32(u32 x)
> +{
> +	__asm__ ("rbit %w0, %w1" : "=r" (x) : "r" (x));
> +	return x;
> +}
> +
> +static inline __attribute_const__ u16 __arch_bitrev16(u16 x)
> +{
> +	return __arch_bitrev32((u32)x) >> 16;
> +}
> +
> +static inline __attribute_const__ u8 __arch_bitrev8(u8 x)
> +{
> +	return __arch_bitrev32((u32)x) >> 24;
> +}
> +
> +#endif
> +
> diff --git a/include/linux/bitrev.h b/include/linux/bitrev.h
> index 7ffe03f..ef5b2bb 100644
> --- a/include/linux/bitrev.h
> +++ b/include/linux/bitrev.h
> @@ -3,6 +3,14 @@
>  
>  #include <linux/types.h>
>  
> +#ifdef CONFIG_HAVE_ARCH_BITREVERSE
> +#include <asm/bitrev.h>
> +
> +#define bitrev32 __arch_bitrev32
> +#define bitrev16 __arch_bitrev16
> +#define bitrev8 __arch_bitrev8
> +
> +#else
>  extern u8 const byte_rev_table[256];

If this is done, the direct uses of byte_rev_table in
drivers/net/wireless/ath/carl9170/phy.c and
sound/usb/6fire/firmware.c should be converted too?

[PATCH] 6fire: Convert byte_rev_table uses to bitrev8

[Joe Perches]

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 <joe@perches.com>
---
On Sun, 2014-10-26 at 23:46 -0700, Joe Perches wrote:
> On Mon, 2014-10-27 at 14:37 +0800, Wang, Yalin wrote:
> > this change add CONFIG_HAVE_ARCH_BITREVERSE config option,
> > so that we can use arm/arm64 rbit instruction to do bitrev operation
> > by hardware.
[]
> > diff --git a/include/linux/bitrev.h b/include/linux/bitrev.h
> > index 7ffe03f..ef5b2bb 100644
> > --- a/include/linux/bitrev.h
> > +++ b/include/linux/bitrev.h
> > @@ -3,6 +3,14 @@
> >  
> >  #include <linux/types.h>
> >  
> > +#ifdef CONFIG_HAVE_ARCH_BITREVERSE
> > +#include <asm/bitrev.h>
> > +
> > +#define bitrev32 __arch_bitrev32
> > +#define bitrev16 __arch_bitrev16
> > +#define bitrev8 __arch_bitrev8
> > +
> > +#else
> >  extern u8 const byte_rev_table[256];

 sound/usb/6fire/firmware.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/usb/6fire/firmware.c b/sound/usb/6fire/firmware.c
index 3b02e54..62c25e7 100644
--- a/sound/usb/6fire/firmware.c
+++ b/sound/usb/6fire/firmware.c
@@ -316,7 +316,7 @@ static int usb6fire_fw_fpga_upload(
 
 	while (c != end) {
 		for (i = 0; c != end && i < FPGA_BUFSIZE; i++, c++)
-			buffer[i] = byte_rev_table[(u8) *c];
+			buffer[i] = bitrev8((u8)*c);
 
 		ret = usb6fire_fw_fpga_write(device, buffer, i);
 		if (ret < 0) {

RE: [PATCH] 6fire: Convert byte_rev_table uses to bitrev8

[Wang, Yalin]

> 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 <joe@perches.com>
> ---
> On Sun, 2014-10-26 at 23:46 -0700, Joe Perches wrote:
> > On Mon, 2014-10-27 at 14:37 +0800, Wang, Yalin wrote:
> > > this change add CONFIG_HAVE_ARCH_BITREVERSE config option, so that
> > > we can use arm/arm64 rbit instruction to do bitrev operation by
> > > hardware.
> []
> > > diff --git a/include/linux/bitrev.h b/include/linux/bitrev.h index
> > > 7ffe03f..ef5b2bb 100644
> > > --- a/include/linux/bitrev.h
> > > +++ b/include/linux/bitrev.h
> > > @@ -3,6 +3,14 @@
> > >
> > >  #include <linux/types.h>
> > >
> > > +#ifdef CONFIG_HAVE_ARCH_BITREVERSE
> > > +#include <asm/bitrev.h>
> > > +
> > > +#define bitrev32 __arch_bitrev32
> > > +#define bitrev16 __arch_bitrev16
> > > +#define bitrev8 __arch_bitrev8
> > > +
> > > +#else
> > >  extern u8 const byte_rev_table[256];
> 
>  sound/usb/6fire/firmware.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/sound/usb/6fire/firmware.c b/sound/usb/6fire/firmware.c index
> 3b02e54..62c25e7 100644
> --- a/sound/usb/6fire/firmware.c
> +++ b/sound/usb/6fire/firmware.c
> @@ -316,7 +316,7 @@ static int usb6fire_fw_fpga_upload(
> 
>  	while (c != end) {
>  		for (i = 0; c != end && i < FPGA_BUFSIZE; i++, c++)
> -			buffer[i] = byte_rev_table[(u8) *c];
> +			buffer[i] = bitrev8((u8)*c);
> 
>  		ret = usb6fire_fw_fpga_write(device, buffer, i);
>  		if (ret < 0) {
> 
I think the most safe way is change byte_rev_table[] to be satic,
So that no driver can access it directly,
The build error can remind the developer if they use byte_rev_table[]
Directly .

Thanks

Re: [PATCH] 6fire: Convert byte_rev_table uses to bitrev8

[Joe Perches]

On Wed, 2014-10-29 at 10:42 +0800, Wang, Yalin wrote:
> > Use the inline function instead of directly indexing the array.
> > This allows some architectures with hardware instructions for bit reversals
> > to eliminate the array.
[]
> > On Sun, 2014-10-26 at 23:46 -0700, Joe Perches wrote:
> > > On Mon, 2014-10-27 at 14:37 +0800, Wang, Yalin wrote:
> > > > this change add CONFIG_HAVE_ARCH_BITREVERSE config option, so that
> > > > we can use arm/arm64 rbit instruction to do bitrev operation by
> > > > hardware.
[]
> I think the most safe way is change byte_rev_table[] to be satic,
> So that no driver can access it directly,
> The build error can remind the developer if they use byte_rev_table[]
> Directly .

You can do that with your later patch, but the
existing uses _must_ be converted first so you
don't break the build.

RE: [PATCH] 6fire: Convert byte_rev_table uses to bitrev8

[Wang, Yalin]

> From: Joe Perches [mailto:joe@perches.com]
> > I think the most safe way is change byte_rev_table[] to be satic, So
> > that no driver can access it directly, The build error can remind the
> > developer if they use byte_rev_table[] Directly .
> 
> You can do that with your later patch, but the existing uses _must_ be
> converted first so you don't break the build.
> 
> 
Yeah, I agree with you,
I will add this into my later patch.

Thanks