| Message ID | 1414531369.10912.14.camel@perches.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
> 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
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.
> 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
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) {