Thread (10 messages) flat view 10 messages, 5 authors, 2007-08-16

Re: [PATCH v2] powerpc: add setmaskedbits macros

From: Michael Ellerman <hidden>
Date: 2007-08-16 03:55:48

On Wed, 2007-08-15 at 16:30 -0500, Timur Tabi wrote:
quoted hunk ↗ jump to hunk
This patch adds the setmaskedbits_xxx() macros, which are used to set a
multiple-bit bit pattern in a register.  The macros include a mask, which
zeros the respective bits before applying the value via a bitwise-OR.
There are big-endian and little-endian versions for 8, 16, 32, and 64 bits.

These new macros are useful because the setbits macros can only be used 
to set single-bit fields.  For example, if you have a 32-bit register 
where bits 17-20 need to be set to 0100, you would do  
setmaskedbits_be32(p, 4 << 11, 0xF << 11).

Signed-off-by: Timur Tabi <redacted>
---

Updated the changelog to include a reason why you'd want these macros.
I have a number of new SOC device drivers coming up that will use these
macros, if this patch is accepted.

 include/asm-powerpc/io.h |   13 +++++++++++++
 1 files changed, 13 insertions(+), 0 deletions(-)
diff --git a/include/asm-powerpc/io.h b/include/asm-powerpc/io.h
index bb8d965..ac3defb 100644
--- a/include/asm-powerpc/io.h
+++ b/include/asm-powerpc/io.h
@@ -734,6 +734,19 @@ static inline void * bus_to_virt(unsigned long address)
 #define setbits16(_addr, _v) out_be16((_addr), in_be16(_addr) |  (_v))
 #define clrbits16(_addr, _v) out_be16((_addr), in_be16(_addr) & ~(_v))
 
+#ifdef __powerpc64__
+#define setmaskedbits_be64(a, v, m) out_be64((a), (in_be64(a) & ~(m)) | (v))
+#define setmaskedbits_le64(a, v, m) out_le64((a), (in_le64(a) & ~(m)) | (v))
+#endif
+
+#define setmaskedbits_be32(a, v, m) out_be32((a), (in_be32(a) & ~(m)) | (v))
+#define setmaskedbits_be16(a, v, m) out_be16((a), (in_be16(a) & ~(m)) | (v))
+
+#define setmaskedbits_le32(a, v, m) out_le32((a), (in_le32(a) & ~(m)) | (v))
+#define setmaskedbits_le16(a, v, m) out_le16((a), (in_le16(a) & ~(m)) | (v))
+
+#define setmaskedbits_8(a, v, m) out_8((a), (in_8(a) & ~(m)) | (v))
Can you extract the masking logic, rather than repeating it 7 times:

#define maskbits(a, v, m)	((a) & ~(m) | (v))

And if you're going to the trouble of making a macro, why not make it a
bit more useful and have it check that the value and the mask match, ie:

(v & ~m == 0)

Final random thought, you could make the size/endian an argument:

#define setmaskedbits(a, v, m, s)  out_##s((a), (in_##s(a) & ~(m) | (v))

cheers

-- 
Michael Ellerman
OzLabs, IBM Australia Development Lab

wwweb: http://michael.ellerman.id.au
phone: +61 2 6212 1183 (tie line 70 21183)

We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person

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