Re: [PATCH net-next v7 01/19] lib/bitmap.c: conversion routines to/from u32 array

thanks. done in v8 I am sending right now.

On Mon, Feb 8, 2016 at 3:36 PM, Andrew Morton [off-list ref] wrote:

On Sun,  7 Feb 2016 17:08:45 -0800 David Decotigny [off-list ref] wrote:

quoted

From: David Decotigny <redacted>

Aimed at transferring bitmaps to/from user-space in a 32/64-bit agnostic
way.

Tested:
  unit tests (next patch) on qemu i386, x86_64, ppc, ppc64 BE and LE,
  ARM.

@@ -1060,6 +1062,90 @@ int bitmap_allocate_region(unsigned long *bitmap, unsigned int pos, int order)
 EXPORT_SYMBOL(bitmap_allocate_region);

 /**
+ * bitmap_from_u32array - copy the contents of a u32 array of bits to bitmap
+ *   @bitmap: array of unsigned longs, the destination bitmap, non NULL
+ *   @nbits: number of bits in @bitmap
+ *   @buf: array of u32 (in host byte order), the source bitmap, non NULL
+ *   @nwords: number of u32 words in @buf
+ *
+ * copy min(nbits, 32*nwords) bits from @buf to @bitmap, remaining
+ * bits between nword and nbits in @bitmap (if any) are cleared. In
+ * last word of @bitmap, the bits beyond nbits (if any) are kept
+ * unchanged.
+ */

This will leave the caller not knowing how many valid bits are actually
present in the resulting bitmap.  To determine that, the caller will
need to perform (duplicated) math on `nbits' and `nwords'.

quoted

+void bitmap_from_u32array(unsigned long *bitmap, unsigned int nbits,
+                       const u32 *buf, unsigned int nwords)

So how about we make this return the number of valid bits in *bitmap?

quoted

+/**
+ * bitmap_to_u32array - copy the contents of bitmap to a u32 array of bits
+ *   @buf: array of u32 (in host byte order), the dest bitmap, non NULL
+ *   @nwords: number of u32 words in @buf
+ *   @bitmap: array of unsigned longs, the source bitmap, non NULL
+ *   @nbits: number of bits in @bitmap
+ *
+ * copy min(nbits, 32*nwords) bits from @bitmap to @buf. Remaining
+ * bits after nbits in @buf (if any) are cleared.
+ */
+void bitmap_to_u32array(u32 *buf, unsigned int nwords,
+                     const unsigned long *bitmap, unsigned int nbits)

Ditto.