[PATCH v9 0/9] Introduce the for_each_set_clump8 macro

From: William Breathitt Gray
Date: Sun Mar 03 2019 - 02:44:35 EST

Changes in v9:
- Return unsigned long for bitmap_get_value8 for consistency

While adding GPIO get_multiple/set_multiple callback support for various
drivers, I noticed a pattern of looping manifesting that would be useful
standardized as a macro.

This patchset introduces the for_each_set_clump8 macro and utilizes it
in several GPIO drivers. The for_each_set_clump macro8 facilitates a
for-loop syntax that iterates over a memory region entire groups of set
bits at a time.

For example, suppose you would like to iterate over a 32-bit integer 8
bits at a time, skipping over 8-bit groups with no set bit, where
XXXXXXXX represents the current 8-bit group:

Example: 10111110 00000000 11111111 00110011
First loop: 10111110 00000000 11111111 XXXXXXXX
Second loop: 10111110 00000000 XXXXXXXX 00110011
Third loop: XXXXXXXX 00000000 11111111 00110011

Each iteration of the loop returns the next 8-bit group that has at
least one set bit.

The for_each_set_clump8 macro has four parameters:

* start: set to the bit offset of the current clump
* clump: set to the current clump value
* bits: bitmap to search within
* size: bitmap size in number of bits

In this version of the patchset, the for_each_set_clump macro has been
reimplemented and simplified based on the suggestions provided by Rasmus
Villemoes and Andy Shevchenko in the version 4 submission.

In particular, the function of the for_each_set_clump macro has been
restricted to handle only 8-bit clumps; the drivers that use the
for_each_set_clump macro only handle 8-bit ports so a generic
for_each_set_clump implementation is not necessary. Thus, a solution for
large clumps (i.e. those larger than the width of a bitmap word) can be
postponed until a driver appears that actually requires such a generic
for_each_set_clump implementation.

For what it's worth, a semi-generic for_each_set_clump (i.e. for clumps
smaller than the width of a bitmap word) can be implemented by simply
replacing the hardcoded '8' and '0xFF' instances with respective
variables. I have not yet had a need for such an implementation, and
since it falls short of a true generic for_each_set_clump function, I
have decided to forgo such an implementation for now.

In addition, the bitmap_get_value8 and bitmap_set_value8 functions are
introduced to get and set 8-bit values respectively. Their use is based
on the behavior suggested in the patchset version 4 review.

William Breathitt Gray (9):
bitops: Introduce the for_each_set_clump8 macro
lib/test_bitmap.c: Add for_each_set_clump8 test cases
gpio: 104-dio-48e: Utilize for_each_set_clump8 macro
gpio: 104-idi-48: Utilize for_each_set_clump8 macro
gpio: gpio-mm: Utilize for_each_set_clump8 macro
gpio: ws16c48: Utilize for_each_set_clump8 macro
gpio: pci-idio-16: Utilize for_each_set_clump8 macro
gpio: pcie-idio-24: Utilize for_each_set_clump8 macro
gpio: uniphier: Utilize for_each_set_clump8 macro

drivers/gpio/gpio-104-dio-48e.c | 73 ++++++--------------
drivers/gpio/gpio-104-idi-48.c | 37 +++-------
drivers/gpio/gpio-gpio-mm.c | 73 ++++++--------------
drivers/gpio/gpio-pci-idio-16.c | 75 ++++++++------------
drivers/gpio/gpio-pcie-idio-24.c | 111 +++++++++++-------------------
drivers/gpio/gpio-uniphier.c | 16 ++---
drivers/gpio/gpio-ws16c48.c | 72 ++++++-------------
include/asm-generic/bitops/find.h | 14 ++++
include/linux/bitops.h | 5 ++
lib/find_bit.c | 81 ++++++++++++++++++++++
lib/test_bitmap.c | 65 +++++++++++++++++
11 files changed, 313 insertions(+), 309 deletions(-)