[PATCH v14 00/11] Introduce the for_each_set_clump8 macro

William Breathitt Gray
2019-03-29T03:03:30Z

Changes in v14:
- Redefine bitmap_get_value8, bitmap_set_value8, and find_next_clump8
as static inline functions
- Rename 'idx' variable to 'index' in the bitmap_get_value8 and
bitmap_set_value8 functions
- Remove superfluous parens in gen_74x164_set_multiple

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 (11):
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
gpio: 74x164: Utilize the for_each_set_clump8 macro
thermal: intel: intel_soc_dts_iosf: Utilize for_each_set_clump8 macro

drivers/gpio/gpio-104-dio-48e.c | 73 ++++----------
drivers/gpio/gpio-104-idi-48.c | 36 ++-----
drivers/gpio/gpio-74x164.c | 19 ++--
drivers/gpio/gpio-gpio-mm.c | 73 ++++----------
drivers/gpio/gpio-pci-idio-16.c | 75 +++++---------
drivers/gpio/gpio-pcie-idio-24.c | 109 ++++++++-------------
drivers/gpio/gpio-uniphier.c | 16 ++-
drivers/gpio/gpio-ws16c48.c | 73 ++++----------
drivers/thermal/intel/intel_soc_dts_iosf.c | 29 +++---
drivers/thermal/intel/intel_soc_dts_iosf.h | 2 -
include/asm-generic/bitops/find.h | 61 ++++++++++++
include/linux/bitops.h | 5 +
lib/test_bitmap.c | 65 ++++++++++++
13 files changed, 299 insertions(+), 337 deletions(-)

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2.21.0