linux-kernel - [PATCH v2 0/7] Introduce the for_each_set_port

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Message-Id: <cover.1525785532.git.vilhelm.gray@gmail.com>
Date:   Tue,  8 May 2018 09:26:34 -0400
From:   William Breathitt Gray <vilhelm.gray@...il.com>
To:     linus.walleij@...aro.org
Cc:     linux-gpio@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        William Breathitt Gray <vilhelm.gray@...il.com>
Subject: [PATCH v2 0/7] Introduce the for_each_set_port_word macro

Changes in v2:
  - Include linux/types.h file in bitops/find.h to define size_t

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_port_word macro and utilizes
it in several GPIO drivers. The for_each_set_port_word macro facilitates
a for-loop syntax that iterates over entire groups of set bits at a
time.

For example, suppose you would like to iterate over a 16-bit integer 4
bits at a time, skipping over 4-bit groups with no set bit, where XXXX
represents the current 4-bit group:

    Example:        1011 1110 0000 1111
    First loop:     1011 1110 0000 XXXX
    Second loop:    1011 XXXX 0000 1111
    Third loop:     XXXX 1110 0000 1111

Each iteration of the loop returns the next 4-bit group that has at
least one set bit.

The for_each_set_port_word macro has six parameters:

    * port_word: set to current port word index for the iteration
    * word_index: set to current bitmap word index for the iteration
    * word_offset: bits offset of the found port word in the bitmap word
    * bits: bitmap to search within
    * size: bitmap size in number of port words
    * port_size: port word size in number of bits

The port_size argument can be an arbitrary number of bits and is not
required to be a multiple of 2.

I've called the group of bits a "port word" which may be a confusing
naming convention; I was afraid calling that them a "group" may be too
vague. Should a different name be chosen; what would you suggest?

This patchset was rebased on top of the following three commits:

    * commit aaf96e51de11 ("gpio: pci-idio-16: Fix port memory offset for get_multiple callback")
    * commit 304440aa96c6 ("gpio: pcie-idio-24: Fix port memory offset for get_multiple/set_multiple callbacks")
    * commit e026646c178d ("gpio: pcie-idio-24: Fix off-by-one error in get_multiple loop")

William Breathitt Gray

William Breathitt Gray (7):
  bitops: Introduce the for_each_set_port_word macro
  gpio: 104-dio-48e: Utilize for_each_set_port_word macro
  gpio: 104-idi-48: Utilize for_each_set_port_word macro
  gpio: gpio-mm: Utilize for_each_set_port_word macro
  gpio: ws16c48: Utilize for_each_set_port_word macro
  gpio: pci-idio-16: Utilize for_each_set_port_word macro
  gpio: pcie-idio-24: Utilize for_each_set_port_word macro

 drivers/gpio/gpio-104-dio-48e.c   |  67 +++++---------------
 drivers/gpio/gpio-104-idi-48.c    |  32 ++--------
 drivers/gpio/gpio-gpio-mm.c       |  67 +++++---------------
 drivers/gpio/gpio-pci-idio-16.c   |  67 ++++++--------------
 drivers/gpio/gpio-pcie-idio-24.c  | 102 +++++++++++-------------------
 drivers/gpio/gpio-ws16c48.c       |  66 +++++--------------
 include/asm-generic/bitops/find.h |  26 ++++++++
 include/linux/bitops.h            |   9 +++
 lib/find_bit.c                    |  28 ++++++++
 9 files changed, 172 insertions(+), 292 deletions(-)

-- 
2.17.0