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    Subject[PATCH v12 0/4] Introduce the for_each_set_clump macro
    This patchset introduces a new generic version of for_each_set_clump. 
    The previous version of for_each_set_clump8 used a fixed size 8-bit
    clump, but the new generic version can work with clump (n-bits) having
    size between 1 and BITS_PER_LONG inclusive. size less than 1 or more than
    BITS_PER_LONG causes undefined behaviour. The patchset utilizes the new
    macro in some GPIO drivers.

    The earlier 8-bit for_each_set_clump8 facilitated 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.

    But with the new for_each_set_clump the clump size can be different from 8 bits.
    Moreover, the clump can be split at word boundary in situations where word
    size is not multiple of clump size. Following are examples showing the working
    of new macro for clump sizes of 24 bits and 6 bits.

    Example 1:
    clump size: 24 bits, Number of clumps (or ports): 10
    bitmap stores the bit information from where successive clumps are retrieved.

    /* bitmap memory region */
    0x00aa0000ff000000; /* Most significant bits */
    0xaaaaaa0000ff0000;
    0x000000aa000000aa;
    0xbbbbabcdeffedcba; /* Least significant bits */

    Different iterations of for_each_set_clump:-
    'offset' is the bit position and 'clump' is the 24 bit clump from the
    above bitmap.
    Iteration first: offset: 0 clump: 0xfedcba
    Iteration second: offset: 24 clump: 0xabcdef
    Iteration third: offset: 48 clump: 0xaabbbb
    Iteration fourth: offset: 96 clump: 0xaa
    Iteration fifth: offset: 144 clump: 0xff
    Iteration sixth: offset: 168 clump: 0xaaaaaa
    Iteration seventh: offset: 216 clump: 0xff
    Loop breaks because in the end the remaining bits (0x00aa) size was less
    than clump size of 24 bits.

    In above example it can be seen that in iteration third, the 24 bit clump
    that was retrieved was split between bitmap[0] and bitmap[1]. This example
    also shows that 24 bit zeroes if present in between, were skipped (preserving
    the previous for_each_set_macro8 behaviour).

    Example 2:
    clump size = 6 bits, Number of clumps (or ports) = 3.

    /* bitmap memory region */
    0x00aa0000ff000000; /* Most significant bits */
    0xaaaaaa0000ff0000;
    0x0f00000000000000;
    0x0000000000000ac0; /* Least significant bits */

    Different iterations of for_each_set_clump:
    'offset' is the bit position and 'clump' is the 6 bit clump from the
    above bitmap.
    Iteration first: offset: 6 clump: 0x2b
    Loop breaks because 6 * 3 = 18 bits traversed in bitmap.
    Here 6 * 3 is clump size * no. of clumps.

    Changes in v12:
    - [Patch 1/4]: Format and modify comments.
    - [Patch 1/4]: Optimize code using '<<' operator with GENMASK.
    - [Patch 4/4]: Remove extra empty newline.

    Changes in v11:
    - [Patch 1/4]: Document range of values 'nbits' can take.
    - [Patch 4/4]: Change variable name 'flag' to 'flags'.

    Changes in v10:
    - Patchset based on v5.9-rc1.

    Changes in v9:
    - [Patch 4/4]: Remove looping of 'for_each_set_clump' and instead process two
    halves of a 64-bit bitmap separately or individually. Use normal spin_lock
    call for second inner lock. And take the spin_lock_init call outside the 'if'
    condition in the probe function of driver.

    Changes in v8:
    - [Patch 2/4]: Minor change: Use '__initdata' for correct section mismatch
    in 'clump_test_data' array.

    Changes in v7:
    - [Patch 2/4]: Minor changes: Use macro 'DECLARE_BITMAP()' and split 'struct'
    definition and test data.

    Changes in v6:
    - [Patch 2/4]: Make 'for loop' inside test_for_each_set_clump more
    succinct.

    Changes in v5:
    - [Patch 4/4]: Minor change: Hardcode value for better code readability.

    Changes in v4:
    - [Patch 2/4]: Use 'for' loop in test function of for_each_set_clump.
    - [Patch 3/4]: Minor change: Inline value for better code readability.
    - [Patch 4/4]: Minor change: Inline value for better code readability.

    Changes in v3:
    - [Patch 3/4]: Change datatype of some variables from u64 to unsigned long
    in function thunderx_gpio_set_multiple.

    CHanges in v2:
    - [Patch 2/4]: Unify different tests for 'for_each_set_clump'. Pass test data as
    function parameters.
    - [Patch 2/4]: Remove unnecessary bitmap_zero calls.

    Syed Nayyar Waris (4):
    bitops: Introduce the for_each_set_clump macro
    lib/test_bitmap.c: Add for_each_set_clump test cases
    gpio: thunderx: Utilize for_each_set_clump macro
    gpio: xilinx: Utilize generic bitmap_get_value and _set_value

    drivers/gpio/gpio-thunderx.c | 11 ++-
    drivers/gpio/gpio-xilinx.c | 65 +++++++-------
    include/asm-generic/bitops/find.h | 19 ++++
    include/linux/bitmap.h | 61 +++++++++++++
    include/linux/bitops.h | 13 +++
    lib/find_bit.c | 14 +++
    lib/test_bitmap.c | 144 ++++++++++++++++++++++++++++++
    7 files changed, 290 insertions(+), 37 deletions(-)


    base-commit: 9123e3a74ec7b934a4a099e98af6a61c2f80bbf5
    --
    2.26.2

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