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    Subject[PATCH 5.4 112/138] staging: comedi: ni_6527: fix INSN_CONFIG_DIGITAL_TRIG support
    Date
    From: Ian Abbott <abbotti@mev.co.uk>

    commit f07804ec77d77f8a9dcf570a24154e17747bc82f upstream.

    `ni6527_intr_insn_config()` processes `INSN_CONFIG` comedi instructions
    for the "interrupt" subdevice. When `data[0]` is
    `INSN_CONFIG_DIGITAL_TRIG` it is configuring the digital trigger. When
    `data[2]` is `COMEDI_DIGITAL_TRIG_ENABLE_EDGES` it is configuring rising
    and falling edge detection for the digital trigger, using a base channel
    number (or shift amount) in `data[3]`, a rising edge bitmask in
    `data[4]` and falling edge bitmask in `data[5]`.

    If the base channel number (shift amount) is greater than or equal to
    the number of channels (24) of the digital input subdevice, there are no
    changes to the rising and falling edges, so the mask of channels to be
    changed can be set to 0, otherwise the mask of channels to be changed,
    and the rising and falling edge bitmasks are shifted by the base channel
    number before calling `ni6527_set_edge_detection()` to change the
    appropriate registers. Unfortunately, the code is comparing the base
    channel (shift amount) to the interrupt subdevice's number of channels
    (1) instead of the digital input subdevice's number of channels (24).
    Fix it by comparing to 32 because all shift amounts for an `unsigned
    int` must be less than that and everything from bit 24 upwards is
    ignored by `ni6527_set_edge_detection()` anyway.

    Fixes: 110f9e687c1a8 ("staging: comedi: ni_6527: support INSN_CONFIG_DIGITAL_TRIG")
    Cc: <stable@vger.kernel.org> # 3.17+
    Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
    Link: https://lore.kernel.org/r/20200717145257.112660-2-abbotti@mev.co.uk
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/staging/comedi/drivers/ni_6527.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/drivers/staging/comedi/drivers/ni_6527.c
    +++ b/drivers/staging/comedi/drivers/ni_6527.c
    @@ -332,7 +332,7 @@ static int ni6527_intr_insn_config(struc
    case COMEDI_DIGITAL_TRIG_ENABLE_EDGES:
    /* check shift amount */
    shift = data[3];
    - if (shift >= s->n_chan) {
    + if (shift >= 32) {
    mask = 0;
    rising = 0;
    falling = 0;

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