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    SubjectRe: [PATCH v2 05/18] gpiolib: cdev: support GPIO_GET_LINE_IOCTL and GPIOLINE_GET_VALUES_IOCTL
    On Sun, Aug 2, 2020 at 5:32 AM Kent Gibson <warthog618@gmail.com> wrote:
    >
    > On Fri, Jul 31, 2020 at 06:05:10PM +0200, Bartosz Golaszewski wrote:
    > > On Sun, Jul 26, 2020 at 3:12 AM Kent Gibson <warthog618@gmail.com> wrote:

    [snip!]

    > > > >
    > > > > > +static u64 gpioline_config_flags(struct gpioline_config *lc, int line_idx)
    > > > > > +{
    > > > > > + int i;
    > > > > > +
    > > > > > + for (i = lc->num_attrs - 1; i >= 0; i--) {
    > > > >
    > > > > Much better to read is
    > > > >
    > > > > unsigned int i = lc->num_attrs;
    > > > >
    > > > > while (i--) {
    > > > > ...
    > > > > }
    > > > >
    > > >
    > > > Really? I find that the post-decrement in the while makes determining the
    > > > bounds of the loop more confusing.
    > > >
    > >
    > > Agreed, Andy: this is too much nit-picking. :)
    > >
    >
    > I was actually hoping for some feedback on the direction of that loop,
    > as it relates to the handling of multiple instances of the same
    > attribute associated with a given line.
    >
    > The reverse loop here implements a last in wins policy, but I'm now
    > thinking the kernel should be encouraging userspace to only associate a
    > given attribute with a line once, and that a first in wins would help do
    > that - as additional associations would be ignored.
    >
    > Alternatively, the kernel should enforce that an attribute can only be
    > associated once, but that would require adding more request validation.
    >

    I guess this would result in a lot of churn to do validation which is
    largely unnecessary? To me the first in wins sounds more consistent.

    Also: I just started going through the patches - nice idea with the
    GPIO attributes, I really like it. Although I need to give it a longer
    thought tomorrow - I'm wondering if we can maybe unify them and the
    flags.

    [snip]

    Bartosz

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