Messages in this thread | | | Date | Thu, 3 Sep 2020 16:09:09 +0800 | From | Kent Gibson <> | Subject | Re: [PATCH v6 09/20] gpiolib: cdev: support edge detection for uAPI v2 |
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On Thu, Sep 03, 2020 at 09:55:22AM +0200, Bartosz Golaszewski wrote: > On Mon, Aug 31, 2020 at 5:22 AM Kent Gibson <warthog618@gmail.com> wrote: > > > > Add support for edge detection to lines requested using > > GPIO_V2_GET_LINE_IOCTL. > > > > The edge_detector implementation is based on the v1 lineevent > > implementation. > >
[snip]
> > + * close in time as possible to the actual event. > > + */ > > + line->timestamp = ktime_get_ns(); > > + > > + if (lr->num_lines != 1) > > + line->req_seqno = atomic_inc_return(&lr->seqno); > > Do we never increase req_seqno for a single line? >
For a single line we just use line_seqno for both to avoid the atomic_inc here and so reduce the time spent in the ISR and any SMP sync overheads.
As per the comment in struct linereq: * @seqno: the sequence number for edge events generated on all lines in * this line request. Note that this is not used when @num_lines is 1, as * the line_seqno is then the same and is cheaper to calculate.
Cheers, Kent.
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