Re: [PATCH V6 1/2] virtio-gpio: Add the device specification

[Viresh Kumar <viresh.kumar@linaro.org>]

On Tue, 27 Jul 2021 at 19:47, Viresh Kumar <viresh.kumar@linaro.org> wrote:

> It is also important to mention here that in my current example, there
> was no copy
> of the gpio line name string made anywhere.
>
> If we choose this message to be per-line, then there will be at least one memcpy
> at the host of the string for each GPIO line, there may be another
> copy somewhere
> in between at guest or host, not sure. Though in case of a single
> request, this will
> be a single memcpy operation at the guest (and others in between as
> mentioned earlier),
> but not per line and maybe more efficient.
>
> So even in the best possible scenario, this will be several ms, at
> least for separate
> message for each GPIO line.
>
> Anyway, how do you suggest I define this call now. Per-line or entire
> block (fixed size or
> from config structure) ? I will do it the way you suggest to cut short
> the discussion :)

Also to mention that this request will always be called (at least for Linux)
only once for all the GPIO lines, at probe time only. And never after that.

So making it per-line doesn't give us any flexibility that we may be
looking for.

--
Viresh