linux-kernel - Re: [RFC 08/11] gpiolib: cdev: Add hardware timestamp clock type

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Date:   Sun, 27 Jun 2021 13:38:10 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Dipen Patel <dipenp@...dia.com>
Cc:     "thierry.reding@...il.com" <thierry.reding@...il.com>,
        Jon Hunter <jonathanh@...dia.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-tegra <linux-tegra@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Kent Gibson <warthog618@...il.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>
Subject: Re: [RFC 08/11] gpiolib: cdev: Add hardware timestamp clock type

On Sat, Jun 26, 2021 at 1:48 AM Dipen Patel <dipenp@...dia.com> wrote:

> This patch adds new clock type for the GPIO controller which can
> timestamp gpio lines using hardware means. To expose such
> functionalities to the userspace, code has been added in this patch
> where during line create call, it checks for new clock type and if
> requested, calls hardware timestamp related API from gpiolib.c.
> During line change event, it retrieves timestamp in nano seconds by
> calling gpiod_get_hw_timestamp API from gpiolib.c. At the line release,
> it disables this functionality by calling gpiod_hw_timestamp_control.
>
> Signed-off-by: Dipen Patel <dipenp@...dia.com>

This looks good to me, pretty much exactly as I imagine it should be
done, and it is also nice that we only implement it
for the v2 UAPI.

Yours,
Linus Walleij