From: Alexandre Courbot <gnurou@gmail.com>
To: Linus Walleij <linus.walleij@linaro.org>
Cc: Chen-Yu Tsai <wens@csie.org>,
Mika Westerberg <mika.westerberg@linux.intel.com>,
Heikki Krogerus <heikki.krogerus@linux.intel.com>,
Arnd Bergmann <arnd@arndb.de>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
Johannes Berg <johannes@sipsolutions.net>,
"David S. Miller" <davem@davemloft.net>,
devicetree <devicetree@vger.kernel.org>,
netdev <netdev@vger.kernel.org>,
linux-wireless <linux-wireless@vger.kernel.org>,
linux-sunxi <linux-sunxi@googlegroups.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Maxime Ripard <maxime.ripard@free-electrons.com>
Subject: Re: [PATCH RFC 4/6] net: rfkill: gpio: add device tree support
Date: Tue, 21 Jan 2014 12:11:06 +0900 [thread overview]
Message-ID: <CAAVeFuLP4MkfXGG1FMauvUw_J63zRXdhGwxqYy5W98L1wCQNbw@mail.gmail.com> (raw)
In-Reply-To: <CACRpkdZOD4zeA8T5kbJ4c5NsnuzHCg1mw8rRMYNT9c4R-Qnc6A@mail.gmail.com>
On Sat, Jan 18, 2014 at 8:11 AM, Linus Walleij <linus.walleij@linaro.org> wrote:
> On Fri, Jan 17, 2014 at 6:43 PM, Chen-Yu Tsai <wens@csie.org> wrote:
>> On Sat, Jan 18, 2014 at 12:47 AM, Arnd Bergmann <arnd@arndb.de> wrote:
>
>>>> +- NAME_shutdown-gpios : GPIO phandle to shutdown control
>>>> + (phandle must be the second)
>>>> +- NAME_reset-gpios : GPIO phandle to reset control
>>>> +
>>>> +NAME must match the rfkill-name property. NAME_shutdown-gpios or
>>>> +NAME_reset-gpios, or both, must be defined.
>>>> +
>>>
>>> I don't understand this part. Why do you include the name in the
>>> gpios property, rather than just hardcoding the property strings
>>> to "shutdown-gpios" and "reset-gpios"?
>>
>> This quirk is a result of how gpiod_get_index implements device tree
>> lookup.
>
> Why can't it just have a single property "gpios", where the first
> element is the reset GPIO and the second is the shutdown GPIO?
>
> rfkill-gpio does this:
>
> gpio = devm_gpiod_get_index(&pdev->dev, rfkill->reset_name, 0);
> gpio = devm_gpiod_get_index(&pdev->dev, rfkill->shutdown_name, 1);
>
> The passed con ID name parameter is only there for the device
> tree case it seems. (ACPI ignores it.) So what about you just
> don't pass it at all and patch it to do like this instead:
>
> gpio = devm_gpiod_get_index(&pdev->dev, NULL, 0);
> gpio = devm_gpiod_get_index(&pdev->dev, NULL, 1);
>
> Heikki, are you OK with this change?
>
> I think this is actually necessary if the ACPI and DT unification
> pipe dream shall limp forward, we cannot have arguments passed
> that have a semantic effect on DT but not on ACPI... Drivers
> that are supposed to use both ACPI and DT will always
> have to pass NULL as con ID.
I agree that's how it should be be done with the current API if your
driver can obtain GPIOs from both ACPI and DT. This is a potential
issue, as drivers are not supposed to make assumptions about who is
going to be their GPIO provider. Let's say you started a driver with
only DT in mind, and used gpio_get(dev, con_id) to get your GPIOs. DT
bindings are thus of the form "con_id-gpio = <phandle>", and set in
stone. Then later, someone wants to use your driver with ACPI. How do
you handle that gracefully?
I'm starting to wonder, now that ACPI is a first-class GPIO provider,
whether we should not start to encourage the deprecation of the
"con_id-gpio = <phandle>" binding form in DT and only use a single
indexed GPIO property per device. The con_id parameter would then only
be used as a label, which would also have the nice side-effect that
all GPIOs used for a given function will be reported under the same
name no matter what the GPIO provider is.
>From an aesthetic point of view, I definitely prefer using con_id to
identify GPIOs instead of indexes, but I don't see how we can make it
play nice with ACPI. Thoughts?
Alex.
next prev parent reply other threads:[~2014-01-21 3:11 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-17 6:47 [PATCH RFC 0/6] net: rfkill: gpio: Add device tree support Chen-Yu Tsai
[not found] ` <1389941251-32692-1-git-send-email-wens-jdAy2FN1RRM@public.gmane.org>
2014-01-17 6:47 ` [PATCH RFC 1/6] net: rfkill: gpio: fix gpio name buffer size off by 1 Chen-Yu Tsai
2014-01-17 9:46 ` David Laight
[not found] ` <063D6719AE5E284EB5DD2968C1650D6D45EA9D-VkEWCZq2GCInGFn1LkZF6NBPR1lH4CV8@public.gmane.org>
2014-01-17 9:59 ` Chen-Yu Tsai
2014-01-17 6:47 ` [PATCH RFC 2/6] net: rfkill: gpio: use clk_prepare_enable/clk_disable_unprepare Chen-Yu Tsai
2014-01-17 6:47 ` [PATCH RFC 3/6] net: rfkill: gpio: fix reversed clock enable state Chen-Yu Tsai
2014-01-17 6:47 ` [PATCH RFC 4/6] net: rfkill: gpio: add device tree support Chen-Yu Tsai
[not found] ` <1389941251-32692-5-git-send-email-wens-jdAy2FN1RRM@public.gmane.org>
2014-01-17 16:47 ` Arnd Bergmann
[not found] ` <201401171747.46332.arnd-r2nGTMty4D4@public.gmane.org>
2014-01-17 17:43 ` Chen-Yu Tsai
[not found] ` <CAGb2v67UKiyfJbKZ_Frk3OwZupMPoA2Ck3Hj2zsRFXBQPztavg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-01-17 20:13 ` Arnd Bergmann
2014-01-17 23:11 ` Linus Walleij
[not found] ` <CACRpkdZOD4zeA8T5kbJ4c5NsnuzHCg1mw8rRMYNT9c4R-Qnc6A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-01-18 4:41 ` Chen-Yu Tsai
2014-01-20 8:10 ` Heikki Krogerus
2014-01-21 3:11 ` Alexandre Courbot [this message]
[not found] ` <CAAVeFuLP4MkfXGG1FMauvUw_J63zRXdhGwxqYy5W98L1wCQNbw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-01-21 9:35 ` Linus Walleij
[not found] ` <CACRpkdYiy+sya6NqRfAmsrFOXvaa3qX=qjRuTDW1vZVSaG1+Gg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-01-21 12:35 ` Arnd Bergmann
[not found] ` <201401211335.16885.arnd-r2nGTMty4D4@public.gmane.org>
2014-01-21 14:53 ` Alexandre Courbot
2014-01-21 15:25 ` Mika Westerberg
[not found] ` <CAAVeFuKFfAvSPYLmvWV5jjT-peZFJ8sJ2bbh4F=JAYoWLhjZpA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-01-21 18:50 ` Arnd Bergmann
2014-01-22 12:38 ` Mark Brown
2014-01-22 9:54 ` Linus Walleij
2014-01-22 9:58 ` Linus Walleij
[not found] ` <CACRpkdZbb=eO8YRtMn6hW0vn97PkHUo88e_o61DEC8=wPY3_PQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-01-22 11:00 ` Mika Westerberg
2014-01-27 14:24 ` Maxime Ripard
2014-01-29 4:01 ` Chen-Yu Tsai
2014-01-17 6:47 ` [PATCH RFC 5/6] net: rfkill: gpio: add clock-frequency device tree property Chen-Yu Tsai
2014-01-17 6:47 ` [PATCH RFC 6/6] ARM: sun7i: cubietruck: enable bluetooth module Chen-Yu Tsai
2014-01-17 20:26 ` [PATCH RFC 0/6] net: rfkill: gpio: Add device tree support Johannes Berg
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