linux-kernel - Re: [PATCHv2 3/5] net: rfkill: gpio: remove gpio names

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Message-ID: <5319497F.9080003@wwwdotorg.org>
Date:	Thu, 06 Mar 2014 21:22:23 -0700
From:	Stephen Warren <swarren@...dotorg.org>
To:	Chen-Yu Tsai <wens@...e.org>,
	Linus Walleij <linus.walleij@...aro.org>
CC:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Johannes Berg <johannes@...solutions.net>,
	"David S. Miller" <davem@...emloft.net>,
	Rhyland Klein <rklein@...dia.com>,
	Marc Dietrich <marvin24@....de>, Arnd Bergmann <arnd@...db.de>,
	Alexandre Courbot <gnurou@...il.com>,
	linux-wireless <linux-wireless@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCHv2 3/5] net: rfkill: gpio: remove gpio names

On 03/06/2014 08:43 PM, Chen-Yu Tsai wrote:
> On Fri, Mar 7, 2014 at 11:41 AM, Linus Walleij <linus.walleij@...aro.org> wrote:
>> On Wed, Mar 5, 2014 at 10:59 AM, Stephen Warren <swarren@...dotorg.org> wrote:
>>> On 03/04/2014 07:37 PM, Linus Walleij wrote:
>>>> On Wed, Mar 5, 2014 at 10:18 AM, Stephen Warren <swarren@...dotorg.org> wrote:
>>>>> On 03/04/2014 06:43 PM, Linus Walleij wrote:
>>>>
>>>>>> If I understand the situation correctly it's like ACPI does not have named
>>>>>> GPIOs so keeping specifying this in DT GPIO bindings is counter-productive
>>>>>> to the work of abstracting the access to GPIO handlers so that drivers
>>>>>> need not know whether ACPI or DT is used for describing the hardware.
>>>>>
>>>>> For devices that already have both ACPI and DT bindings, we can't
>>>>> pretend they can be the same; they are already potentially different. We
>>>>> simply need to parse DT and ACPI differently, since that's the sway
>>>>> their bindings are defined.
>>>>>
>>>>> For any devices that don't have both ACPI and DT bindings, I agree we
>>>>> should certainly strive to make any new bindings aligned so we don't
>>>>> have to deal with this for them.
>>>>>
>>>>> However, we can't change the past.
>>>>
>>>> Yeah, right, so for this very driver there are no bindings defined (yet)
>>>> and the only device tree I can find referencing it is the Tegra20-paz00
>>>> and it just use gpios = <>;
>>>>
>>>> So in this case I think this patch is the right way forward, but I admit
>>>> I'm really uncertain in the general case.
>>>
>>> If there are no bindings defined at all yet, then we can define both DT
>>> and ACPI bindings to use name-based GPIOs. Index-based lookups aren't a
>>> good way forward.
>>
>> After Mark clarifying that ACPI is going to have named GPIOs I'm
>> totally aligned on this, so OK!
> 
> Glad to hear this, but is it possible to get rid of the index in current
> drivers? Or change the behavior to name-based OR index-based lookups.
> This might break any DTs that have multiple GPIOs defined under one
> property though.

For any bindings that are already defined to use index-based lookups, I
think we have to continue using them, for backwards-compatibility with
old DTs (and I assume old ACPI databases need the same thing).

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