linux-kernel - Re: [PATCH RFC 0/9] gpio: improve support for shared GPIOs

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Message-ID: <6fe16d18-b2e3-4a33-b03a-a30561dabbbf@kernel.org>
Date: Mon, 6 Oct 2025 22:52:06 +0100
From: Srinivas Kandagatla <srini@...nel.org>
To: Bartosz Golaszewski <brgl@...ev.pl>,
 Manivannan Sadhasivam <mani@...nel.org>
Cc: Dmitry Torokhov <dmitry.torokhov@...il.com>, Kees Cook <kees@...nel.org>,
 Mika Westerberg <westeri@...nel.org>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Linus Walleij <linus.walleij@...aro.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Saravana Kannan <saravanak@...gle.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Andy Shevchenko <andy@...nel.org>, Catalin Marinas
 <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 Srinivas Kandagatla <srini@...nel.org>, Liam Girdwood <lgirdwood@...il.com>,
 Mark Brown <broonie@...nel.org>, Jaroslav Kysela <perex@...ex.cz>,
 Takashi Iwai <tiwai@...e.com>, linux-hardening@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-sound@...r.kernel.org,
 linux-arm-msm@...r.kernel.org,
 Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH RFC 0/9] gpio: improve support for shared GPIOs



On 10/6/25 5:10 PM, Bartosz Golaszewski wrote:
> On Mon, Oct 6, 2025 at 5:43 PM Manivannan Sadhasivam <mani@...nel.org> wrote:
>>
>> On Wed, Sep 24, 2025 at 11:25:12AM -0700, Dmitry Torokhov wrote:
>>> Hi Bartosz,
>>>
>>>>
>>>> The practical use-case for this are the powerdown GPIOs shared by
>>>> speakers on Qualcomm db845c platform, however I have also extensively
>>>> tested it using gpio-virtuser on arm64 qemu with various DT
>>>> configurations.
>>>
>>> How is this different from the existing gpio-backed regulator/supply?
>>> IMO GPIOs are naturally exclusive-use resources (in cases when you need
>>> to control them, not simply read their state), and when there is a need
>>> to share them there are more appropriate abstractions that are built on
>>> top of GPIOs...
>>>
>>
>> Not always... For something like shared reset line, consumers request the line
>> as GPIO and expect gpiolib to do resource manangement.
>>
> 
> They could use the reset API and it would implicitly create a virtual
> device that requests the reset GPIO and controls its enable count.
> Except that some devices also do a specific reset sequence with delays
> etc. That would require some additional logic in reset-gpio.
That should be a platform specific reset controller driver.

> 
> Bart