linux-kernel - Re: [PATCH RESEND v3 12/17] iio: adc: ad7768-1: Add GPIO controller support

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Message-ID: <7c5e2364-038b-48a8-ad67-3cf0f2fd2be3@baylibre.com>
Date: Thu, 20 Feb 2025 16:27:23 -0600
From: David Lechner <dlechner@...libre.com>
To: Linus Walleij <linus.walleij@...aro.org>,
 Jonathan Santos <Jonathan.Santos@...log.com>
Cc: linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, Sergiu Cuciurean
 <sergiu.cuciurean@...log.com>, lars@...afoo.de,
 Michael.Hennerich@...log.com, marcelo.schmitt@...log.com, jic23@...nel.org,
 robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
 jonath4nns@...il.com, marcelo.schmitt1@...il.com
Subject: Re: [PATCH RESEND v3 12/17] iio: adc: ad7768-1: Add GPIO controller
 support

On 2/19/25 2:34 PM, Linus Walleij wrote:
> Hi Jonathan/Sergiu,
> 
> thanks for your patch!
> 
> On Wed, Feb 12, 2025 at 7:20 PM Jonathan Santos
> <Jonathan.Santos@...log.com> wrote:
> 
>> From: Sergiu Cuciurean <sergiu.cuciurean@...log.com>
>>
>> The AD7768-1 has the ability to control other local hardware (such as gain
>> stages),to power down other blocks in the signal chain, or read local
>> status signals over the SPI interface.
>>
>> This change exports the AD7768-1's four gpios and makes them accessible
>> at an upper layer.
>>
>> Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@...log.com>
>> Co-developed-by: Jonathan Santos <Jonathan.Santos@...log.com>
>> Signed-off-by: Jonathan Santos <Jonathan.Santos@...log.com>
> 
> Is it not possible to use the gpio regmap library in this driver
> like we do in drivers/iio/addac/stx104.c?
> 
> It cuts down the code size of simple GPIO chips on random
> chips quite a lot.
> 
> Yours,
> Linus Walleij

I think the answer is "no" since we need to hold a conditional lock
while accessing registers. Namely: iio_device_claim_direct_mode()/
iio_device_release_direct_mode().

Unless we add some extra stuff to the gpio regmap implementation to
add optional callbacks to call these. Which could be worth it given
that quite a few ADCs provide GPIOs like this.