linux-kernel - Re: [PATCH 2/2] Input: exc3000 - Support power supply regulators

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Date:   Wed, 5 Jul 2023 14:49:21 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Mike Looijmans <mike.looijmans@...ic.nl>
Cc:     devicetree@...r.kernel.org, linux-input@...r.kernel.org,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] Input: exc3000 - Support power supply regulators

Hi Mike,

On Mon, Jul 03, 2023 at 10:45:36AM +0200, Mike Looijmans wrote:
> Add power supply regulator support to the exc3000 devices.
> 
> Signed-off-by: Mike Looijmans <mike.looijmans@...ic.nl>
> 
> ---
> 
>  drivers/input/touchscreen/exc3000.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/input/touchscreen/exc3000.c b/drivers/input/touchscreen/exc3000.c
> index 4af4c1e5d0da..3e50af8a4a2d 100644
> --- a/drivers/input/touchscreen/exc3000.c
> +++ b/drivers/input/touchscreen/exc3000.c
> @@ -18,6 +18,7 @@
>  #include <linux/interrupt.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
> +#include <linux/regulator/consumer.h>
>  #include <linux/sizes.h>
>  #include <linux/timer.h>
>  #include <asm/unaligned.h>
> @@ -360,6 +361,12 @@ static int exc3000_probe(struct i2c_client *client)
>  	if (IS_ERR(data->reset))
>  		return PTR_ERR(data->reset);
>  
> +	/* For proper reset sequence, enable power while reset asserted */
> +	error = devm_regulator_get_enable_optional(&client->dev, "vdd");
> +	if (error && error != -ENODEV)
> +		dev_err_probe(&client->dev, error,
> +			      "failed to request vdd regulator\n");


If there is a regulator described in the firmware we should not continue
with initializing the device if we fail to grab/enable it. Think about
what happens if you get -EPROBE_DEFER here. You should return here.

Also, why are you using the _optional() variant? VDD is not an optional
for the controller. regulator_get_optional() is needed when you need to
alter the behavior of the device/driver depending on the presence of an
optional supply, whereas here it should work fine with a sub supply that
will be created if you simply call devm_regulator_get_enable() and there
is not regulator mentioned in DT/ACPI for the board.

Thanks.

-- 
Dmitry