linux-kernel - Re: [PATCH v4 07/10] Input: wacom_i2c

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Date:   Mon, 29 Mar 2021 13:33:38 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Alistair Francis <alistair@...stair23.me>
Cc:     linux-input@...r.kernel.org, linux-imx@....com,
        kernel@...gutronix.de, linux-kernel@...r.kernel.org,
        alistair23@...il.com, Alistair Francis <alistair@...stair22.me>
Subject: Re: [PATCH v4 07/10] Input: wacom_i2c - Add support for reset control

Hi Alistair,

On Thu, Mar 25, 2021 at 09:52:27PM -0400, Alistair Francis wrote:
> From: Alistair Francis <alistair@...stair22.me>
> 
> Signed-off-by: Alistair Francis <alistair@...stair22.me>
> ---
> v4:
>  - Initial commit
> 
>  drivers/input/touchscreen/wacom_i2c.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/input/touchscreen/wacom_i2c.c b/drivers/input/touchscreen/wacom_i2c.c
> index 84c7ccb737bd..28004b1180c9 100644
> --- a/drivers/input/touchscreen/wacom_i2c.c
> +++ b/drivers/input/touchscreen/wacom_i2c.c
> @@ -55,6 +55,7 @@ struct wacom_features {
>  struct wacom_i2c {
>  	struct i2c_client *client;
>  	struct input_dev *input;
> +	struct reset_control *rstc;
>  	struct touchscreen_properties props;
>  	u8 data[WACOM_QUERY_SIZE];
>  	bool prox;
> @@ -175,6 +176,8 @@ static int wacom_i2c_open(struct input_dev *dev)
>  	struct wacom_i2c *wac_i2c = input_get_drvdata(dev);
>  	struct i2c_client *client = wac_i2c->client;
>  
> +	reset_control_reset(wac_i2c->rstc);

Why does this device need to be reset on every open compared to doing it
in probe?

> +
>  	enable_irq(client->irq);
>  
>  	return 0;
> @@ -193,6 +196,7 @@ static int wacom_i2c_probe(struct i2c_client *client,
>  {
>  	struct wacom_i2c *wac_i2c;
>  	struct input_dev *input;
> +	struct reset_control *rstc;
>  	struct wacom_features features = { 0 };
>  	int error;
>  
> @@ -201,6 +205,12 @@ static int wacom_i2c_probe(struct i2c_client *client,
>  		return -EIO;
>  	}
>  
> +	rstc = devm_reset_control_get_optional_exclusive(&client->dev, NULL);
> +	if (IS_ERR(rstc)) {
> +		dev_err(&client->dev, "Failed to get reset control before init\n");
> +		return PTR_ERR(rstc);
> +	}

I think majority users will have this controller reset line connected to
a GPIO. I briefly looked into reset controller code and I do not see it
supporting this case. How is this device connected on your board?

> +
>  	error = wacom_query_device(client, &features);
>  	if (error)
>  		return error;
> @@ -214,6 +224,7 @@ static int wacom_i2c_probe(struct i2c_client *client,
>  
>  	wac_i2c->client = client;
>  	wac_i2c->input = input;
> +	wac_i2c->rstc = rstc;
>  
>  	input->name = "Wacom I2C Digitizer";
>  	input->id.bustype = BUS_I2C;
> -- 
> 2.31.0
> 

Thanks.

-- 
Dmitry