linux-kernel - Re: [PATCH 1/1] input: mma8450: Add chip ID check in probe

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Message-ID: <bzzzezoon5u5pufpbkn3fnm2dtbrzatx4w4tbdstcdmowvfzzn@cplbmxtgmu6z>
Date: Sat, 14 Dec 2024 00:02:56 +0100
From: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To: Frank Li <Frank.Li@....com>
Cc: Dmitry Torokhov <dmitry.torokhov@...il.com>, 
	Luwei Zhou <b45643@...escale.com>, Vipul Kumar <vipul_kumar@...tor.com>, 
	Dong Aisheng <aisheng.dong@....com>, 
	"open list:INPUT (KEYBOARD, MOUSE, JOYSTICK, TOUCHSCREEN)..." <linux-input@...r.kernel.org>, open list <linux-kernel@...r.kernel.org>, imx@...ts.linux.dev
Subject: Re: [PATCH 1/1] input: mma8450: Add chip ID check in probe

Hello Frank,

On Fri, Dec 13, 2024 at 05:23:09PM -0500, Frank Li wrote:
> From: Luwei Zhou <b45643@...escale.com>
> 
> Prevent continuous polling error logs by adding a chip ID check in the
> probe  function. This ensures the driver only proceeds when the mma8450 is
> present, avoiding issues in scenarios like missing add-on cards.
> 
> Signed-off-by: Luwei Zhou <b45643@...escale.com>
> Signed-off-by: Fugang Duan <B38611@...escale.com>
> Signed-off-by: Vipul Kumar <vipul_kumar@...tor.com>
> Signed-off-by: Dong Aisheng <aisheng.dong@....com>
> Signed-off-by: Frank Li <Frank.Li@....com>
> ---
>  drivers/input/misc/mma8450.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/input/misc/mma8450.c b/drivers/input/misc/mma8450.c
> index 08412239b8e69..da941748ed29b 100644
> --- a/drivers/input/misc/mma8450.c
> +++ b/drivers/input/misc/mma8450.c
> @@ -38,6 +38,8 @@
>  
>  #define MMA8450_CTRL_REG1	0x38
>  #define MMA8450_CTRL_REG2	0x39
> +#define MMA8450_ID		0xc6
> +#define MMA8450_WHO_AM_I	0x0f
>  
>  static int mma8450_read(struct i2c_client *c, unsigned int off)
>  {
> @@ -148,8 +150,20 @@ static void mma8450_close(struct input_dev *input)
>   */
>  static int mma8450_probe(struct i2c_client *c)
>  {
> +	struct i2c_adapter *adapter = to_i2c_adapter(c->dev.parent);

+	struct i2c_adapter *adapter = c->adapter;

>  	struct input_dev *input;
> -	int err;
> +	int err, client_id;
> +
> +	err = i2c_check_functionality(adapter,
> +				      I2C_FUNC_SMBUS_BYTE | I2C_FUNC_SMBUS_BYTE_DATA);
> +	if (!err)
> +		return err;

How unusual. I would have expected no ! here.

> +	client_id = i2c_smbus_read_byte_data(c, MMA8450_WHO_AM_I);
> +	if (client_id != MMA8450_ID)
> +		return dev_err_probe(&c->dev, -EINVAL,
> +				     "read chip ID 0x%x is not equal to 0x%x!\n",
> +				     client_id, MMA8450_ID);

Given that here you emit an error message, maybe add an error message
above, too?

>  	input = devm_input_allocate_device(&c->dev);
>  	if (!input)

Best regards
Uwe

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