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

[Frank Li]

On Sat, Dec 14, 2024 at 12:02:56AM +0100, Uwe Kleine-König wrote:
> Hello Frank,
>
> On Fri, Dec 13, 2024 at 05:23:09PM -0500, Frank Li wrote:
> > From: Luwei Zhou <b45643@xxxxxxxxxxxxx>
> >
> > 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@xxxxxxxxxxxxx>
> > Signed-off-by: Fugang Duan <B38611@xxxxxxxxxxxxx>
> > Signed-off-by: Vipul Kumar <vipul_kumar@xxxxxxxxxx>
> > Signed-off-by: Dong Aisheng <aisheng.dong@xxxxxxx>
> > Signed-off-by: Frank Li <Frank.Li@xxxxxxx>
> > ---
> >  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.

yes, it should be better

	if (!i2c_check_functionality())
		....

i2c_check_functionality() return 1 if adapter supports everything we need.

Frank

>
> > +	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