Re: [PATCH v3 6/6] platform/x86: dell-smo8800: Add support for probing for the accelerometer i2c address

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On Fri, Jun 21, 2024 at 2:26 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
>
> Unfortunately the SMOxxxx ACPI device does not contain the i2c-address
> of the accelerometer. So a DMI product-name to address mapping table
> is used.
>
> At support to have the kernel probe for the i2c-address for modesl

At --> Add ?

models

> which are not on the list.
>
> The new probing code sits behind a new probe_i2c_addr module parameter,
> which is disabled by default because probing might be dangerous.

...

> +/*
> + * This is the kernel version of the single register device sanity checks from
> + * the i2c_safety_check function from lm_sensors sensor-detect script:

i2c_safety_check()

> + * This is meant to prevent access to 1-register-only devices,
> + * which are designed to be accessed with SMBus receive byte and SMBus send
> + * byte transactions (i.e. short reads and short writes) and treat SMBus
> + * read byte as a real write followed by a read. The device detection
> + * routines would write random values to the chip with possibly very nasty
> + * results for the hardware. Note that this function won't catch all such
> + * chips, as it assumes that reads and writes relate to the same register,
> + * but that's the best we can do.
> + */

...

> +       err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, data ^ 0x01,

Is 0x01 defined already?
Or BIT(0) ?

> +                            I2C_SMBUS_BYTE_DATA, &smbus_data);
> +       if (err < 0)
> +               return err;
> +
> +       if (smbus_data.byte != (data ^ 0x01))

Ditto.

> +               return 0; /* Not a 1-register-only device. */

...

> +               dev_info(&device->dev, "Pass dell_smo8800.probe_i2c_addr=1 on the kernel commandline to probe, this may be dangerous!\n");

command line
...or...
cmdline

-- 
With Best Regards,
Andy Shevchenko





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