Re: [PATCH 3/6] platform/x86: dell-smo8800: Move instantiation of lis3lv02d i2c_client from i2c-i801 to dell-smo8800

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 1/5/24 19:26, Pali Rohár wrote:
> On Friday 05 January 2024 17:31:32 Hans de Goede wrote:
>> Hi Pali,
>>
>> On 12/24/23 22:55, Pali Rohár wrote:
>>> On Sunday 24 December 2023 22:36:19 Hans de Goede wrote:
>>>> +static int smo8800_find_i801(struct device *dev, void *data)
>>>> +{
>>>> +	static const u16 i801_idf_pci_device_ids[] = {
>>>> +		0x1d70, /* Patsburg (PCH) */
>>>> +		0x1d71, /* Patsburg (PCH) */
>>>> +		0x1d72, /* Patsburg (PCH) */
>>>> +		0x8d7d, /* Wellsburg (PCH) */
>>>> +		0x8d7e, /* Wellsburg (PCH) */
>>>> +		0x8d7f, /* Wellsburg (PCH) */
>>>> +	};
>>>
>>> I'm not happy with seeing another hardcoded list of device ids in the
>>> driver. Are not we able to find compatible i801 adapter without need to
>>> hardcode this list there in smo driver?
>>
>> I agree that having this hardcoded is not ideal.
>>
>> The problem is that for a couple of generations (Patsburg is for
>> Sandy Bridge and Ivybridge and Wellsburg is for Haswell and Broadwell)
>> intel had multiple i2c-i801 controllers / I2C-busses in the PCH
>> and the i2c_client needs to be instantiated on the primary
>> i2c-i801 (compatible) controller.
>>
>> Luckily Intel has only done this for these 2 generations PCH
>> all older and newer PCHs only have 1 i2c-i801 I2C bus.
>>
>> So even though having this hardcoded is not ideal,
>> the list should never change since it is only for
>> this 2 somewhat old PCH generations and new generations
>> are not impacted. So I believe that this is the best
>> solution.
> 
> I see. Seems that this is the best solution which we have.
> 
> Anyway, is not possible to use pci_dev_driver() to find i801 driver and
> from it takes that list of devices which have FEATURE_IDF flag? I have
> looked at the code only quickly and maybe it could be possible. Just an
> idea.

That is an interesting idea, but ...

that would mean interpreting the driver_data set by the i2c-i801
driver inside the dell-smo8800 code, so this would basically rely on
the meaning of that driver_data never changing. I would rather just
duplicate the 6 PCI ids and decouple the 2 drivers.

Regards,

Hans




>>>> +	struct i2c_adapter *adap, **adap_ret = data;
>>>> +	struct pci_dev *pdev;
>>>> +	int i;
>>>> +
>>>> +	adap = i2c_verify_adapter(dev);
>>>> +	if (!adap)
>>>> +		return 0;
>>>> +
>>>> +	if (!strstarts(adap->name, "SMBus I801 adapter"))
>>>> +		return 0;
>>>> +
>>>> +	/* The parent of an I801 adapter is always a PCI device */
>>>> +	pdev = to_pci_dev(adap->dev.parent);
>>>> +	for (i = 0; i < ARRAY_SIZE(i801_idf_pci_device_ids); i++) {
>>>> +		if (pdev->device == i801_idf_pci_device_ids[i])
>>>> +			return 0; /* Only register client on main SMBus channel */
>>>> +	}
>>>> +
>>>> +	*adap_ret = i2c_get_adapter(adap->nr);
>>>> +	return 1;
>>>> +}
>>>
>>
>