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

["Pali Rohár" <pali@kernel.org>]

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.

> Regards,
> 
> Hans
> 
> 
> 
> 	
> 
> > And if really not, what about
> > sharing (or exporting) list from the i801 driver?
> > 
> > I'm just worried that this PCI id list will increase in the future and
> > it would be required to add a new and new id into it...
> > 
> >> +	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;
> >> +}
> > 
>