RE: [PATCH] i2c: tegra: Set ACPI node as primary fwnode

[Akhil R]

> On 18/11/2022 10:18, Thierry Reding wrote:
> > On Fri, Nov 18, 2022 at 09:38:52AM +0000, Jon Hunter wrote:
> >>
> >> On 17/11/2022 10:04, Akhil R wrote:
> >>> Set ACPI node as the primary fwnode of I2C adapter to allow
> >>> enumeration of child devices from the ACPI table
> >>>
> >>> Signed-off-by: Zubair Waheed <zwaheed@xxxxxxxxxx>
> >>> Signed-off-by: Akhil R <akhilrajeev@xxxxxxxxxx>
> >>> ---
> >>>    drivers/i2c/busses/i2c-tegra.c | 1 +
> >>>    1 file changed, 1 insertion(+)
> >>>
> >>> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> >>> index 954022c04cc4..69c9ae161bbe 100644
> >>> --- a/drivers/i2c/busses/i2c-tegra.c
> >>> +++ b/drivers/i2c/busses/i2c-tegra.c
> >>> @@ -1826,6 +1826,7 @@ static int tegra_i2c_probe(struct platform_device
> *pdev)
> >>>    	i2c_dev->adapter.class = I2C_CLASS_DEPRECATED;
> >>>    	i2c_dev->adapter.algo = &tegra_i2c_algo;
> >>>    	i2c_dev->adapter.nr = pdev->id;
> >>> +	ACPI_COMPANION_SET(&i2c_dev->adapter.dev,
> ACPI_COMPANION(&pdev->dev));
> >>>    	if (i2c_dev->hw->supports_bus_clear)
> >>>    		i2c_dev->adapter.bus_recovery_info =
> &tegra_i2c_recovery_info;
> >>
> >>
> >> Do we always want to set as the primary fwnode even when booting with
> >> device-tree? I some other drivers do, but I also see some others ...
> >>
> >>   if (has_acpi_companion(dev))
> >>          ACPI_COMPANION_SET(&i2c_dev->adapter.dev,
> >>                             ACPI_COMPANION(&pdev->dev));
> >>
> >> It would be nice to know why it is OK to always do this even for device-tree
> >> because it is not clear to me.
> >
> > ACPI_COMPANION() returns NULL if there is no ACPI companion, which will
> > cause ACPI_COMPANION_SET() to set the primary fwnode to NULL. If I read
> > the code for set_primary_fwnode() correctly, that's essentially a no-op
> > for DT devices.
> 
> Yes it does, but doesn't it is not clear to me if it is a good idea to
> pass NULL to set_primary_fwnode(). It does seem to handle this but my
> biggest gripe is the lack of explanation in the commit message why this
> is OK.
I saw ACPI_COMPANION_SET() as an empty function if CONFIG_ACPI is not set.
Yes, I agree that I should have mentioned this in the commit message.
Shall I send a v2 with the details added in the commit description? 

Regards,
Akhil