[PATCH v2 01/12] i2c: allow setting the parent device and OF node through the adapter struct

[Andreas Kemnade]

On Mon, 2 Mar 2026 03:08:24 -0800
Bartosz Golaszewski <brgl at kernel.org> wrote:

> On Mon, 2 Mar 2026 11:38:27 +0100, Kalle Niemi <kaleposti at gmail.com> said:
> > On 3/2/26 10:55, Bartosz Golaszewski wrote:  
> >> On Mon, Mar 2, 2026 at 8:47 AM Kalle Niemi <kaleposti at gmail.com> wrote:  
> >>> On 2/23/26 11:05, Bartosz Golaszewski wrote:  
> >>>> In order to stop i2c bus drivers from dereferencing the struct device
> >>>> embedded in struct i2c_adapter, let's allow configuring the parent
> >>>> device and OF-node of the adapter directly through dedicated fields.
> >>>> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski at oss.qualcomm.com>
> >>>> ---  
> >>> Hello,
> >>> Automated driver test system bisected this commit to be the first bad
> >>> commit, linux-next next-20260227 was tested. Failed tests include driver
> >>> tests for ROHM PMIC and accelerometers, which are connected to
> >>> BeagleBone Black.
> >>> The failed driver tests all fail to first i2cget and the tests stop
> >>> there: "Could not open file '/dev/i2c-2' or 'dev/i2c/2': No such file or
> >>> directory".  
> >> Wolfram: well, now it would actually be useful to know which commit
> >> exactly is the culprit so maybe splitting the changes is not a bad
> >> idea after all.
> >> Kalle: which i2c bus driver fails here? Any errors in kernel log?
> >> Bart  
> >
> > Hello Bart,
> >
> > i2c-1 and i2c-2 are failing. I am not seeing any i2c errors in kernel log. I got two failures without the dmesg available (this is bugged test sequence, and not a kernel crash), but those got the same stdout message "Could not open file ...." as all others.
> >
> > -Kalle
> >  
> 
> I meant what driver are you using but I suppose it's i2c-omap.
> 
> Can you try the following change and let me know if it fixes the issue?
> 
> diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
> index dd8cec9b04c6..01656f82d2c6 100644
> --- a/drivers/i2c/i2c-core-base.c
> +++ b/drivers/i2c/i2c-core-base.c
> @@ -1548,6 +1548,11 @@ static int i2c_register_adapter(struct i2c_adapter *adap)
>  	if (adap->timeout == 0)
>  		adap->timeout = HZ;
> 
> +	if (!adap->dev.parent)
> +		adap->dev.parent = adap->parent;
> +	if (!adap->dev.of_node)
> +		adap->dev.of_node = adap->of_node;
> +
>  	/* register soft irqs for Host Notify */
>  	res = i2c_setup_host_notify_irq_domain(adap);
>  	if (res) {
> @@ -1561,11 +1566,6 @@ static int i2c_register_adapter(struct i2c_adapter *adap)
>  	adap->dev.type = &i2c_adapter_type;
>  	device_initialize(&adap->dev);
> 
> -	if (!adap->dev.parent)
> -		adap->dev.parent = adap->parent;
> -	if (!adap->dev.of_node)
> -		adap->dev.of_node = adap->of_node;
> -
>  	/*
>  	 * This adapter can be used as a parent immediately after device_add(),
>  	 * setup runtime-pm (especially ignore-children) before hand.
> 
No changes here. Devices probe, bus indexes are still shifted.
If I take that into account, i2cget still works.

But I think there is no defined order anyways. So if
I would add e.g. usb device provoding i2c busses early than
omap-i2c for some odd reason, things were messed anyways.

On the other hand, just having numbers skipped seems to be odd.

Regards,
Andreas