Re: [PATCH v2 2/3] pwm: tegra: Check for match_data being NULL

[Uwe Kleine-König]

Hello Thierry,

On Mon, Sep 21, 2026 at 11:47:17AM +0200, Thierry Reding wrote:
> On Fri, Sep 18, 2026 at 04:33:46PM +0200, Uwe Kleine-König wrote:
> > It's unlikely but not impossible that of_device_get_match_data() returns
> > NULL. Handle this case instead of triggering a NULL pointer exception.
> > 
> > Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxx>
> > ---
> >  drivers/pwm/pwm-tegra.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> > 
> > diff --git a/drivers/pwm/pwm-tegra.c b/drivers/pwm/pwm-tegra.c
> > index efb7ab60f602..b461d3877f43 100644
> > --- a/drivers/pwm/pwm-tegra.c
> > +++ b/drivers/pwm/pwm-tegra.c
> > @@ -323,6 +323,14 @@ static int tegra_pwm_probe(struct platform_device *pdev)
> >  	int ret;
> >  
> >  	soc = of_device_get_match_data(dev);
> > +	if (!soc) {
> > +		/*
> > +		 * This can only happen if pdev was matched via pdev->name
> > +		 * (which should not happen today) or in combination with a
> > +		 * driver override.
> > +		 */
> > +		return dev_err_probe(dev, -ENODEV, "Unsupported device\n");
> > +	}
> 
> We don't usually do this. Matching via anything other than OF device ID
> tables (or ACPI, I suppose) is a programming error and you deserve the
> crash which forces you to fix things rather than continue with an error
> that is easy to miss.

I don't agree to "you deserve the crash". IMHO even root should be
unable to make the kernel crash. I don't understand what you think
should be fixed if I hit that crash. My userspace interactions in /sys?
Which error is easy to miss?

> Driver overrides aren't going to work with these devices anyway, so I'm
> beginning to think it might be worth looking into opting out of the
> override behaviour for select drivers.

I think there are much more drivers that don't expect to be forced on a
device, so opting in for override would be a more sensible result. Of
course the path to there is more painful ...

Best regards
Uwe

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