Re: [PATCH v3 2/2] i2c: Add GPIO-based hotplug gate

Michał Mirosław
2023-07-30T21:56:12Z

On Sun, Jul 30, 2023 at 10:30:56PM +0200, Krzysztof Kozlowski wrote:
> On 29/07/2023 18:08, Svyatoslav Ryhel wrote:
> > From: Michał Mirosław <mirq-linux@rere.qmqm.pl>
> >
> > Implement driver for hot-plugged I2C busses, where some devices on
> > a bus are hot-pluggable and their presence is indicated by GPIO line.
[...]
> > + priv->irq = platform_get_irq(pdev, 0);
> > + if (priv->irq < 0)
> > + return dev_err_probe(&pdev->dev, priv->irq,
> > + "failed to get IRQ %d\n", priv->irq);
> > +
> > + ret = devm_request_threaded_irq(&pdev->dev, priv->irq, NULL,
> > + i2c_hotplug_interrupt,
> > + IRQF_ONESHOT | IRQF_SHARED,
>
> Shared IRQ with devm is a recipe for disaster. Are you sure this is a
> shared one? You have a remove() function which also points that it is
> not safe. You can:
> 1. investigate to be sure it is 100% safe (please document why do you
> think it is safe)

Could you elaborate on what is unsafe in using devm with shared
interrupts (as compared to non-shared or not devm-managed)?

The remove function is indeed reversing the order of cleanup. The
shutdown path can be fixed by removing `remove()` and adding
`devm_add_action_or_reset(...deactivate)` before the IRQ is registered.

Best Regards
Michał Mirosław