Re: [RFC PATCH 1/4] i2c: allow drivers to announce that they are IRQ safe

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On Tue, Aug 14, 2018 at 12:16 AM, Stefan Lengfeld
<contact@xxxxxxxxxxxxxxx> wrote:
> Like the PM subsystem routine pm_runtime_irq_safe() and flag 'irq_safe'

No, it seems unlike as in PM. PM has one crucial detail which is done
together with enabling IRQ safety.

> add a similar function i2c_adapter_irq_safe() to the I2C core. A driver
> should be able to announce whether his transfer implementations are safe
> to be called in IRQ disabled or atomic contexts, also called polling
> mode or sleep free operation.
>
> Making I2C transfers in atomic context is sometimes needed, e.g.  for
> reboot handlers.
>
> Every driver should be able to declare explicitly whether IRQ disabled
> operation is supported or not. When you try make a I2C transfer in
> atomic contexts, it's already hard enough to ensure that every code path
> through the kernel is sleep-free. So give the curious developer a strong
> hint whether a driver supports atomic operation or not. Fail early
> instead of hoping that the LOCKDEP framework noticed the programming
> error.

-- 
With Best Regards,
Andy Shevchenko



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