Re: [PATCH] i2c: sh_mobile: request IRQs after mapping registers

[Geert Uytterhoeven]

On Sat, 24 Oct 2026 at 00:09, Andi Shyti <andi.shyti@xxxxxxxxxx> wrote:
> On Sat, Oct 17, 2026 at 11:35:16PM -0400, Myeonghun Pak wrote:
> > The managed IRQ handlers are acquired before the managed register
> > mapping, so devres unmaps the registers before freeing the IRQs. A
> > transfer wakes its waiter before the ISR's final register read, and
> > unregistering the adapter does not synchronize these IRQs. An in-flight
> > handler can therefore still access the mapping when it is released
> > during driver detach.
> >
> > With forced-threaded IRQs, the handler can be preempted after waking the
> > transfer waiter and before its final ICSR read.
> >
> > Map the registers before requesting the IRQs so that managed cleanup
> > frees and synchronizes all handlers before unmapping their registers.
> > Keep IRQs available while unregistering the adapter because client
> > removal may perform transfers.
> >
> > This issue was identified as part of our ongoing research while
> > reviewing kernel code.
> >
> > Fixes: 7fe8a9993337 ("i2c: sh_mobile: devm conversion, irq setup")
>
> Normally, I don't like taking fixes that don't address real
> issues, especially speculative AI-generated fixes.
>
> However, this looks like a harmless reordering that seems
> correct, although the issue it addresses is rather
> hypothetical.
>
> I'll remove the Fixes: tag, since this is purely speculative,
> and apply the patch to i2c/i2c.

FWIW, no issues seen when boot-testing several platforms using
this driver.
Tested-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds