Re: [PATCH 6/6] gpio: macsmc: Add IRQ support

[Andy Shevchenko <andy.shevchenko@xxxxxxxxx>]

On Mon, Sep 5, 2022 at 4:04 PM Andy Shevchenko
<andy.shevchenko@xxxxxxxxx> wrote:
>
> On Mon, Sep 5, 2022 at 2:54 PM Russell King (Oracle)
> <linux@xxxxxxxxxxxxxxx> wrote:
> > On Thu, Sep 01, 2022 at 09:03:49PM +0300, Andy Shevchenko wrote:
> > > On Thu, Sep 1, 2022 at 5:18 PM Russell King <rmk+kernel@xxxxxxxxxxxxxxx> wrote:
>
> ...
>
> > > Usually we want to have handle_bad_irq() handler by default and in
> > > ->set_type() we lock a handler depending on the flags. Why is this not
> > > the case in this driver?
> >
> > "lock a handler" ? I guess you mean select a handler.
>
> Yes, I was a bit confused by API naming (irq_set_handler_locked() was it).
>
> > I don't see a reason why we couldn't switch between handle_bad_irq()
> > and handle_simple_irq(). I would guess (I don't know the implementation
> > details of the Apple platform) that the SMC forwards a message when the
> > IRQ happens, but I'm guessing that this is well tested on the platform
> > with the simple flow handler.
>
> I have had a real case where it makes quite a difference:
> eb441337c714 ("gpio: pca953x: Set IRQ type when handle Intel Galileo Gen 2")
>
> The missed ->irq_set_type() call shows a bug in the IRQ flow in the
> code. This became visible due to the switch to handle_bad_irq() and
> was hidden with other default handlers. After this I ask people to use
> the default handler to be a "bad" one.
>
> > Changing it to something else would need
> > discussion with the Asahi Linux folk.
>
>
>
> --
> With Best Regards,
> Andy Shevchenko



-- 
With Best Regards,
Andy Shevchenko