linux-kernel - Re: [PATCH v4] leds: simatic-ipc-leds-gpio: make sure we have the GPIO providing driver

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Date:   Mon, 23 Jan 2023 21:48:59 +0100
From:   Henning Schild <henning.schild@...mens.com>
To:     Lee Jones <lee@...nel.org>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Pavel Machek <pavel@....cz>, linux-leds@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Andy Shevchenko <andy.shevchenko@...il.com>
Subject: Re: [PATCH v4] leds: simatic-ipc-leds-gpio: make sure we have the
 GPIO providing driver

Am Thu, 19 Jan 2023 21:02:40 +0000
schrieb Lee Jones <lee@...nel.org>:

> On Fri, 07 Oct 2022, Henning Schild wrote:
> 
> > If we register a "leds-gpio" platform device for GPIO pins that do
> > not exist we get a -EPROBE_DEFER and the probe will be tried again
> > later. If there is no driver to provide that pin we will poll
> > forever and also create a lot of log messages.
> > 
> > So check if that GPIO driver is configured, if so it will come up
> > eventually. If not, we exit our probe function early and do not even
> > bother registering the "leds-gpio". This method was chosen over
> > "Kconfig depends" since this way we can add support for more
> > devices and GPIO backends more easily without "depends":ing on all
> > GPIO backends.
> > 
> > Fixes: a6c80bec3c93 ("leds: simatic-ipc-leds-gpio: Add GPIO version
> > of Siemens driver") Reviewed-by: Andy Shevchenko
> > <andy.shevchenko@...il.com> Signed-off-by: Henning Schild
> > <henning.schild@...mens.com> ---
> >  drivers/leds/simple/simatic-ipc-leds-gpio.c | 2 ++
> >  1 file changed, 2 insertions(+)  
> 
> FYI: I'm going to try my best not to take another one like this.

understood!

> Please try to improve the whole situation for you next submission.

When i have to touch this again, which i will, i will propose either
"depend on all possible GPIO drivers" or introduce "#ifdef CONFIG"s.
Caring most about big configs as seen in distros like debian, even for
embedded systems ... i think i would prefer the first option, as it
will also be easier to maintain.

I do not see the whole infinite loop story on my plate, but if that got
fixed i would follow up taking the fix into account.

> Applied, thanks.

Thanks!

Henning

>