[PATCH v2] gpio: mockup: Allow probing from device tree

[PATCH v2] gpio: mockup: Allow probing from device tree

[Vincent Whitchurch]

Allow the mockup driver to be probed via the device tree without any
module parameters, allowing it to be used to configure and test higher
level drivers like the leds-gpio driver and corresponding userspace
before actual hardware is available.

Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
---
v2: Remove most of the added code, since the latest driver doesn't need it.
    Drop DT binding document, since Rob Herring was OK with not documenting
    this:
    https://lore.kernel.org/linux-devicetree/5baa1ae6.1c69fb81.847f2.3ab1@mx.google.com/

 drivers/gpio/gpio-mockup.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/gpio/gpio-mockup.c b/drivers/gpio/gpio-mockup.c
index 67ed4f238d43..c93892a6936a 100644
--- a/drivers/gpio/gpio-mockup.c
+++ b/drivers/gpio/gpio-mockup.c
@@ -13,6 +13,7 @@
 #include <linux/gpio/driver.h>
 #include <linux/interrupt.h>
 #include <linux/irq.h>
+#include <linux/of.h>
 #include <linux/irq_sim.h>
 #include <linux/irqdomain.h>
 #include <linux/module.h>
@@ -460,9 +461,18 @@ static int gpio_mockup_probe(struct platform_device *pdev)
 	return 0;
 }
 
+#ifdef CONFIG_OF
+static const struct of_device_id gpio_mockup_of_match[] = {
+	{ .compatible = "gpio-mockup", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, gpio_mockup_of_match);
+#endif
+
 static struct platform_driver gpio_mockup_driver = {
 	.driver = {
 		.name = "gpio-mockup",
+		.of_match_table = of_match_ptr(gpio_mockup_of_match),
 	},
 	.probe = gpio_mockup_probe,
 };
@@ -556,8 +566,7 @@ static int __init gpio_mockup_init(void)
 {
 	int i, num_chips, err;
 
-	if ((gpio_mockup_num_ranges < 2) ||
-	    (gpio_mockup_num_ranges % 2) ||
+	if ((gpio_mockup_num_ranges % 2) ||
 	    (gpio_mockup_num_ranges > GPIO_MOCKUP_MAX_RANGES))
 		return -EINVAL;
 
-- 
2.28.0

Re: [PATCH v2] gpio: mockup: Allow probing from device tree

[Bartosz Golaszewski]

On Tue, Oct 27, 2020 at 2:54 PM Vincent Whitchurch
<vincent.whitchurch@axis.com> wrote:
>
> Allow the mockup driver to be probed via the device tree without any
> module parameters, allowing it to be used to configure and test higher
> level drivers like the leds-gpio driver and corresponding userspace
> before actual hardware is available.
>
> Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
> ---
> v2: Remove most of the added code, since the latest driver doesn't need it.
>     Drop DT binding document, since Rob Herring was OK with not documenting
>     this:
>     https://lore.kernel.org/linux-devicetree/5baa1ae6.1c69fb81.847f2.3ab1@mx.google.com/
>
>  drivers/gpio/gpio-mockup.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpio/gpio-mockup.c b/drivers/gpio/gpio-mockup.c
> index 67ed4f238d43..c93892a6936a 100644
> --- a/drivers/gpio/gpio-mockup.c
> +++ b/drivers/gpio/gpio-mockup.c
> @@ -13,6 +13,7 @@
>  #include <linux/gpio/driver.h>
>  #include <linux/interrupt.h>
>  #include <linux/irq.h>
> +#include <linux/of.h>

Please keep the includes ordered alphabetically.

>  #include <linux/irq_sim.h>
>  #include <linux/irqdomain.h>
>  #include <linux/module.h>
> @@ -460,9 +461,18 @@ static int gpio_mockup_probe(struct platform_device *pdev)
>         return 0;
>  }
>
> +#ifdef CONFIG_OF
> +static const struct of_device_id gpio_mockup_of_match[] = {
> +       { .compatible = "gpio-mockup", },
> +       {},
> +};
> +MODULE_DEVICE_TABLE(of, gpio_mockup_of_match);
> +#endif

You don't need this ifdef - of_match_ptr() will evaluate to NULL if
CONFIG_OF is disabled and the compiler will optimize this struct out.

Bartosz

> +
>  static struct platform_driver gpio_mockup_driver = {
>         .driver = {
>                 .name = "gpio-mockup",
> +               .of_match_table = of_match_ptr(gpio_mockup_of_match),
>         },
>         .probe = gpio_mockup_probe,
>  };
> @@ -556,8 +566,7 @@ static int __init gpio_mockup_init(void)
>  {
>         int i, num_chips, err;
>
> -       if ((gpio_mockup_num_ranges < 2) ||
> -           (gpio_mockup_num_ranges % 2) ||
> +       if ((gpio_mockup_num_ranges % 2) ||
>             (gpio_mockup_num_ranges > GPIO_MOCKUP_MAX_RANGES))
>                 return -EINVAL;
>
> --
> 2.28.0
>

Re: [PATCH v2] gpio: mockup: Allow probing from device tree

[Vincent Whitchurch]

On Tue, Oct 27, 2020 at 07:12:13PM +0100, Bartosz Golaszewski wrote:
> On Tue, Oct 27, 2020 at 2:54 PM Vincent Whitchurch
> <vincent.whitchurch@axis.com> wrote:
> > diff --git a/drivers/gpio/gpio-mockup.c b/drivers/gpio/gpio-mockup.c
> > index 67ed4f238d43..c93892a6936a 100644
> > --- a/drivers/gpio/gpio-mockup.c
> > +++ b/drivers/gpio/gpio-mockup.c
> > @@ -13,6 +13,7 @@
> >  #include <linux/gpio/driver.h>
> >  #include <linux/interrupt.h>
> >  #include <linux/irq.h>
> > +#include <linux/of.h>
> 
> Please keep the includes ordered alphabetically.

Thanks, fixed in v3.

> >  #include <linux/irq_sim.h>
> >  #include <linux/irqdomain.h>
> >  #include <linux/module.h>
> > @@ -460,9 +461,18 @@ static int gpio_mockup_probe(struct platform_device *pdev)
> >         return 0;
> >  }
> >
> > +#ifdef CONFIG_OF
> > +static const struct of_device_id gpio_mockup_of_match[] = {
> > +       { .compatible = "gpio-mockup", },
> > +       {},
> > +};
> > +MODULE_DEVICE_TABLE(of, gpio_mockup_of_match);
> > +#endif
> 
> You don't need this ifdef - of_match_ptr() will evaluate to NULL if
> CONFIG_OF is disabled and the compiler will optimize this struct out.

The compiler can't optimise out the struct in the case of a module build
since there is a reference from the MODULE_DEVICE_TABLE:

 $ grep CONFIG_OF .config
 # CONFIG_OF is not set
 $ nm drivers/gpio/gpio-mockup.ko  | grep of_
 00000000 r gpio_mockup_of_match
 00000000 R __mod_of__gpio_mockup_of_match_device_table

But these few wasted bytes don't matter so I removed the CONFIG_OF
anyway as you suggested.

Re: [PATCH v2] gpio: mockup: Allow probing from device tree

[Andy Shevchenko]

On Wed, Oct 28, 2020 at 8:41 PM Bartosz Golaszewski <brgl@bgdev.pl> wrote:
> On Tue, Oct 27, 2020 at 2:54 PM Vincent Whitchurch
> <vincent.whitchurch@axis.com> wrote:

...

> > +#include <linux/of.h>
>
> Please keep the includes ordered alphabetically.

Besides the fact that that is a wrong header to be included.
mod_devicetable.h is the correct one.
(See also below)

...

> > +#ifdef CONFIG_OF
> > +static const struct of_device_id gpio_mockup_of_match[] = {
> > +       { .compatible = "gpio-mockup", },
> > +       {},
> > +};
> > +MODULE_DEVICE_TABLE(of, gpio_mockup_of_match);
> > +#endif
>
> You don't need this ifdef - of_match_ptr() will evaluate to NULL if
> CONFIG_OF is disabled and the compiler will optimize this struct out.

It's not so. If you drop ugly ifdeffery (and I vote for that, see also
above) the of_match_ptr() must be dropped as well.
Otherwise the compiler will issue the warning. So it is either all or none.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2] gpio: mockup: Allow probing from device tree

[Andy Shevchenko]

On Wed, Oct 28, 2020 at 10:25 PM Andy Shevchenko
<andy.shevchenko@gmail.com> wrote:
> On Wed, Oct 28, 2020 at 8:41 PM Bartosz Golaszewski <brgl@bgdev.pl> wrote:

...

> It's not so. If you drop ugly ifdeffery (and I vote for that, see also

It's not so -> It's not so simple.

> above) the of_match_ptr() must be dropped as well.
> Otherwise the compiler will issue the warning. So it is either all or none.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2] gpio: mockup: Allow probing from device tree

[Vincent Whitchurch]

On Wed, Oct 28, 2020 at 09:25:32PM +0100, Andy Shevchenko wrote:
> On Wed, Oct 28, 2020 at 8:41 PM Bartosz Golaszewski <brgl@bgdev.pl> wrote:
> > On Tue, Oct 27, 2020 at 2:54 PM Vincent Whitchurch
> > > +#ifdef CONFIG_OF
> > > +static const struct of_device_id gpio_mockup_of_match[] = {
> > > +       { .compatible = "gpio-mockup", },
> > > +       {},
> > > +};
> > > +MODULE_DEVICE_TABLE(of, gpio_mockup_of_match);
> > > +#endif
> >
> > You don't need this ifdef - of_match_ptr() will evaluate to NULL if
> > CONFIG_OF is disabled and the compiler will optimize this struct out.
> 
> It's not so. If you drop ugly ifdeffery (and I vote for that, see also
> above) the of_match_ptr() must be dropped as well.  Otherwise the
> compiler will issue the warning. So it is either all or none.

Yes, you're right.  I actually tested a !OF build before but it turns
out that the warning is disabled by default and only enabled with W=1.
I'll fix this and change the header in the next version.  Thank you.

Re: [PATCH v2] gpio: mockup: Allow probing from device tree

[Bartosz Golaszewski]

On Wed, Oct 28, 2020 at 9:24 PM Andy Shevchenko
<andy.shevchenko@gmail.com> wrote:
>
> On Wed, Oct 28, 2020 at 8:41 PM Bartosz Golaszewski <brgl@bgdev.pl> wrote:
> > On Tue, Oct 27, 2020 at 2:54 PM Vincent Whitchurch
> > <vincent.whitchurch@axis.com> wrote:
>
> ...
>
> > > +#include <linux/of.h>
> >
> > Please keep the includes ordered alphabetically.
>
> Besides the fact that that is a wrong header to be included.
> mod_devicetable.h is the correct one.
> (See also below)
>
> ...
>
> > > +#ifdef CONFIG_OF
> > > +static const struct of_device_id gpio_mockup_of_match[] = {
> > > +       { .compatible = "gpio-mockup", },
> > > +       {},
> > > +};
> > > +MODULE_DEVICE_TABLE(of, gpio_mockup_of_match);
> > > +#endif
> >
> > You don't need this ifdef - of_match_ptr() will evaluate to NULL if
> > CONFIG_OF is disabled and the compiler will optimize this struct out.
>
> It's not so. If you drop ugly ifdeffery (and I vote for that, see also
> above) the of_match_ptr() must be dropped as well.
> Otherwise the compiler will issue the warning. So it is either all or none.
>
> --
> With Best Regards,
> Andy Shevchenko

Makes sense, I'll remove this from my tree for now then. Vincent:
please send another iteration.

Bartosz

Re: [PATCH v2] gpio: mockup: Allow probing from device tree

[Andy Shevchenko]

On Wed, Oct 28, 2020 at 10:00 AM Vincent Whitchurch
<vincent.whitchurch@axis.com> wrote:
>
> Allow the mockup driver to be probed via the device tree without any
> module parameters, allowing it to be used to configure and test higher
> level drivers like the leds-gpio driver and corresponding userspace
> before actual hardware is available.

You have to officially announce a DT binding for that.


-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2] gpio: mockup: Allow probing from device tree

[Vincent Whitchurch]

On Wed, Oct 28, 2020 at 12:43:22PM +0100, Andy Shevchenko wrote:
> On Wed, Oct 28, 2020 at 10:00 AM Vincent Whitchurch
> <vincent.whitchurch@axis.com> wrote:
> > Allow the mockup driver to be probed via the device tree without any
> > module parameters, allowing it to be used to configure and test higher
> > level drivers like the leds-gpio driver and corresponding userspace
> > before actual hardware is available.
> 
> You have to officially announce a DT binding for that.

Rob Herring has earlier said that was not required for this driver.  As
I mentioned a little further down in the email you are replying to:

| Drop DT binding document, since Rob Herring was OK with not documenting
| this:
| https://lore.kernel.org/linux-devicetree/5baa1ae6.1c69fb81.847f2.3ab1@mx.google.com/