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[PATCH v3 04/11] gpiolib: provide gpio_device_find_by_label()

Bartosz Golaszewski posted 11 patches 2 years, 4 months ago
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[PATCH v3 04/11] gpiolib: provide gpio_device_find_by_label()
Posted by Bartosz Golaszewski 2 years, 4 months ago 
From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

By far the most common way of looking up GPIO devices is using their
label. Provide a helpers for that to avoid every user implementing their
own matching function.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
---
 drivers/gpio/gpiolib.c      | 21 +++++++++++++++++++++
 include/linux/gpio/driver.h |  1 +
 2 files changed, 22 insertions(+)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 0371d23f0a46..9f20311e4c1a 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -20,6 +20,7 @@
 #include <linux/seq_file.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
+#include <linux/string.h>
 
 #include <linux/gpio.h>
 #include <linux/gpio/driver.h>
@@ -1081,6 +1082,26 @@ struct gpio_device *gpio_device_find(void *data,
 }
 EXPORT_SYMBOL_GPL(gpio_device_find);
 
+static int gpio_chip_match_by_label(struct gpio_chip *gc, void *label)
+{
+	return gc->label && !strcmp(gc->label, label);
+}
+
+/**
+ * gpio_device_find_by_label() - wrapper around gpio_device_find() finding the
+ *                               GPIO device by its backing chip's label
+ * @label: Label to lookup
+ *
+ * Returns:
+ * Reference to the GPIO device or NULL. Reference must be released with
+ * gpio_device_put().
+ */
+struct gpio_device *gpio_device_find_by_label(const char *label)
+{
+	return gpio_device_find((void *)label, gpio_chip_match_by_label);
+}
+EXPORT_SYMBOL_GPL(gpio_device_find_by_label);
+
 static int gpiochip_match_name(struct gpio_chip *gc, void *data)
 {
 	const char *name = data;
diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index 6ad1f1a8ef2e..24996cba6465 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -610,6 +610,7 @@ struct gpio_chip *gpiochip_find(void *data,
 
 struct gpio_device *gpio_device_find(void *data,
 				int (*match)(struct gpio_chip *gc, void *data));
+struct gpio_device *gpio_device_find_by_label(const char *label);
 
 struct gpio_device *gpio_device_get(struct gpio_device *gdev);
 void gpio_device_put(struct gpio_device *gdev);
-- 
2.39.2
Re: [PATCH v3 04/11] gpiolib: provide gpio_device_find_by_label()
Posted by Andy Shevchenko 2 years, 4 months ago 
On Fri, Sep 15, 2023 at 05:03:19PM +0200, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> 
> By far the most common way of looking up GPIO devices is using their
> label. Provide a helpers for that to avoid every user implementing their
> own matching function.

...

> +static int gpio_chip_match_by_label(struct gpio_chip *gc, void *label)
> +{
> +	return gc->label && !strcmp(gc->label, label);
> +}

I am still wondering if we can oblige providers to have label to be non-empty.

-- 
With Best Regards,
Andy Shevchenko
Re: [PATCH v3 04/11] gpiolib: provide gpio_device_find_by_label()
Posted by Bartosz Golaszewski 2 years, 4 months ago 
On Mon, Sep 18, 2023 at 9:19 AM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> On Fri, Sep 15, 2023 at 05:03:19PM +0200, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> >
> > By far the most common way of looking up GPIO devices is using their
> > label. Provide a helpers for that to avoid every user implementing their
> > own matching function.
>
> ...
>
> > +static int gpio_chip_match_by_label(struct gpio_chip *gc, void *label)
> > +{
> > +     return gc->label && !strcmp(gc->label, label);
> > +}
>
> I am still wondering if we can oblige providers to have label to be non-empty.
>

Of course we can. Just bail out of gpiochip_add_data_with_key() if it
is. But that's material for a different patch.

Bart
Re: [PATCH v3 04/11] gpiolib: provide gpio_device_find_by_label()
Posted by Andy Shevchenko 2 years, 4 months ago 
On Wed, Sep 27, 2023 at 01:22:36PM +0200, Bartosz Golaszewski wrote:
> On Mon, Sep 18, 2023 at 9:19 AM Andy Shevchenko
> <andriy.shevchenko@linux.intel.com> wrote:
> >
> > On Fri, Sep 15, 2023 at 05:03:19PM +0200, Bartosz Golaszewski wrote:
> > > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> > >
> > > By far the most common way of looking up GPIO devices is using their
> > > label. Provide a helpers for that to avoid every user implementing their
> > > own matching function.

...

> > > +static int gpio_chip_match_by_label(struct gpio_chip *gc, void *label)
> > > +{
> > > +     return gc->label && !strcmp(gc->label, label);
> > > +}
> >
> > I am still wondering if we can oblige providers to have label to be non-empty.
> 
> Of course we can. Just bail out of gpiochip_add_data_with_key() if it
> is. But that's material for a different patch.

Yes, but my point here is that
1) the current users are already following this requirement;
2) the enforcement can be done explicitly somewhere (in the register function).

Is the 1) incorrect assumption?

-- 
With Best Regards,
Andy Shevchenko
Re: [PATCH v3 04/11] gpiolib: provide gpio_device_find_by_label()
Posted by Bartosz Golaszewski 2 years, 4 months ago 
On Wed, Sep 27, 2023 at 2:33 PM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> On Wed, Sep 27, 2023 at 01:22:36PM +0200, Bartosz Golaszewski wrote:
> > On Mon, Sep 18, 2023 at 9:19 AM Andy Shevchenko
> > <andriy.shevchenko@linux.intel.com> wrote:
> > >
> > > On Fri, Sep 15, 2023 at 05:03:19PM +0200, Bartosz Golaszewski wrote:
> > > > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> > > >
> > > > By far the most common way of looking up GPIO devices is using their
> > > > label. Provide a helpers for that to avoid every user implementing their
> > > > own matching function.
>
> ...
>
> > > > +static int gpio_chip_match_by_label(struct gpio_chip *gc, void *label)
> > > > +{
> > > > +     return gc->label && !strcmp(gc->label, label);
> > > > +}
> > >
> > > I am still wondering if we can oblige providers to have label to be non-empty.
> >
> > Of course we can. Just bail out of gpiochip_add_data_with_key() if it
> > is. But that's material for a different patch.
>
> Yes, but my point here is that
> 1) the current users are already following this requirement;
> 2) the enforcement can be done explicitly somewhere (in the register function).
>
> Is the 1) incorrect assumption?
>

I remember doing a quick glance over GPIO providers and it looks like
ALL of them set the label. But I may have missed something. I would
start with a warning.

Bart
Re: [PATCH v3 04/11] gpiolib: provide gpio_device_find_by_label()
Posted by Andy Shevchenko 2 years, 4 months ago 
On Wed, Sep 27, 2023 at 02:42:28PM +0200, Bartosz Golaszewski wrote:
> On Wed, Sep 27, 2023 at 2:33 PM Andy Shevchenko
> <andriy.shevchenko@linux.intel.com> wrote:
> > On Wed, Sep 27, 2023 at 01:22:36PM +0200, Bartosz Golaszewski wrote:
> > > On Mon, Sep 18, 2023 at 9:19 AM Andy Shevchenko
> > > <andriy.shevchenko@linux.intel.com> wrote:
> > > > On Fri, Sep 15, 2023 at 05:03:19PM +0200, Bartosz Golaszewski wrote:
> > > > > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

...

> > > > > +static int gpio_chip_match_by_label(struct gpio_chip *gc, void *label)
> > > > > +{
> > > > > +     return gc->label && !strcmp(gc->label, label);
> > > > > +}
> > > >
> > > > I am still wondering if we can oblige providers to have label to be non-empty.
> > >
> > > Of course we can. Just bail out of gpiochip_add_data_with_key() if it
> > > is. But that's material for a different patch.
> >
> > Yes, but my point here is that
> > 1) the current users are already following this requirement;
> > 2) the enforcement can be done explicitly somewhere (in the register function).
> >
> > Is the 1) incorrect assumption?
> 
> I remember doing a quick glance over GPIO providers and it looks like
> ALL of them set the label. But I may have missed something. I would
> start with a warning.

For now I would drop the NULL check. We will have a few weeks to see
if somebody screams about. Meanwhile we can add the real error message
patch if no-one complains.

-- 
With Best Regards,
Andy Shevchenko
Re: [PATCH v3 04/11] gpiolib: provide gpio_device_find_by_label()
Posted by Bartosz Golaszewski 2 years, 4 months ago 
On Wed, Sep 27, 2023 at 3:48 PM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> On Wed, Sep 27, 2023 at 02:42:28PM +0200, Bartosz Golaszewski wrote:
> > On Wed, Sep 27, 2023 at 2:33 PM Andy Shevchenko
> > <andriy.shevchenko@linux.intel.com> wrote:
> > > On Wed, Sep 27, 2023 at 01:22:36PM +0200, Bartosz Golaszewski wrote:
> > > > On Mon, Sep 18, 2023 at 9:19 AM Andy Shevchenko
> > > > <andriy.shevchenko@linux.intel.com> wrote:
> > > > > On Fri, Sep 15, 2023 at 05:03:19PM +0200, Bartosz Golaszewski wrote:
> > > > > > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
>
> ...
>
> > > > > > +static int gpio_chip_match_by_label(struct gpio_chip *gc, void *label)
> > > > > > +{
> > > > > > +     return gc->label && !strcmp(gc->label, label);
> > > > > > +}
> > > > >
> > > > > I am still wondering if we can oblige providers to have label to be non-empty.
> > > >
> > > > Of course we can. Just bail out of gpiochip_add_data_with_key() if it
> > > > is. But that's material for a different patch.
> > >
> > > Yes, but my point here is that
> > > 1) the current users are already following this requirement;
> > > 2) the enforcement can be done explicitly somewhere (in the register function).
> > >
> > > Is the 1) incorrect assumption?
> >
> > I remember doing a quick glance over GPIO providers and it looks like
> > ALL of them set the label. But I may have missed something. I would
> > start with a warning.
>
> For now I would drop the NULL check. We will have a few weeks to see
> if somebody screams about. Meanwhile we can add the real error message
> patch if no-one complains.

No, I'm not going to potentially break stuff like that as a way to
detect bugs. That's not a hot path, we're not gaining much. Let's add
a warning first, wait for some time, make it an error and then remove
the check.

Bart

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