[PATCH v2 1/2] driver core: Introduce device_find_any_child() helper

[PATCH v2 1/2] driver core: Introduce device_find_any_child() helper

[Andy Shevchenko]

There are several places in the kernel where this kind of functionality is
being used. Provide a generic helper for such cases.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
v2: renamed method (Greg), refactored it (Rafael)
 drivers/base/core.c    | 20 ++++++++++++++++++++
 include/linux/device.h |  2 ++
 2 files changed, 22 insertions(+)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 7cd789c4985d..a519307fda60 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -3832,6 +3832,26 @@ struct device *device_find_child_by_name(struct device *parent,
 }
 EXPORT_SYMBOL_GPL(device_find_child_by_name);
 
+static int match_any(struct device *dev, void *unused)
+{
+	return 1;
+}
+
+/**
+ * device_find_any_child - device iterator for locating a child device, if any.
+ * @parent: parent struct device
+ *
+ * This is similar to the device_find_child() function above, but it
+ * returns a reference to a child device, if any.
+ *
+ * NOTE: you will need to drop the reference with put_device() after use.
+ */
+struct device *device_find_any_child(struct device *parent)
+{
+	return device_find_child(parent, NULL, match_any);
+}
+EXPORT_SYMBOL_GPL(device_find_any_child);
+
 int __init devices_init(void)
 {
 	devices_kset = kset_create_and_add("devices", &device_uevent_ops, NULL);
diff --git a/include/linux/device.h b/include/linux/device.h
index dc941997795c..424b55df0272 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -905,6 +905,8 @@ struct device *device_find_child(struct device *dev, void *data,
 				 int (*match)(struct device *dev, void *data));
 struct device *device_find_child_by_name(struct device *parent,
 					 const char *name);
+struct device *device_find_any_child(struct device *parent);
+
 int device_rename(struct device *dev, const char *new_name);
 int device_move(struct device *dev, struct device *new_parent,
 		enum dpm_order dpm_order);
-- 
2.35.1

[PATCH v2 2/2] spi: Use device_find_any_child() instead of custom approach

[Andy Shevchenko]

We have already a helper to get the first child device, use it and
drop custom approach.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
v2: added tag (Rafael)
 drivers/spi/spi.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index ea09d1b42bf6..b04be04dddfa 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -2613,11 +2613,6 @@ int spi_slave_abort(struct spi_device *spi)
 }
 EXPORT_SYMBOL_GPL(spi_slave_abort);
 
-static int match_true(struct device *dev, void *data)
-{
-	return 1;
-}
-
 static ssize_t slave_show(struct device *dev, struct device_attribute *attr,
 			  char *buf)
 {
@@ -2625,7 +2620,7 @@ static ssize_t slave_show(struct device *dev, struct device_attribute *attr,
 						   dev);
 	struct device *child;
 
-	child = device_find_child(&ctlr->dev, NULL, match_true);
+	child = device_find_any_child(&ctlr->dev);
 	return sprintf(buf, "%s\n",
 		       child ? to_spi_device(child)->modalias : NULL);
 }
@@ -2644,7 +2639,7 @@ static ssize_t slave_store(struct device *dev, struct device_attribute *attr,
 	if (rc != 1 || !name[0])
 		return -EINVAL;
 
-	child = device_find_child(&ctlr->dev, NULL, match_true);
+	child = device_find_any_child(&ctlr->dev);
 	if (child) {
 		/* Remove registered slave */
 		device_unregister(child);
-- 
2.35.1

Re: [PATCH v2 2/2] spi: Use device_find_any_child() instead of custom approach

[Mark Brown]

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On Fri, Jun 10, 2022 at 03:02:19PM +0300, Andy Shevchenko wrote:
> We have already a helper to get the first child device, use it and
> drop custom approach.

Acked-by: Mark Brown <broonie@kernel.org>

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Re: [PATCH v2 1/2] driver core: Introduce device_find_any_child() helper

[Rafael J. Wysocki]

On Fri, Jun 10, 2022 at 2:02 PM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> There are several places in the kernel where this kind of functionality is
> being used. Provide a generic helper for such cases.
>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
> v2: renamed method (Greg), refactored it (Rafael)
>  drivers/base/core.c    | 20 ++++++++++++++++++++
>  include/linux/device.h |  2 ++
>  2 files changed, 22 insertions(+)
>
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 7cd789c4985d..a519307fda60 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -3832,6 +3832,26 @@ struct device *device_find_child_by_name(struct device *parent,
>  }
>  EXPORT_SYMBOL_GPL(device_find_child_by_name);
>
> +static int match_any(struct device *dev, void *unused)
> +{
> +       return 1;
> +}
> +
> +/**
> + * device_find_any_child - device iterator for locating a child device, if any.
> + * @parent: parent struct device
> + *
> + * This is similar to the device_find_child() function above, but it
> + * returns a reference to a child device, if any.
> + *
> + * NOTE: you will need to drop the reference with put_device() after use.
> + */
> +struct device *device_find_any_child(struct device *parent)
> +{
> +       return device_find_child(parent, NULL, match_any);
> +}
> +EXPORT_SYMBOL_GPL(device_find_any_child);

I would call it device_get_any_child() to indicate the reference
counting, but that's a very minor nit.

Regardless of the above

Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

> +
>  int __init devices_init(void)
>  {
>         devices_kset = kset_create_and_add("devices", &device_uevent_ops, NULL);
> diff --git a/include/linux/device.h b/include/linux/device.h
> index dc941997795c..424b55df0272 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -905,6 +905,8 @@ struct device *device_find_child(struct device *dev, void *data,
>                                  int (*match)(struct device *dev, void *data));
>  struct device *device_find_child_by_name(struct device *parent,
>                                          const char *name);
> +struct device *device_find_any_child(struct device *parent);
> +
>  int device_rename(struct device *dev, const char *new_name);
>  int device_move(struct device *dev, struct device *new_parent,
>                 enum dpm_order dpm_order);
> --
> 2.35.1
>

Re: [PATCH v2 1/2] driver core: Introduce device_find_any_child() helper

[Greg Kroah-Hartman]

On Fri, Jun 10, 2022 at 03:02:18PM +0300, Andy Shevchenko wrote:
> There are several places in the kernel where this kind of functionality is
> being used. Provide a generic helper for such cases.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
> v2: renamed method (Greg), refactored it (Rafael)

Much nicer, thanks, I'll go queue this up now.

greg k-h