Re: [PATCH 02/24] leds: core: Add support for composing LED class device names

[Baolin Wang]

Hi Jacek,

On 7 November 2018 at 06:07, Jacek Anaszewski
<jacek.anaszewski@xxxxxxxxx> wrote:
> Add public led_compose_name() API for composing LED class device
> name basing on fwnode_handle data. The function composes device name
> according to either a new <color:function> pattern or the legacy
> <devicename:color:function> pattern. The decision on using the
> particular pattern is made basing on whether fwnode contains new
> "function" and "color" properties, or the legacy "label" proeprty.
>
> Backwards compatibility with in-driver hard-coded LED class device
> names is assured thanks to the default_desc argument.
>
> In case none of the aformentioned properties was found, then, for OF
> nodes, the node name is adopted for LED class device name.
>
> Signed-off-by: Jacek Anaszewski <jacek.anaszewski@xxxxxxxxx>
> Cc: Baolin Wang <baolin.wang@xxxxxxxxxx>
> Cc: Daniel Mack <daniel@xxxxxxxxxx>
> Cc: Dan Murphy <dmurphy@xxxxxx>
> Cc: Linus Walleij <linus.walleij@xxxxxxxxxx>
> Cc: Oleh Kravchenko <oleg@xxxxxxxxxx>
> Cc: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
> Cc: Simon Shields <simon@xxxxxxxxxxxxx>
> Cc: Xiaotong Lu <xiaotong.lu@xxxxxxxxxxxxxx>
> ---
>  Documentation/leds/leds-class.txt |  2 +-
>  drivers/leds/led-core.c           | 71 +++++++++++++++++++++++++++++++++++++++
>  include/linux/leds.h              | 32 ++++++++++++++++++
>  3 files changed, 104 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/leds/leds-class.txt b/Documentation/leds/leds-class.txt
> index 836cb16..e9009c4 100644
> --- a/Documentation/leds/leds-class.txt
> +++ b/Documentation/leds/leds-class.txt
> @@ -43,7 +43,7 @@ LED Device Naming
>
>  Is currently of the form:
>
> -"devicename:colour:function"
> +"colour:function"
>
>  There have been calls for LED properties such as colour to be exported as
>  individual led class attributes. As a solution which doesn't incur as much
> diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
> index ede4fa0..f7371fc 100644
> --- a/drivers/leds/led-core.c
> +++ b/drivers/leds/led-core.c
> @@ -16,6 +16,8 @@
>  #include <linux/list.h>
>  #include <linux/module.h>
>  #include <linux/mutex.h>
> +#include <linux/of.h>
> +#include <linux/property.h>
>  #include <linux/rwsem.h>
>  #include "leds.h"
>
> @@ -327,3 +329,72 @@ void led_sysfs_enable(struct led_classdev *led_cdev)
>         led_cdev->flags &= ~LED_SYSFS_DISABLE;
>  }
>  EXPORT_SYMBOL_GPL(led_sysfs_enable);
> +
> +static void led_parse_properties(struct fwnode_handle *fwnode,
> +                                struct led_properties *props)
> +{
> +       int ret;
> +
> +       if (!fwnode)
> +               return;
> +
> +       ret = fwnode_property_read_string(fwnode, "label", &props->label);
> +       if (!ret)
> +               return;
> +
> +       ret = fwnode_property_read_string(fwnode, "function", &props->function);
> +       if (ret)
> +               pr_info("Failed to parse function property\n");
> +
> +       ret = fwnode_property_read_string(fwnode, "color", &props->color);
> +       if (ret)
> +               pr_info("Failed to parse color property\n");

Now the color and function properties can be optional, so we should
deal with different return errors.
-EINVAL means we have not set color or function property, which means
we should not give failure message for users (maybe "not supply color
property\n") and return 0 as success.
For other errors, we should not ignore them, instead we should give
failure messages and return errors.

Tested-by: Baolin Wang <baolin.wang@xxxxxxxxxx>

> +}
> +
> +int led_compose_name(struct fwnode_handle *fwnode, const char *led_hw_name,
> +                    const char *default_desc, char *led_classdev_name)
> +{
> +       struct led_properties props = {};
> +
> +       if (!led_classdev_name)
> +               return -EINVAL;
> +
> +       led_parse_properties(fwnode, &props);
> +
> +       if (props.label) {
> +               /*
> +                * Presence of 'label' DT property implies legacy LED name,
> +                * formatted as <devicename:color:function>, with possible
> +                * section omission if doesn't apply to given device.
> +                *
> +                * If no led_hw_name has been passed, then it indicates that
> +                * DT label should be used as-is for LED class device name.
> +                * Otherwise the label is prepended with led_hw_name to compose
> +                * the final LED class device name.
> +                */
> +               if (!led_hw_name) {
> +                       strncpy(led_classdev_name, props.label,
> +                               LED_MAX_NAME_SIZE);
> +               } else {
> +                       snprintf(led_classdev_name, LED_MAX_NAME_SIZE, "%s:%s",
> +                                led_hw_name, props.label);
> +               }
> +       } else if (props.function || props.color) {
> +               snprintf(led_classdev_name, LED_MAX_NAME_SIZE, "%s:%s",
> +                        props.color ?: "", props.function ?: "");
> +       } else if (default_desc) {
> +               if (!led_hw_name) {
> +                       pr_err("Legacy LED naming requires devicename segment");
> +                       return -EINVAL;
> +               }
> +               snprintf(led_classdev_name, LED_MAX_NAME_SIZE, "%s:%s",
> +                        led_hw_name, default_desc);
> +       } else if (is_of_node(fwnode)) {
> +               strncpy(led_classdev_name, to_of_node(fwnode)->name,
> +                       LED_MAX_NAME_SIZE);
> +       } else
> +               return -EINVAL;
> +
> +       return 0;
> +}
> +EXPORT_SYMBOL_GPL(led_compose_name);
> diff --git a/include/linux/leds.h b/include/linux/leds.h
> index 646c49a..ddb4001 100644
> --- a/include/linux/leds.h
> +++ b/include/linux/leds.h
> @@ -238,6 +238,32 @@ extern void led_sysfs_disable(struct led_classdev *led_cdev);
>  extern void led_sysfs_enable(struct led_classdev *led_cdev);
>
>  /**
> + * led_compose_name - compose LED class device name
> + * @child: child fwnode_handle describing a LED,
> + *        or a group of synchronized LEDs.
> + * @led_hw_name: name of the LED controller, used when falling back to legacy
> + *              LED naming; it should be set to NULL in new LED class drivers
> + * @default_desc: default <color:function> tuple, for backwards compatibility
> + *               with in-driver hard-coded LED names used as a fallback when
> + *               "label" DT property was absent; it should be set to NULL
> + *               in new LED class drivers
> + * @led_classdev_name: composed LED class device name
> + *
> + * Create LED class device name basing on the configuration provided by the
> + * board firmware. The name can have a legacy form <devicename:color:function>,
> + * or a new form <color:function>. The latter is chosen if at least one of
> + * "color" or "function" properties is present in the fwnode, leaving the
> + * section blank if the related property is absent. The former is applied
> + * when legacy "label" property is present in the fwnode. In case none of the
> + * aformentioned properties was found, then, for OF nodes, the node name
> + * is adopted for LED class device name.
> + *
> + * Returns: 0 on success or negative error value on failure
> + */
> +extern int led_compose_name(struct fwnode_handle *child, const char *led_hw_name,
> +                           const char *default_desc, char *led_classdev_name);
> +
> +/**
>   * led_sysfs_is_disabled - check if LED sysfs interface is disabled
>   * @led_cdev: the LED to query
>   *
> @@ -414,6 +440,12 @@ struct led_platform_data {
>         struct led_info *leds;
>  };
>
> +struct led_properties {
> +       const char *color;
> +       const char *function;
> +       const char *label;
> +};
> +
>  struct gpio_desc;
>  typedef int (*gpio_blink_set_t)(struct gpio_desc *desc, int state,
>                                 unsigned long *delay_on,
> --
> 2.1.4
>



-- 
Baolin Wang
Best Regards