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    SubjectRe: [RFC PATCH v6 02/11] leds: add function to configure hardware controlled LED
    > +In SUPPORTED hw_control_configure() should return 0 or 1 if the LED driver supports the
    > +requested blink mode (flags) or not.

    -EOPNOTSUPP might be clearer.


    > +In ZERO hw_control_configure() should return 0 with success operation or error.
    > +
    > +The unsigned long flag is specific to the trigger and change across them. It's in the LED
    > +driver interest know how to elaborate this flag and to declare support for a
    > +particular trigger. For this exact reason explicit support for the specific
    > +trigger is mandatory or the driver returns -EOPNOTSUPP if asked to enter offload mode
    > +with a not supported trigger.
    > +If the driver returns -EOPNOTSUPP on hw_control_configure(), the trigger activation will
    > +fail as the driver doesn't support that specific offload trigger or doesn't know
    > +how to handle the provided flags.
    > +
    > Known Issues
    > ============
    >
    > diff --git a/include/linux/leds.h b/include/linux/leds.h
    > index 09ff1dc6f48d..b5aad67fecfb 100644
    > --- a/include/linux/leds.h
    > +++ b/include/linux/leds.h
    > @@ -73,6 +73,16 @@ enum led_blink_modes {
    > SOFTWARE_HARDWARE_CONTROLLED,
    > };
    >
    > +#ifdef CONFIG_LEDS_HARDWARE_CONTROL
    > +enum blink_mode_cmd {
    > + BLINK_MODE_ENABLE, /* Enable the hardware blink mode */
    > + BLINK_MODE_DISABLE, /* Disable the hardware blink mode */
    > + BLINK_MODE_READ, /* Read the status of the hardware blink mode */
    > + BLINK_MODE_SUPPORTED, /* Ask the driver if the hardware blink mode is supported */
    > + BLINK_MODE_ZERO, /* Disable any hardware blink active */
    > +};
    > +#endif

    Skip the #ifdef. The enum itself takes no space if never used, and it
    makes the driver simpler if they always exist.

    > +
    > struct led_classdev {
    > const char *name;
    > unsigned int brightness;
    > @@ -185,6 +195,17 @@ struct led_classdev {
    > * the old status but that is not mandatory and also putting it off is accepted.
    > */
    > int (*hw_control_stop)(struct led_classdev *led_cdev);
    > + /* This will be used to configure the various blink modes LED support in hardware
    > + * mode.
    > + * The LED driver require to support the active trigger and will elaborate the
    > + * unsigned long flag and do the operation based on the provided cmd.
    > + * Current operation are enable,disable,supported and status.
    > + * A trigger will use this to enable or disable the asked blink mode, check the
    > + * status of the blink mode or ask if the blink mode can run in hardware mode.
    > + */
    > + int (*hw_control_configure)(struct led_classdev *led_cdev,
    > + unsigned long flag,
    > + enum blink_mode_cmd cmd);
    > #endif
    > #endif
    >
    > @@ -454,6 +475,24 @@ static inline void *led_get_trigger_data(struct led_classdev *led_cdev)
    > return led_cdev->trigger_data;
    > }
    >
    > +#ifdef CONFIG_LEDS_HARDWARE_CONTROL
    > +static inline bool led_trigger_blink_mode_is_supported(struct led_classdev *led_cdev,
    > + unsigned long flag)
    > +{
    > + int ret;
    > +
    > + /* Sanity check: make sure led support hw mode */
    > + if (led_cdev->blink_mode == SOFTWARE_CONTROLLED)
    > + return false;
    > +
    > + ret = led_cdev->hw_control_configure(led_cdev, flag, BLINK_MODE_SUPPORTED);
    > + if (ret > 0)
    > + return true;
    > +
    > + return false;
    > +}
    > +#endif

    Please add a version which returns false when
    CONFIG_LEDS_HARDWARE_CONTROL is disabled.

    Does this actually need to be an inline function?

    Andrew

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