Re: [PATCH v2 2/3] usb: Add LED trigger for USB host activity

[Michal Sojka <sojka@merica.cz>]

Hi Bryan,

thanks for the review. See some comments below.

On Sat, Aug 23 2014, Bryan Wu wrote:
> On Fri, Aug 22, 2014 at 5:08 PM, Michal Sojka <sojka@merica.cz> wrote:
>> With this patch, USB host activity can be signaled by blinking a LED.
>>
>> This should work with all host controllers. Tested only with musb.
>>
>> Signed-off-by: Michal Sojka <sojka@merica.cz>
>> ---
>>  drivers/usb/core/Kconfig  |  9 +++++++++
>>  drivers/usb/core/Makefile |  1 +
>>  drivers/usb/core/hcd.c    |  2 ++
>>  drivers/usb/core/led.c    | 38 ++++++++++++++++++++++++++++++++++++++
>>  include/linux/usb/hcd.h   |  6 ++++++
>>  5 files changed, 56 insertions(+)
>>  create mode 100644 drivers/usb/core/led.c
>>
>> diff --git a/drivers/usb/core/Kconfig b/drivers/usb/core/Kconfig
>> index 1060657..8295f65 100644
>> --- a/drivers/usb/core/Kconfig
>> +++ b/drivers/usb/core/Kconfig
>> @@ -90,3 +90,12 @@ config USB_OTG_FSM
>>           Implements OTG Finite State Machine as specified in On-The-Go
>>           and Embedded Host Supplement to the USB Revision 2.0 Specification.
>>
>> +config USB_HOST_LED
>> +       bool "USB Host LED Trigger"
>> +       depends on LEDS_CLASS
>> +       select LEDS_TRIGGERS
>> +       help
>> +         This option adds a LED trigger for USB host controllers.
>> +
>> +         Say Y here if you are working on a system with led-class supported
>> +         LEDs and you want to use them as USB host activity indicators.
>> diff --git a/drivers/usb/core/Makefile b/drivers/usb/core/Makefile
>> index 2f6f932..324c8c9 100644
>> --- a/drivers/usb/core/Makefile
>> +++ b/drivers/usb/core/Makefile
>> @@ -9,5 +9,6 @@ usbcore-y += port.o
>>
>>  usbcore-$(CONFIG_PCI)          += hcd-pci.o
>>  usbcore-$(CONFIG_ACPI)         += usb-acpi.o
>> +usbcore-$(CONFIG_USB_HOST_LED) += led.o
>>
>>  obj-$(CONFIG_USB)              += usbcore.o
>> diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
>> index 487abcf..46d9f3a 100644
>> --- a/drivers/usb/core/hcd.c
>> +++ b/drivers/usb/core/hcd.c
>> @@ -1664,6 +1664,8 @@ static void __usb_hcd_giveback_urb(struct urb *urb)
>>         usbmon_urb_complete(&hcd->self, urb, status);
>>         usb_anchor_suspend_wakeups(anchor);
>>         usb_unanchor_urb(urb);
>> +       if (status == 0)
>> +               usb_hcd_led_activity();
>>
>>         /* pass ownership to the completion handler */
>>         urb->status = status;
>> diff --git a/drivers/usb/core/led.c b/drivers/usb/core/led.c
>> new file mode 100644
>> index 0000000..49ff76c
>> --- /dev/null
>> +++ b/drivers/usb/core/led.c
>> @@ -0,0 +1,38 @@
>> +/*
>> + * LED Trigger for USB Host Activity
>> + *
>> + * Copyright 2014 Michal Sojka <sojka@merica.cz>
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>> + *
>> + */
>> +
>> +#include <linux/module.h>
>> +#include <linux/kernel.h>
>> +#include <linux/init.h>
>> +#include <linux/leds.h>
>> +#include <linux/usb/hcd.h>
>> +
>> +#define BLINK_DELAY 30
>> +
>> +DEFINE_LED_TRIGGER(ledtrig_usb_hcd);
>
> Add one more trigger named ledtrig_usb_gadget
>
>> +static unsigned long usb_hcd_blink_delay = BLINK_DELAY;
>> +
>> +void usb_hcd_led_activity(void)
>
> Give an input parameter like emum usb_led_event.
> USB_LED_EVENT_HOST = 0
> USB_LED_EVENT_GADGET = 1
>
>
>> +{
>
> Add case for USB_LED_EVENT_HOST:
>> +       led_trigger_blink_oneshot(ledtrig_usb_hcd,
>> +                                 &usb_hcd_blink_delay, &usb_hcd_blink_delay, 0);
>
> Add case for USB_LED_EVENT_GADGET:
>  led_trigger_blink_oneshot(ledtrig_usb_gadget,
>                              &usb_gadget_blink_delay,
> &usb_gadget_blink_delay, 0);
>
>> +}
>> +
>> +int __init ledtrig_usb_hcd_init(void)
>> +{
>> +       led_trigger_register_simple("usb-host", &ledtrig_usb_hcd);
> register one more trigger for gadget.

This way, the code will be full of #ifdefs. Is the following really what
you want? If you want to have it without #ifdefs, then I don't think it
is a good idea to offer users the usb-gadget trigger on systems without
usb gadget support.

#define BLINK_DELAY 30

static unsigned long usb_blink_delay = BLINK_DELAY;

enum usb_led_event {
	USB_LED_EVENT_HOST = 0,
	USB_LED_EVENT_GADGET = 1,
};

#ifdef CONFIG_USB_GADGET_LED
DEFINE_LED_TRIGGER(ledtrig_usbgadget);
#endif
#ifdef CONFIG_USB_HOST_LED
DEFINE_LED_TRIGGER(ledtrig_usb_hcd);
#endif

void usb_led_activity(enum usb_led_event ev)
{
	struct led_trigger *trig;

	switch (ev) {
#ifdef CONFIG_USB_GADGET_LED
	case USB_LED_EVENT_GADGET: trig = ledtrig_usb_gadget; break;
#endif
#ifdef CONFIG_USB_HOST_LED
	case USB_LED_EVENT_HOST:   trig = ledtrig_usb_hcd; break;
#endif
	default:;
	}
	led_trigger_blink_oneshot(trig, &usb_blink_delay, &usb_blink_delay, 0);
}
EXPORT_SYMBOL(usb_led_activity);


int __init ledtrig_usb_init(void)
{
#ifdef CONFIG_USB_GADGET_LED
	led_trigger_register_simple("usb-gadget", &ledtrig_usbgadget);
#endif
#ifdef CONFIG_USB_HOST_LED
	led_trigger_register_simple("usb-host", &ledtrig_usb_hcd);
#endif
	return 0;
}

void __exit ledtrig_usb_exit(void)
{
#ifdef CONFIG_USB_GADGET_LED
	led_trigger_unregister_simple(ledtrig_usbgadget);
#endif
#ifdef CONFIG_USB_HOST_LED
	led_trigger_unregister_simple(ledtrig_usb_hcd);
#endif
}


-Michal