Re: [PATCH can-next v4] can: add tx/rx LED trigger support

[Marc Kleine-Budde <mkl@pengutronix.de>]

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On 08/01/2012 12:05 AM, Fabio Baltieri wrote:
> This patch implements the functions to add two LED triggers, named
> <ifname>-tx and <ifname>-rx, to a canbus device driver.
> 
> Triggers are called from specific handlers by each CAN device driver and
> can be disabled altogether with a Kconfig option.
> 
> The implementation keeps the LED on when the interface is UP and blinks
> the LED on network activity at a configurable rate.
> 
> This only supports can-dev based drivers, as it uses some support field
> in the can_priv structure.
> 
> Supported drivers should call can_led_init() and can_led_event() as
> needed.
> 
> Cleanup is handled automatically by devres, so no *_exit function is
> needed.
> 
> Supported events are:
> - CAN_LED_EVENT_OPEN: turn on tx/rx LEDs
> - CAN_LED_EVENT_STOP: turn off tx/rx LEDs
> - CAN_LED_EVENT_TX: trigger tx LED blink
> - CAN_LED_EVENT_RX: trigger tx LED blink
> 
> Cc: Oliver Hartkopp <socketcan@hartkopp.net>
> Cc: Wolfgang Grandegger <wg@grandegger.com>
> Cc: Marc Kleine-Budde <mkl@pengutronix.de>
> Signed-off-by: Fabio Baltieri <fabio.baltieri@gmail.com>
> ---
> 
> Hi!
> 
> So, here is the v4.
> 
> Changes against v3:
> - add a netdev_err message in kasprintf error path
> - implement a devres_alloc release function to de-allocate strings and trigger
> - can_led_exit is now unneeded and gone
> 
> Is that what you had in mind Marc?

Yes, that's it. Can you add a devm_ prefix to can_led_init() please.

> I like the devres implementation, as callers don't have to care about exit
> function anymore... still it looks like a bit of an hack to me.

No :)

> Also, I made an initial version with the four pointers in a separate can_led
> struct to be allocated as a payload of devres_alloc - but I think this one
> looks cleaner and is more cache-friendly.

If you allocate the 4 pointers in a separate struct you only save 3
points, as you need the pointer to the struct anyways.

> What you think about this?

Looks good. See comment inline,

Marc

>  drivers/net/can/Kconfig  |  12 ++++++
>  drivers/net/can/Makefile |   2 +
>  drivers/net/can/led.c    | 102 +++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/can/dev.h  |   8 ++++
>  include/linux/can/led.h  |  34 ++++++++++++++++
>  5 files changed, 158 insertions(+)
>  create mode 100644 drivers/net/can/led.c
>  create mode 100644 include/linux/can/led.h
> 
> diff --git a/drivers/net/can/Kconfig b/drivers/net/can/Kconfig
> index bb709fd..19dec19 100644
> --- a/drivers/net/can/Kconfig
> +++ b/drivers/net/can/Kconfig
> @@ -54,6 +54,18 @@ config CAN_CALC_BITTIMING
>  	  arguments "tq", "prop_seg", "phase_seg1", "phase_seg2" and "sjw".
>  	  If unsure, say Y.
>  
> +config CAN_LEDS
> +	bool "Enable LED triggers for Netlink based drivers"
> +	depends on CAN_DEV
> +	depends on LEDS_CLASS
> +	select LEDS_TRIGGERS
> +	---help---
> +	  This option adds two LED triggers for packet receive and transmit
> +	  events on each supported CAN device.
> +
> +	  Say Y here if you are working on a system with led-class supported
> +	  LEDs and you want to use them as canbus activity indicators.
> +
>  config CAN_AT91
>  	tristate "Atmel AT91 onchip CAN controller"
>  	depends on CAN_DEV && (ARCH_AT91SAM9263 || ARCH_AT91SAM9X5)
> diff --git a/drivers/net/can/Makefile b/drivers/net/can/Makefile
> index 938be37..24ee98b 100644
> --- a/drivers/net/can/Makefile
> +++ b/drivers/net/can/Makefile
> @@ -8,6 +8,8 @@ obj-$(CONFIG_CAN_SLCAN)		+= slcan.o
>  obj-$(CONFIG_CAN_DEV)		+= can-dev.o
>  can-dev-y			:= dev.o
>  
> +can-dev-$(CONFIG_CAN_LEDS)	+= led.o
> +
>  obj-y				+= usb/
>  obj-y				+= softing/
>  
> diff --git a/drivers/net/can/led.c b/drivers/net/can/led.c
> new file mode 100644
> index 0000000..4fa8a47
> --- /dev/null
> +++ b/drivers/net/can/led.c
> @@ -0,0 +1,102 @@
> +/*
> + * Copyright 2012, Fabio Baltieri <fabio.baltieri@gmail.com>
> + *
> + * 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/device.h>
> +#include <linux/kernel.h>
> +#include <linux/slab.h>
> +#include <linux/netdevice.h>
> +#include <linux/can/dev.h>
> +
> +#include <linux/can/led.h>
> +
> +static unsigned long led_delay = 50;
> +module_param(led_delay, ulong, 0644);
> +MODULE_PARM_DESC(led_delay,
> +		"blink delay time for activity leds (msecs, default: 50).");
> +
> +/*
> + * Trigger a LED event in response to a CAN device event
> + */
> +void can_led_event(struct net_device *netdev, enum can_led_event event)
> +{
> +	struct can_priv *priv = netdev_priv(netdev);
> +
> +	switch (event) {
> +	case CAN_LED_EVENT_OPEN:
> +		led_trigger_event(priv->tx_led_trig, LED_FULL);
> +		led_trigger_event(priv->rx_led_trig, LED_FULL);
> +		break;
> +	case CAN_LED_EVENT_STOP:
> +		led_trigger_event(priv->tx_led_trig, LED_OFF);
> +		led_trigger_event(priv->rx_led_trig, LED_OFF);
> +		break;
> +	case CAN_LED_EVENT_TX:
> +		if (led_delay)
> +			led_trigger_blink_oneshot(priv->tx_led_trig,
> +						  &led_delay, &led_delay, 1);
> +		break;
> +	case CAN_LED_EVENT_RX:
> +		if (led_delay)
> +			led_trigger_blink_oneshot(priv->rx_led_trig,
> +						  &led_delay, &led_delay, 1);
> +		break;
> +	}
> +}
> +EXPORT_SYMBOL_GPL(can_led_event);
> +
> +static void can_led_release(struct device *gendev, void *res)
> +{
> +	struct can_priv *priv = netdev_priv(to_net_dev(gendev));
> +
> +	led_trigger_unregister_simple(priv->tx_led_trig);
> +	led_trigger_unregister_simple(priv->rx_led_trig);
> +
> +	kfree(priv->tx_led_trig_name);
> +	kfree(priv->rx_led_trig_name);
> +}
> +
> +/*
> + * Register CAN LED triggers for a CAN device
> + *
> + * This is normally called from a driver's probe function
> + */
> +void can_led_init(struct net_device *netdev)
> +{
> +	struct can_priv *priv = netdev_priv(netdev);
> +	void *res;
> +
> +	res = devres_alloc(can_led_release, 0, GFP_KERNEL);
                                            ^
I'm not really sure if this is working. For example, pinctrl [1]
allocates a double pointer here. The res pointer here and in
can_led_release simply points to invalid memory. But as long as you
don't dereference it, it should work.

[1] http://lxr.free-electrons.com/source/drivers/pinctrl/core.c#L862

> +	if (!res)
> +		goto err_out;
> +
> +	priv->tx_led_trig_name = kasprintf(GFP_KERNEL, "%s-tx", netdev->name);
> +	if (!priv->tx_led_trig_name)
> +		goto err_out;
> +
> +	priv->rx_led_trig_name = kasprintf(GFP_KERNEL, "%s-rx", netdev->name);
> +	if (!priv->rx_led_trig_name)
> +		goto err_out_rx;
> +
> +	led_trigger_register_simple(priv->tx_led_trig_name,
> +				    &priv->tx_led_trig);
> +	led_trigger_register_simple(priv->rx_led_trig_name,
> +				    &priv->rx_led_trig);
> +
> +	devres_add(&netdev->dev, res);
> +
> +	return;
> +
> +err_out_rx:
> +	kfree(priv->tx_led_trig_name);
> +	priv->tx_led_trig_name = NULL;
> +err_out:
> +	netdev_err(netdev, "cannot register LED triggers\n");
> +	devres_free(res);
> +}
> +EXPORT_SYMBOL_GPL(can_led_init);

Marc
-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
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