leds: trigger: netdev: Check offload ability on interface up

The trigger_data->hw_control indicates whether the LED is controlled by HW
offload, i.e. the PHY. The trigger_data->hw_control = can_hw_control() is
currently called only from netdev_led_attr_store(), i.e. when writing any
sysfs attribute of the netdev trigger instance associated with a PHY LED.

The can_hw_control() calls validate_net_dev() which internally calls
led_cdev->hw_control_get_device(), which is phy_led_hw_control_get_device()
for PHY LEDs. The phy_led_hw_control_get_device() returns NULL if the PHY
is not attached.

At least in case of DWMAC (STM32MP, iMX8M, ...), the PHY device is attached
only when the interface is brought up and is detached again when the
interface is brought down. In case e.g. udev rules configure the netdev
LED trigger sysfs attributes before the interface is brought up, then when
the interface is brought up, the LEDs are not blinking.

This is because trigger_data->hw_control = can_hw_control() was called
when udev wrote the sysfs attribute files, before the interface was up,
so can_hw_control() resp. validate_net_dev() returned false, and the
trigger_data->hw_control = can_hw_control() was never called again to
update the trigger_data->hw_control content and let the offload take
over the LED blinking.

Call data->hw_control = can_hw_control() from netdev_trig_notify() to
update the offload capability of the LED when the UP notification arrives.
This makes the LEDs blink after the interface is brought up.

On STM32MP13xx with RTL8211F, it is enough to have the following udev rule
in place, boot the machine with cable plugged in, and the LEDs won't work
without this patch once the interface is brought up, even if they should:
"
ACTION=="add", SUBSYSTEM=="leds", KERNEL=="stmmac-0:01:green:wan", ATTR{trigger}="netdev", ATTR{link_10}="1", ATTR{link_100}="1", ATTR{link_1000}="1", ATTR{device_name}="end0"
ACTION=="add", SUBSYSTEM=="leds", KERNEL=="stmmac-0:01:yellow:wan", ATTR{trigger}="netdev", ATTR{rx}="1", ATTR{tx}="1", ATTR{device_name}="end0"
"

Signed-off-by: Marek Vasut <marex@denx.de>
---
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Christian Marangi <ansuelsmth@gmail.com>
Cc: Christophe Roullier <christophe.roullier@foss.st.com>
Cc: Daniel Golle <daniel@makrotopia.org>
Cc: Heiner Kallweit <hkallweit1@gmail.com>
Cc: Lee Jones <lee@kernel.org>
Cc: Lukasz Majewski <lukma@denx.de>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: kernel@dh-electronics.com
Cc: linux-leds@vger.kernel.org
Cc: linux-stm32@st-md-mailman.stormreply.com
Cc: netdev@vger.kernel.org
---
 drivers/leds/trigger/ledtrig-netdev.c | 2 ++
 1 file changed, 2 insertions(+)

On Sat, 14 Dec 2024, Andrew Lunn wrote:

> On Fri, Dec 13, 2024 at 11:15:09PM +0100, Marek Vasut wrote:
> > On 10/3/24 2:06 PM, Andrew Lunn wrote:
> > > On Tue, Oct 01, 2024 at 04:45:23AM +0200, Marek Vasut wrote:
> > > > The trigger_data->hw_control indicates whether the LED is controlled by HW
> > > > offload, i.e. the PHY. The trigger_data->hw_control = can_hw_control() is
> > > > currently called only from netdev_led_attr_store(), i.e. when writing any
> > > > sysfs attribute of the netdev trigger instance associated with a PHY LED.
> > > > 
> > > > The can_hw_control() calls validate_net_dev() which internally calls
> > > > led_cdev->hw_control_get_device(), which is phy_led_hw_control_get_device()
> > > > for PHY LEDs. The phy_led_hw_control_get_device() returns NULL if the PHY
> > > > is not attached.
> > > > 
> > > > At least in case of DWMAC (STM32MP, iMX8M, ...), the PHY device is attached
> > > > only when the interface is brought up and is detached again when the
> > > > interface is brought down. In case e.g. udev rules configure the netdev
> > > > LED trigger sysfs attributes before the interface is brought up, then when
> > > > the interface is brought up, the LEDs are not blinking.
> > > > 
> > > > This is because trigger_data->hw_control = can_hw_control() was called
> > > > when udev wrote the sysfs attribute files, before the interface was up,
> > > > so can_hw_control() resp. validate_net_dev() returned false, and the
> > > > trigger_data->hw_control = can_hw_control() was never called again to
> > > > update the trigger_data->hw_control content and let the offload take
> > > > over the LED blinking.
> > > > 
> > > > Call data->hw_control = can_hw_control() from netdev_trig_notify() to
> > > > update the offload capability of the LED when the UP notification arrives.
> > > > This makes the LEDs blink after the interface is brought up.
> > > > 
> > > > On STM32MP13xx with RTL8211F, it is enough to have the following udev rule
> > > > in place, boot the machine with cable plugged in, and the LEDs won't work
> > > > without this patch once the interface is brought up, even if they should:
> > > > "
> > > > ACTION=="add", SUBSYSTEM=="leds", KERNEL=="stmmac-0:01:green:wan", ATTR{trigger}="netdev", ATTR{link_10}="1", ATTR{link_100}="1", ATTR{link_1000}="1", ATTR{device_name}="end0"
> > > > ACTION=="add", SUBSYSTEM=="leds", KERNEL=="stmmac-0:01:yellow:wan", ATTR{trigger}="netdev", ATTR{rx}="1", ATTR{tx}="1", ATTR{device_name}="end0"
> > > > "
> > > > 
> > > > Signed-off-by: Marek Vasut <marex@denx.de>
> > > 
> > > Reviewed-by: Andrew Lunn <andrew@lunn.ch>
> > Is there anything blocking this patch from being picked up ?
> 
> I think this should be going via the LED Maintainer. Please check with

It looked like the conversation was continuing.

If you have everything tied up, rather than relying on maintainers to
keep up with the branching conversations of 100's of patch-sets, it's
best to collect the tags you have and submit a [RESEND].

> It looked like the conversation was continuing.

Yes, it did, for nice to have additional functionality. But i think
the base patch is good to go, and it has my Reviewed-by:.

I expect there will be a resend coming soon :-)

	Andrew