netdev - leds: netdev trigger - misleading link state indication at boot

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Message-ID: <20210413182051.GR1463@shell.armlinux.org.uk>
Date:   Tue, 13 Apr 2021 19:20:51 +0100
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Ben Whitten <ben.whitten@...il.com>, Dan Murphy <dmurphy@...com>
Cc:     linux-leds@...r.kernel.org, netdev@...r.kernel.org
Subject: leds: netdev trigger - misleading link state indication at boot

Hi,

I'm seeing some odd behaviour with the netdev trigger and some WiFi
interfaces.

When the WiFi interface has never been brought up (so is in an
operationally disabled state), if I bind a LED to the netdev
trigger, setting the device_name to the WiFi interface name and
enable the "link" property, the LED illuminates, indicating that
the WiFi device has link - but it's disabled.

If I up/down the WiFi interface, thereby returning it to the
original state, the link LED goes out.

I suspect ledtrig-netdev.c needs to check that the device is both
up (dev->flags & IFF_UP) and netif_carrier_ok(dev) both return true,
rather than just relying on netif_carrier_ok(). I don't think using
netif_running() is appropriate, as that will return true before
ndo_open() has been called to initialise the carrier state.

Agreed?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!