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Date: Wed, 3 Jan 2024 14:56:30 +0100
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Subject: Re: [PATCH] r8169: fix building with CONFIG_LEDS_CLASS=m
To: Arnd Bergmann <arnd@arndb.de>, Arnd Bergmann <arnd@kernel.org>,
 "David S . Miller" <davem@davemloft.net>, Eric Dumazet
 <edumazet@google.com>, Jakub Kicinski <kuba@kernel.org>,
 Paolo Abeni <pabeni@redhat.com>
Cc: Netdev <netdev@vger.kernel.org>, linux-kernel@vger.kernel.org,
 "linux-leds@vger.kernel.org" <linux-leds@vger.kernel.org>,
 Lee Jones <lee@kernel.org>
References: <20240103102630.3770242-1-arnd@kernel.org>
 <5b0a6150-8043-4de7-980f-54020a3e7981@gmail.com>
 <b310230b-f20b-489a-97ed-908df193a942@app.fastmail.com>
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From: Heiner Kallweit <hkallweit1@gmail.com>
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In-Reply-To: <b310230b-f20b-489a-97ed-908df193a942@app.fastmail.com>
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On 03.01.2024 13:45, Arnd Bergmann wrote:
> On Wed, Jan 3, 2024, at 12:33, Heiner Kallweit wrote:
>> On 03.01.2024 11:26, Arnd Bergmann wrote:
>>> From: Arnd Bergmann <arnd@arndb.de>
>>>
>>> When r8169 is built-in but the LED support is a loadable module, the
>>> new code to drive the LED now causes a link failure:
>>>
>>> ld: drivers/net/ethernet/realtek/r8169_leds.o: in function `rtl8168_init_leds':
>>> r8169_leds.c:(.text+0x36c): undefined reference to `devm_led_classdev_register_ext'
>>>
>>> Add a Kconfig dependency to prevent the broken configuration but still
>>> allow having the network code built-in as long as CONFIG_LEDS_TRIGGER_NETDEV
>>> is disabled, regardless of CONFIG_LEDS_CLASS.
>>>
>> The proposed change is more of a workaround IMO. A proper fix (in LED 
>> subsystem)
>> has been submitted, but it's not reviewed/applied yet. And I don't 
>> think building
>> r8169 should depend on support for an optional feature.
>> This fix would also allow to remove Kconfig dependencies similar to the 
>> one
>> proposed here from other drivers. Link to submitted fix:
>>
>> https://lore.kernel.org/linux-leds/0f6f432b-c650-4bb8-a1b5-fe3372804d52@gmail.com/T/#u
> 
> I think that is a much worse workaround, as this just leads to
> a feature silently not working even when it is enabled (as loadable
> module), and hiding other dependency problems where drivers
> actually require the LED support to do something useful.
> 
Whether implicit dependency detection is considered a bad thing,
may depend on personal taste. However I see your point.

> IS_REACHABLE() is pretty much always a bad idea because of this.
> 
> If you want the LED support in r8169_leds to be optional, I would
> suggest adding a separate Kconfig symbol for that, either user
> visible or hidden, and have the correct Kconfig dependencies
> for the new symbol, something like the change below (untested).
> 
Sounds good, as this would also allow to omit compiling r8169_leds.c
if LEDS_CLASS isn't reachable. I'll give it a try.

>      Arnd
> 
Heiner

> 8<---
> diff --git a/drivers/net/ethernet/realtek/Kconfig b/drivers/net/ethernet/realtek/Kconfig
> index fd3f18b328de..b54aae30b3c1 100644
> --- a/drivers/net/ethernet/realtek/Kconfig
> +++ b/drivers/net/ethernet/realtek/Kconfig
> @@ -114,4 +114,9 @@ config R8169
>           To compile this driver as a module, choose M here: the module
>           will be called r8169.  This is recommended.
>  
> +config R8169_LEDS
> +       def_bool y
> +       depends on LEDS_TRIGGER_NETDEV && R8169
> +       depends on !(R8169=y && LEDS_CLASS=m)
> +
>  endif # NET_VENDOR_REALTEK
> diff --git a/drivers/net/ethernet/realtek/Makefile b/drivers/net/ethernet/realtek/Makefile
> index adff9ebfbf2c..635491d8826e 100644
> --- a/drivers/net/ethernet/realtek/Makefile
> +++ b/drivers/net/ethernet/realtek/Makefile
> @@ -6,8 +6,6 @@
>  obj-$(CONFIG_8139CP) += 8139cp.o
>  obj-$(CONFIG_8139TOO) += 8139too.o
>  obj-$(CONFIG_ATP) += atp.o
> -r8169-objs += r8169_main.o r8169_firmware.o r8169_phy_config.o
> -ifdef CONFIG_LEDS_TRIGGER_NETDEV
> -r8169-objs += r8169_leds.o
> -endif
> +r8169-y += r8169_main.o r8169_firmware.o r8169_phy_config.o
> +r8169-$(CONFIG_R8169_LEDS) += r8169_leds.o
>  obj-$(CONFIG_R8169) += r8169.o
> diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
> index 05ba5f743af2..f3321299b2fa 100644
> --- a/drivers/net/ethernet/realtek/r8169_main.c
> +++ b/drivers/net/ethernet/realtek/r8169_main.c
> @@ -5356,11 +5356,10 @@ static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
>         if (rc)
>                 return rc;
>  
> -#if IS_REACHABLE(CONFIG_LEDS_CLASS) && IS_ENABLED(CONFIG_LEDS_TRIGGER_NETDEV)
> -       if (tp->mac_version > RTL_GIGA_MAC_VER_06 &&
> +       if (IS_ENABLED(CONFIG_R8169_LEDS) &&
> +           tp->mac_version > RTL_GIGA_MAC_VER_06 &&
>             tp->mac_version < RTL_GIGA_MAC_VER_61)
>                 rtl8168_init_leds(dev);
> -#endif
>  
>         netdev_info(dev, "%s, %pM, XID %03x, IRQ %d\n",
>                     rtl_chip_infos[chipset].name, dev->dev_addr, xid, tp->irq);