Re: [build bug] drivers/built-in.o: In function `rt2x00leds_resume': : undefined reference to `led_classdev_resume'

[Ingo Molnar <mingo@elte.hu>]

* David Miller <davem@davemloft.net> wrote:

> This was reported elsewhere as well.
> 
> I was sure that the patch below fixed it.
> 
> I don't understand how it can still fail, unless the problem is that 
> selecting "FOO" does not take care to enable any dependencies of 
> "FOO".

yeah, i think that's a fundamental property of select: it does _not_ 
select the sub-dependencies. randconfig found that combination rather 
well it seems:

 # CONFIG_IWLWIFI_LEDS is not set
 # CONFIG_IWL4965_LEDS is not set
 # CONFIG_IWL3945_LEDS is not set
 CONFIG_RT2X00_LIB_LEDS=y
 # CONFIG_RT61PCI_LEDS is not set
 CONFIG_RT73USB_LEDS=y
 # CONFIG_NEW_LEDS is not set
 CONFIG_LEDS_CLASS=y

this weakness of select is the major reason why "select is evil" has 
been propagated.

personally i always considered this a Kconfig bug - although it's 
probably not an easy issue to solve. (what if there are conflicts? What 
if a driver's select choice disables another driver, without the user 
being openly aware of this side-effect?)

the patch below fixes it here but it's still kind of a band-aid - what 
if the Kconfig structure of LEDS get modified - does that have to be 
propagated to all LEDS using drivers? I dont think this necessity of 
open-coded dependency resolution is maintainable in the long run.

	Ingo

----------------->
Subject: rt2x00: leds fix
From: Ingo Molnar <mingo@elte.hu>
Date: Fri Apr 25 09:41:26 CEST 2008

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 drivers/net/wireless/rt2x00/Kconfig |    5 +++++
 1 file changed, 5 insertions(+)

Index: linux/drivers/net/wireless/rt2x00/Kconfig
===================================================================
--- linux.orig/drivers/net/wireless/rt2x00/Kconfig
+++ linux/drivers/net/wireless/rt2x00/Kconfig
@@ -62,6 +62,7 @@ config RT2400PCI_LEDS
 	bool "RT2400 leds support"
 	depends on RT2400PCI
 	select LEDS_CLASS
+	select NEW_LEDS
 	select RT2X00_LIB_LEDS
 	---help---
 	  This adds support for led triggers provided my mac80211.
@@ -89,6 +90,7 @@ config RT2500PCI_LEDS
 	bool "RT2500 leds support"
 	depends on RT2500PCI
 	select LEDS_CLASS
+	select NEW_LEDS
 	select RT2X00_LIB_LEDS
 	---help---
 	  This adds support for led triggers provided my mac80211.
@@ -118,6 +120,7 @@ config RT61PCI_LEDS
 	bool "RT61 leds support"
 	depends on RT61PCI
 	select LEDS_CLASS
+	select NEW_LEDS
 	select RT2X00_LIB_LEDS
 	---help---
 	  This adds support for led triggers provided my mac80211.
@@ -135,6 +138,7 @@ config RT2500USB_LEDS
 	bool "RT2500 leds support"
 	depends on RT2500USB
 	select LEDS_CLASS
+	select NEW_LEDS
 	select RT2X00_LIB_LEDS
 	---help---
 	  This adds support for led triggers provided my mac80211.
@@ -154,6 +158,7 @@ config RT73USB_LEDS
 	bool "RT73 leds support"
 	depends on RT73USB
 	select LEDS_CLASS
+	select NEW_LEDS
 	select RT2X00_LIB_LEDS
 	---help---
 	  This adds support for led triggers provided my mac80211.