[linux-dvb] [PATCH] Some changes to the Kbuild help

[Michael Krufky]

Trent Piepho wrote:
> On Thu, 30 Mar 2006, Michael Krufky wrote:
> 
>>>+config VIDEO_CX88_DVB_VP3054
>>>+       bool "VP-3054 Secondary I2C Bus Support"
>>>+       default y
>>>+       depends on VIDEO_CX88_DVB_MT352 && !VIDEO_CX88_DVB_ALL_FRONTENDS
>>>+       select VIDEO_CX88_VP3054
> 
> 
> You can just use:
> depends on VIDEO_CX88_DVB_MT352
> 
> VIDEO_CX88_DVB_MT352 already pulls in the !VIDEO_CX88_DVB_ALL_FRONTENDS
> for you, as well VIDEO_CX88_DVB and so on.
> 
> This patch solves the problem just fine.  As I understand it, what you are
> doing is creating VIDEO_CX88_DVB_VP3054 as a proxy for VIDEO_CX88_VP3054, and
> making it so VIDEO_CX88_VP3054 isn't set directly by the user, but rather via
> VIDEO_CX88_DVB_VP3054.  This way VIDEO_CX88_VP3054 doesn't depend _directly_
> on VIDEO_CX88_DVB_MT352, but depends on it via the VIDEO_CX88_DVB_VP3054
> proxy, which kconfig can now display correctly.  I don't understand why this
> indirection is necessary, but it works, and that's enough for me.

The indirection is necessary, because VIDEO_CX88_VP3054 cannot both 
depend on VIDEO_CX88_DVB_MT352 (which depends on 
!VIDEO_CX88_DVB_ALL_FRONTENDS) and be selected by 
VIDEO_CX88_DVB_ALL_FRONTENDS at the same time.  I don't really know what 
that condition is called... "circular dependency paradox" ?

Anyway, I tried the following and it doesn't work because of the 
explanation above.

@@ -76,7 +76,7 @@ config VIDEO_CX88_VP3054
  config VIDEO_CX88_VP3054
  	tristate "VP-3054 Secondary I2C Bus Support"
  	default m
-	depends on DVB_MT352
+	depends on VIDEO_CX88_DVB_MT352
  	---help---
  	  This adds DVB-T support for cards based on the
  	  Connexant 2388x chip and the MT352 demodulator,

When VIDEO_CX88_DVB_ALL_FRONTENDS is selected, VIDEO_CX88_VP3054 gets 
disabled.  This is the reason for the indirection.

Cheers,

Michael Krufky