Re: [PATCH] Some changes to the Kbuild help

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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

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