Messages in this thread | | | Subject | Re: Weird Kconfig condition (IPV6 [=n] || IPV6 [=n]=n) | From | Andreas Ziegler <> | Date | Mon, 14 Sep 2015 12:57:19 +0200 |
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Hi,
On 09/14/2015 10:41, Mason wrote: > Hello, > > I did make menuconfig in v4.2 > > In the help for CONFIG_CRYPTO_HMAC, I have > > │ Selected by: IP_SCTP [=n] && NET [=y] && INET [=y] && (IPV6 [=n] || IPV6 [=n]=n) || INET_AH [=n] && NET [=y] && INET [=y] || \ │ > │ INET_ESP [=n] && NET [=y] && INET [=y] || INET6_AH [=n] && NET [=y] && INET [=y] && IPV6 [=n] || INET6_ESP [=n] && NET [=y] && INET [=y]\ │ > │ && IPV6 [=n] || SCTP_COOKIE_HMAC_MD5 [=n] && NET [=y] && IP_SCTP [=n] && SCTP_COOKIE_HMAC_MD5 [=n] || SCTP_COOKIE_HMAC_SHA1 [=n] && \ │ > │ NET [=y] && IP_SCTP [=n] && SCTP_COOKIE_HMAC_SHA1 [=n] || CIFS [=n] && NETWORK_FILESYSTEMS [=y] && INET [=y] || TRUSTED_KEYS [=n] && \ │ > │ KEYS [=y] && TCG_TPM [=n] || ENCRYPTED_KEYS [=n] && KEYS [=y] || IMA [=n] && INTEGRITY [=n] || EVM [=n] && INTEGRITY [=n] || \ │ > │ CRYPTO_DRBG_HMAC [=y] && CRYPTO [=y] && CRYPTO_DRBG_MENU [=m] || CRYPTO_DEV_OMAP_SHAM [=n] && CRYPTO [=y] && CRYPTO_HW [=y] && \ │ > │ ARCH_OMAP2PLUS [=n] || CRYPTO_DEV_QAT [=n] && CRYPTO [=y] && CRYPTO_HW [=y] │ > > > What does (IPV6 [=n] || IPV6 [=n]=n) mean? > Is this a bug in my configuration?
No, this comes from the definition of IP_SCTP in net/sctp/Kconfig. menuconfig IP_SCTP tristate "The SCTP Protocol" depends on INET depends on IPV6 || IPV6=n ^^^^^^^^^^^^^^
This weird-looking condition has the effect that: - if IPV6 is disabled, IP_SCTP can be anything ("y","m" or "n") - if IPV6 is enabled to "y", IP_SCTP can also be set to anything. - (and this is the reason why it's there:) if IPV6 is a module ("m"), IP_SCTP can only be "m" or "n".
In a way, the "depends on" does not only reference the symbol, but also keeps track of the 'state' of the symbol it references, such that if the dependency (here: IPV6) is to be built as a loadable module only, the dependant feature can also only be built as a loadable module.
I can't find the Documentation for that at the moment, but I'm sure that I read this at some point, maybe also only on a mailing list...
Regards,
Andreas
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