netdev - Re: [PATCH] proc: proc_create() should return true if CONFIG_PROC

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Message-ID: <15346.1424863160@warthog.procyon.org.uk>
Date:	Wed, 25 Feb 2015 11:19:20 +0000
From:	David Howells <dhowells@...hat.com>
To:	Jonathon Reinhart <jonathon.reinhart@...il.com>
Cc:	dhowells@...hat.com, Zhang Zhaolong <zhangzl2013@....com>,
	"David S. Miller" <davem@...emloft.net>,
	Linux Netdev List <netdev@...r.kernel.org>,
	viro@...iv.linux.org.uk
Subject: Re: [PATCH] proc: proc_create() should return true if CONFIG_PROC_FS is not configured

Jonathon Reinhart <jonathon.reinhart@...il.com> wrote:

> Does that even compile? proc_create() and proc_create_data() both return
> "struct proc_dir_entry *". It doesn't make sense for those macros to "return"
> anything but NULL - certainly not 1.
> 
> Besides, why shouldn't "if (!proc_create())" behave like proc_create()
> failed when
> CONFIG_PROC_FS is not enabled?  You wouldn't want the caller to start trying
> to use that ((struct proc_dir_entry *)1) would you?

It's sort of arguable.  If the proc interface is merely informational and
doesn't impact the function of a module to not be present, then, yes, having
proc_create() return some "true" value might make sense.  It's possible to
arrange things so that all the proc-related functions and data get compiled
out in such a situation by not being referenced by anything.

However, if the proc interface isn't merely functional, then the proc_create()
failure *is* cause for module loading failure.  But in that case, there should
be a Kconfig dependency on procfs and you should never use the dummy
functions.

David
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