Message-ID: <1351069857.10709.3.camel@jlt4.sipsolutions.net> (sfid-20121024_111030_112612_C162737A)
Subject: Re: [PATCH v6 4/6] wireless: use OR operation to set wiphy features
From: Johannes Berg <johannes@sipsolutions.net>
To: Kalle Valo <kvalo@adurom.com>
Cc: Bing Zhao <bzhao@marvell.com>, linux-wireless@vger.kernel.org,
	"John W. Linville" <linville@tuxdriver.com>,
	Sam Leffler <sleffler@chromium.org>,
	Amitkumar Karwar <akarwar@marvell.com>
Date: Wed, 24 Oct 2012 11:10:57 +0200
In-Reply-To: <878vawz1fq.fsf@purkki.adurom.net>
References: <1350542071-26498-1-git-send-email-bzhao@marvell.com>
	 <1350542071-26498-5-git-send-email-bzhao@marvell.com>
	 <87d308z1no.fsf@purkki.adurom.net>
	 <1351069288.10709.2.camel@jlt4.sipsolutions.net>
	 <878vawz1fq.fsf@purkki.adurom.net>
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Sender: linux-wireless-owner@vger.kernel.org

On Wed, 2012-10-24 at 12:03 +0300, Kalle Valo wrote:
> Johannes Berg <johannes@sipsolutions.net> writes:
> 
> > On Wed, 2012-10-24 at 11:59 +0300, Kalle Valo wrote:
> >
> >> Is there a way to check that drivers don't accidentally clear the flags
> >> (ie. use '=' instead '|=')? For example by adding a dummy flag and
> >> checking afterwards that it's not cleared?
> >> 
> >> I'm just worried that this detail might be too easy to miss, for example
> >> somehow I had missed this patch and noticed only when rebasing ath6kl
> >> patches.
> >
> > Yes, that should be possible, set some dummy flag in wiphy_new() and
> > test & clear it in wiphy_register()?
> 
> The tricky part is to make sure that the dummy flag won't conflict with
> a real feature flag value in the future :) 

Seems like a non-issue? If you say use 1<<31 to test, and somebody adds
1<<31, they'll find that their flag never works and will figure it out?

johannes