linux-kernel - Re: [PATCH 03/16] wl1251: add sysfs interface for bluetooth coexistence mode configuration

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Message-ID: <1386520563.12186.13.camel@deadeye.wl.decadent.org.uk>
Date:	Sun, 8 Dec 2013 16:36:03 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Pali Rohár <pali.rohar@...il.com>
CC:	Luciano Coelho <luca@...lho.fi>,
	"John W. Linville" <linville@...driver.com>,
	Johannes Berg <johannes@...solutions.net>,
	"David S. Miller" <davem@...emloft.net>,
	<linux-wireless@...r.kernel.org>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <freemangordon@....bg>,
	<aaro.koskinen@....fi>, <pavel@....cz>, <sre@...g0.de>,
	<joni.lapilainen@...il.com>, David Gnedt <david.gnedt@...izone.at>
Subject: Re: [PATCH 03/16] wl1251: add sysfs interface for bluetooth
 coexistence mode configuration

On Sun, 2013-12-08 at 08:55 +0100, Pali Rohár wrote:
> On Tuesday 29 October 2013 00:39:47 Ben Hutchings wrote:
> > On Sat, 2013-10-26 at 22:34 +0200, Pali Rohár wrote:
> > > From: David Gnedt <david.gnedt@...izone.at>
> > > 
> > > Port the bt_coex_mode sysfs interface from wl1251 driver
> > > version included in the Maemo Fremantle kernel to allow
> > > bt-coexistence mode configuration. This enables userspace
> > > applications to set one of the modes WL1251_BT_COEX_OFF,
> > > WL1251_BT_COEX_ENABLE and WL1251_BT_COEX_MONOAUDIO. The
> > > default mode is WL1251_BT_COEX_OFF.
> > > It should be noted that this driver always enabled
> > > bt-coexistence before and enabled bt-coexistence directly
> > > affects the receiving performance, rendering it unusable in
> > > some low-signal situations. Especially monitor mode is
> > > affected very badly with bt-coexistence enabled.
> > 
> > [...]
> > 
> > This should be implemented consistently with other drivers:
> > 
> > drivers/net/wireless/ath/ath9k/htc_drv_init.c:module_param_nam
> > ed(btcoex_enable, ath9k_htc_btcoex_enable, int, 0444);
> > drivers/net/wireless/ath/ath9k/init.c:module_param_named(btco
> > ex_enable, ath9k_btcoex_enable, int, 0444);
> > drivers/net/wireless/b43/main.c:module_param_named(btcoex,
> > modparam_btcoex, int, 0444);
> > drivers/net/wireless/ipw2x00/ipw2200.c:module_param(bt_coexis
> > t, int, 0444);
> > drivers/net/wireless/iwlegacy/common.c:module_param(bt_coex_a
> > ctive, bool, S_IRUGO);
> > drivers/net/wireless/iwlwifi/iwl-drv.c:module_param_named(bt_
> > coex_active, iwlwifi_mod_params.bt_coex_active,
> > drivers/net/wireless/ti/wlcore/sysfs.c:static
> > DEVICE_ATTR(bt_coex_state, S_IRUGO | S_IWUSR,
> > 
> > Oh, hmm, I see a problem here.
> > 
> > Ben.
> 
> So where is consitency? Each driver doing this in different way:
> btcoex_enable, btcoex, bt_coexist, bt_coex_active

Indeed, it's a bigger problem than one driver and this isn't really an
objection to your patch.  I suppose there should be an nl80211 attribute
to control this behaviour per-interface.  You or any other wireless
networking developer could work on that.

Ben.

> Reason for this usage in wl1251 is to not break existing 
> userspace applications.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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