Re: [PATCH 2/6] wl1251: Use request_firmware_prefer_user() for loading NVS calibration data

From: "Pali Rohár" <pali.rohar@gmail.com>
To: Kalle Valo <kvalo@codeaurora.org>
Cc: Ming Lei <ming.lei@canonical.com>,
	"Luis R. Rodriguez" <mcgrof@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	David Gnedt <david.gnedt@davizone.at>,
	Michal Kazior <michal.kazior@tieto.com>,
	Daniel Wagner <wagi@monom.org>, Tony Lindgren <tony@atomide.com>,
	Sebastian Reichel <sre@kernel.org>, Pavel Machek <pavel@ucw.cz>,
	Ivaylo Dimitrov <ivo.g.dimitrov.75@gmail.com>,
	Aaro Koskinen <aaro.koskinen@iki.fi>,
	Grazvydas Ignotas <notasas@gmail.com>,
	linux-kernel@vger.kernel.org, linux-wireless@vger.kernel.org,
	netdev@vger.kernel.org
Subject: Re: [PATCH 2/6] wl1251: Use request_firmware_prefer_user() for loading NVS calibration data
Date: Fri, 27 Jan 2017 10:43:42 +0100	[thread overview]
Message-ID: <20170127094342.GC24223@pali> (raw)
In-Reply-To: <87tw8lnei3.fsf@codeaurora.org>

On Friday 27 January 2017 09:33:40 Kalle Valo wrote:
> Pali Rohár <pali.rohar@gmail.com> writes:
> 
> > NVS calibration data for wl1251 are model specific. Every one device with
> > wl1251 chip has different and calibrated in factory.
> >
> > Not all wl1251 chips have own EEPROM where are calibration data stored. And
> > in that case there is no "standard" place. Every device has stored them on
> > different place (some in rootfs file, some in dedicated nand partition,
> > some in another proprietary structure).
> >
> > Kernel wl1251 driver cannot support every one different storage decided by
> > device manufacture so it will use request_firmware_prefer_user() call for
> > loading NVS calibration data and userspace helper will be responsible to
> > prepare correct data.
> >
> > In case userspace helper fails request_firmware_prefer_user() still try to
> > load data file directly from VFS as fallback mechanism.
> >
> > On Nokia N900 device which has wl1251 chip, NVS calibration data are stored
> > in CAL nand partition. CAL is proprietary Nokia key/value format for nand
> > devices.
> >
> > With this patch it is finally possible to load correct model specific NVS
> > calibration data for Nokia N900.
> >
> > Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
> > ---
> >  drivers/net/wireless/ti/wl1251/Kconfig |    1 +
> >  drivers/net/wireless/ti/wl1251/main.c  |    2 +-
> >  2 files changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/wireless/ti/wl1251/Kconfig b/drivers/net/wireless/ti/wl1251/Kconfig
> > index 7142ccf..affe154 100644
> > --- a/drivers/net/wireless/ti/wl1251/Kconfig
> > +++ b/drivers/net/wireless/ti/wl1251/Kconfig
> > @@ -2,6 +2,7 @@ config WL1251
> >  	tristate "TI wl1251 driver support"
> >  	depends on MAC80211
> >  	select FW_LOADER
> > +	select FW_LOADER_USER_HELPER
> >  	select CRC7
> >  	---help---
> >  	  This will enable TI wl1251 driver support. The drivers make
> > diff --git a/drivers/net/wireless/ti/wl1251/main.c b/drivers/net/wireless/ti/wl1251/main.c
> > index 208f062..24f8866 100644
> > --- a/drivers/net/wireless/ti/wl1251/main.c
> > +++ b/drivers/net/wireless/ti/wl1251/main.c
> > @@ -110,7 +110,7 @@ static int wl1251_fetch_nvs(struct wl1251 *wl)
> >  	struct device *dev = wiphy_dev(wl->hw->wiphy);
> >  	int ret;
> >  
> > -	ret = request_firmware(&fw, WL1251_NVS_NAME, dev);
> > +	ret = request_firmware_prefer_user(&fw, WL1251_NVS_NAME, dev);
> 
> I don't see the need for this. Just remove the default nvs file from
> filesystem and the fallback user helper will be always used, right?

It is part of linux-firmware repository. And already part of all
previous versions of linux-firmware packages in lot of linux
distributions. So removing it is not possible...

> Like we discussed earlier, the default nvs file should not be used by
> normal users.

But already is and we need to deal with this fact.

-- 
Pali Rohár
pali.rohar@gmail.com