Date:	Mon, 08 Dec 2014 13:26:53 -0600
From:	Dan Williams <dcbw@...hat.com>
To:	Pali Rohár <pali.rohar@...il.com>
Cc:	Marcel Holtmann <marcel@...tmann.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ming Lei <ming.lei@...onical.com>, Pavel Machek <pavel@....cz>,
	"John W. Linville" <linville@...driver.com>,
	Grazvydas Ignotas <notasas@...il.com>,
	"linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
	Network Development <netdev@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>,
	Aaro Koskinen <aaro.koskinen@....fi>,
	Kalle Valo <kvalo@...rom.com>,
	Sebastian Reichel <sre@...g0.de>,
	David Gnedt <david.gnedt@...izone.at>
Subject: Re: wl1251: NVS firmware data

On Mon, 2014-12-08 at 20:15 +0100, Pali Rohár wrote:
> On Monday 08 December 2014 19:50:17 Marcel Holtmann wrote:
> > Hi Pali,
> > 
> > >>>>>> On Saturday 06 December 2014 13:49:54 Pavel Machek
> > >>>>>> wrote: /**
> > >>>>>> 
> > >>>>>> + * request_firmware_prefer_user: - prefer usermode
> > >>>>>> helper for loading firmware + * @firmware_p: pointer to
> > >>>>>> firmware image
> > >>>>>> + * @name: name of firmware file
> > >>>>>> + * @device: device for which firmware is being loaded
> > >>>>>> + *
> > >>>>>> + * This function works pretty much like
> > >>>>>> request_firmware(), but it prefer + * usermode helper.
> > >>>>>> If usermode helper fails then it fallback to direct
> > >>>>>> access. + * Usefull for dynamic or model specific
> > >>>>>> firmware data. + **/
> > >>>>>> +int request_firmware_prefer_user(const struct firmware
> > >>>>>> **firmware_p, +                           const char
> > >>>>>> *name, struct device *device) +{
> > >>>>>> +       int ret;
> > >>>>>> +       __module_get(THIS_MODULE);
> > >>>>>> +       ret = _request_firmware(firmware_p, name,
> > >>>>>> device, +                               FW_OPT_UEVENT
> > >>>>>> | FW_OPT_PREFER_USER); +      
> > >>>>>> module_put(THIS_MODULE); +       return ret;
> > >>>>>> +}
> > >>>>>> +EXPORT_SYMBOL_GPL(request_firmware_prefer_user);
> > >>>>> 
> > >>>>> I'd like to introduce request_firmware_user() which only
> > >>>>> requests firmware from user space, and this way is
> > >>>>> simpler and more flexible since we have
> > >>>>> request_firmware_direct() already.
> > >>>> 
> > >>>> Why would a driver care about what program provides the
> > >>>> firmware?  It shouldn't at all, and we want to get rid of
> > >>>> the userspace firmware loader, not encourage drivers to
> > >>>> use it "exclusively" at all.
> > >>> 
> > >>> Do not remove it! Without userspace firmware loader it is
> > >>> impossible to load dynamic firmware files.
> > >> 
> > >> why is this dynamic in the first place. It does not sound
> > >> like dynamic data to me at all. This is like the WiFi MAC
> > >> address(es) or Bluetooth BD_ADDR. They are all static
> > >> information. The only difference is that they are on the
> > >> host accessibly filesystem or storage and not on the
> > >> device itself.
> > >> 
> > >> To be honest, for Bluetooth we solved this now. If the
> > >> device is missing key information like the calibration
> > >> data or BD_ADDR, then it comes up unconfigured. A
> > >> userspace process can then go and load the right data into
> > >> it and then the device becomes available as Bluetooth
> > >> device.
> > >> 
> > >> Trying to use request_firmware to load some random data and
> > >> insist on going through userspace helper for that sounds
> > >> crazy to me. Especially since we are trying hard to get
> > >> away from the userspace loader. Forcing to keep it for new
> > >> stuff sounds backwards to me.
> > >> 
> > >> With the special Nokia partition in mind, why hasn't this
> > >> been turned into a mountable filesystem or into a
> > >> driver/subsystem that can access the data direct from the
> > >> kernel. I advocated for this some time ago. Maybe there
> > >> should be a special subsystem for access to these factory
> > >> persistent information that drivers then just can access.
> > >> I seem to remember that some systems provide these via
> > >> ACPI. Why does the ARM platform has to be special here?
> > >> 
> > >> And the problem of getting Ethernet and WiFi MAC address
> > >> and Bluetooth BD_ADDR comes up many many times. Why not
> > >> have something generic here. And don't tell me
> > >> request_firmware is that generic solution ;)
> > >> 
> > >> Regards
> > >> 
> > >> Marcel
> > > 
> > > Hi Marcel. I think you did not understand this problem. This
> > > discussion is not about mac address. Please read email
> > > thread again and if there are some unclear pars, then ask.
> > > Thanks!
> > 
> > I think that I pretty clearly understand the problem.
> > Calibration data, MAC address, what is the difference? For me
> > this is all the same. It is data that is specific to a device
> > or type of devices and it is stored somewhere else. In most
> > cases in some immutable memory/flash area.
> > 
> 
> Those calibration data (in form of binary NVS firmware file) 
> needs to be sent to wl1251 chip. Mac address is not needed at 
> this step (and kernel generate some random if is not provided).
> 
> (Just to note wl1271 driver loads both MAC address and NVS data 
> via one firmware file which is prepared by userspace, but this 
> discussion is about wl1251...)
> 
> > What you want is access to this data since the kernel driver
> > needs it. Do I get this so far ;)
> > 
> 
> Yes, we need to provide NVS data to kernel when kernel ask for 
> them.
> 
> > So my take is that request_firmware is not the right way to
> > get this data. Or more precisely make sure that this data is
> > available to kernel drivers. And what I am seeing here is
> > that instead of actually solving the bigger problem, we just
> > hack around it with request_firmware. Now surprisingly the
> > request_firmware loads files directly from the kernel and all
> > the hacks do not work anymore.
> > 
> > Regards
> > 
> > Marcel
> 
> Just read emails again...
> 
> Our problem is:
> 
> linux-firmware.git tree provides two binary firmware files:
> 
> ti-connectivity/wl1251-fw.bin
> ti-connectivity/wl1251-nvs.bin
> 
> First is firmware file, second NVS file with generic calibration 
> data. Kernel driver wl1251 now loads both firmware files via 
> request_firmware. Generic calibration data are enough for wl1251 
> chip (it should work). But devices have own calibration data 
> stored somewhere else.
> 
> On Nokia N900 NVS data are generated on-the-fly from some bytes 
> from CAL (/dev/mtd1), from state of cellular network and from 
> some other regulation settings.
> 
> So I think that files stored in linux-firmware.git tree (which 
> are also installed into /lib/firmware/) should be loaded with 
> request_firmware function. Or not? Do you think something else? 
> What other developers think?
> 
> I'm against kernel driver for CAL (/dev/mtd1) for more reasons:
> 
> 1) we have userspace open source code, but licensed under GPLv3. 
> And until kernel change license, we cannot include it.
> 
> 2) NVS data are (probably) not in one place, plus they depends on 
> something other.
> 
> 3) If manufacture XYZ create new device with its own storage 
> format of calibration data this means that correct solution for 
> XYZ is also to implement new kernel fs driver for its own format. 
> Do you really want to have in kernel all those drivers for all 
> different (proprietary) storage formats?
> 
> 4) It does not help us with existence of generic file 
> /lib/firmware/ti-connectivity/wl1251-nvs.bin which comes from 
> linux-firmware.git tree.

a) change driver to prefer a new "wl1251-nvs-n900.bin" file, but fall
back to "wl1251-nvs.bin" if the first one isn't present
b) have a "wl1251-cal-nvs-update" service that, if wl1521-nvs-n900.bin
is *not* present mounts the CAL MTD, reads the data, writes it out into
wl1521-nvs-n900.bin, and the rmmod/modprobes the driver

and done?  Stuff that's not N900 just wouldn't ship the update service
and would proceed like none of this happened.

Dan


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