Subject: Re: wl1251: NVS firmware data

From: Pali Rohár <[email-masked]>
Date: Mon, 8 Dec 2014 22:11:22 +0100

On Monday 08 December 2014 21:57:21 Greg Kroah-Hartman wrote:
> On Mon, Dec 08, 2014 at 05:47:30PM +0100, Pali Rohár wrote:
> > On Monday 08 December 2014 17:37:14 Greg Kroah-Hartman wrote:
> > > On Mon, Dec 08, 2014 at 11:18:18PM +0800, Ming Lei wrote:
> > > > On Sat, Dec 6, 2014 at 9:02 PM, Pali Rohár
> > 
> > <[email-masked]> wrote:
> > > > > 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.
> 
> You should not be loading "dynamic" firmware files with the
> firmware interface, as that's not a "firmware" file anymore,
> it's a "special binary file that my driver needs to be
> created and sent into the kernel."
> 
> Use your own custom usermode helper for stuff like this, not
> the firmware interface.  But use a binary sysfs file if you
> want, that seems to make sense for it...
> 
> greg k-h

Nokia for this problem invented its own netlink interface into 
wl1251 driver. But because it was specific for N900 device it was 
rejected for inclusion into mainline kernel.

-- 
Pali Rohár
[email-masked]