Date: Fri, 16 Dec 2016 10:09:15 +0100
From: "Luis R. Rodriguez" <mcgrof@kernel.org>
To: =?utf-8?B?UmFmYcWCIE1pxYJlY2tp?= <zajec5@gmail.com>
Cc: "Luis R. Rodriguez" <mcgrof@kernel.org>, gregkh@linuxfoundation.org,
        ming.lei@canonical.com, daniel.wagner@bmw-carit.de, teg@jklm.no,
        mchehab@osg.samsung.com, linux-kernel@vger.kernel.org,
        markivx@codeaurora.org, stephen.boyd@linaro.org, broonie@kernel.org,
        zohar@linux.vnet.ibm.com, tiwai@suse.de, johannes@sipsolutions.net,
        chunkeey@googlemail.com, hauke@hauke-m.de, jwboyer@fedoraproject.org,
        dmitry.torokhov@gmail.com, dwmw2@infradead.org, jslaby@suse.com,
        torvalds@linux-foundation.org, luto@amacapital.net,
        fengguang.wu@intel.com, rpurdie@rpsys.net, j.anaszewski@samsung.com,
        Abhay_Salunke@dell.com, Julia.Lawall@lip6.fr, Gilles.Muller@lip6.fr,
        nicolas.palix@imag.fr, dhowells@redhat.com, bjorn.andersson@linaro.org,
        arend.vanspriel@broadcom.com, kvalo@codeaurora.org
Subject: Re: [PATCH 3/5] firmware: revamp firmware documentation
Message-ID: <20161216090915.GL13946@wotan.suse.de>
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On Tue, Dec 13, 2016 at 08:26:41AM +0100, Rafał Miłecki wrote:
> On 12/13/2016 04:08 AM, Luis R. Rodriguez wrote:
> > Understanding this code is getting out of control without any
> > notes. Give the firmware_class driver a much needed documentation love,
> > and while at it convert it to the new sphinx documentation format.
> 
> It does help to understand the class/API, thank you!

Glad it is helping!

> > +Even if you have these needs there are a few reasons why you may not be
> > +able to make use of built-in firmware:
> > +
> > +* Legalese - firmware is non-GPL compatible
> > +* Some firmware may be optional
> > +* Firmware upgrades are possible, therefore a new firmware would implicate
> > +  a complete firmware rebuild.
> 
> Could it be you meant "kernel rebuild" or "vmlinux rebuild" here?

Heh, yes... thanks, fixed!

> > diff --git a/Documentation/driver-api/firmware/fallback-mechanisms.rst b/Documentation/driver-api/firmware/fallback-mechanisms.rst
> > new file mode 100644
> > index 000000000000..edce1d76ce29
> > --- /dev/null
> > +++ b/Documentation/driver-api/firmware/fallback-mechanisms.rst
> > @@ -0,0 +1,195 @@
> > +===================
> > +Fallback mechanisms
> > +===================
> > +
> > +A fallback mechanism is supported to allow to overcome failures to do a direct
> > +filesystem lookup on the root filesystem or when the firmware simply cannot be
> > +installed for practical reasons on the root filesystem. The kernel
> > +configuration options related to supporting the firmware fallback mechanism are:
> > +
> > +  * CONFIG_FW_LOADER_USER_HELPER: enables building the firmware fallback
> > +    mechanism. Most distributions enable this option today. If enabled but
> > +    CONFIG_FW_LOADER_USER_HELPER_FALLBACK is disabled, only the custom fallback
> > +    mechanism is available and for the request_firmware_nowait() call.
> > +  * CONFIG_FW_LOADER_USER_HELPER_FALLBACK: force enables each request to
> > +    enable the kobject uevent fallback mechanism on all firmare API calls
> > +    except request_firmware_direct(). Most distributions disable this option
> > +    today. The call request_firmware_nowait() allows for one alternative
> > +    fallback mechanism: if this kconfig option is enabled and your second
> > +    argument to request_firmware_nowait(), uevent, is set to false you are
> > +    informing the kernel that you have a custom fallback mechanism and it will
> > +    manually load the firmware. Read below for more details.
> 
> Yeah, it really asks for API simplification ;)

So up next once this is done is the new revamp with an extensible firmware API.

  Luis