linux-kernel - Re: Problems loading firmware using built-in drivers with kernels that use initramfs.

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Date:	Wed, 2 Sep 2015 16:46:36 -0700
From:	"Luis R. Rodriguez" <mcgrof@...e.com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Arend van Spriel <arend@...adcom.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ming Lei <ming.lei@...onical.com>,
	Takashi Iwai <tiwai@...e.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Liam Girdwood <liam.r.girdwood@...ux.intel.com>,
	"Jie, Yang" <yang.jie@...el.com>,
	"joonas.lahtinen@...ux.intel.com" <joonas.lahtinen@...ux.intel.com>,
	Al Viro <viro@...iv.linux.org.uk>, Kay Sievers <kay@...y.org>,
	David Woodhouse <dwmw2@...radead.org>,
	lkml <linux-kernel@...r.kernel.org>,
	yalin wang <yalin.wang2010@...il.com>,
	Tom Gundersen <teg@...m.no>
Subject: Re: Problems loading firmware using built-in drivers with kernels
 that use initramfs.

On Wed, Sep 2, 2015 at 4:29 PM, Dmitry Torokhov
<dmitry.torokhov@...il.com> wrote:
> On Wed, Sep 2, 2015 at 4:22 PM, Luis R. Rodriguez <mcgrof@...e.com> wrote:
>> On Wed, Sep 02, 2015 at 04:13:51PM -0700, Dmitry Torokhov wrote:
>>> On Wed, Sep 2, 2015 at 2:03 PM, Arend van Spriel <arend@...adcom.com> wrote:
>>> > Ok. So some background why we need it in brcm80211 drivers. So as a wireless
>>> > network device driver the answer we got when asking for an event to load
>>> > firware is upon IF_UP for a registered net device. Because we try to do
>>> > things smart we query the firmware running on the device for capabilities
>>> > before we can register the net device hence we request the firmware during
>>> > probe. This may be specific to wireless drivers (Intel has same approach if
>>> > not mistaken) but I suspect there may be more.
>>>
>>> We have the same issue with input devices: before we can register one
>>> we need to set their capabilities and to know their capabilities we
>>> quite often need to load their firmware/config and query the device.
>>
>> Should Arend's driver use async probe then?
>
> What has async probe have to do with anything? We will still be
> waiting for async probes to finish before we mount rootfs so it will
> not change absolutely anything.

:) Right, its what I was alluding to as well.

>> IMHO its just as hacky as using -EPROBE_DEFER too, but its at least
>> preemptively hacky. Sadly I can't think of clear and clever way for the kernel
>> to know when firmware will be ready either...  Would userspace know? Should the
>> kernel learn this from userspace ?
>
> Yes. Given only userspace knows when firmware is available (I could
> have it on a separate device and mount it at some time). So maybe
> userpsace should simply try and scan busses for unbound devices and
> tell them to re-probe when it decides that firmware is finally
> available.

OK, the folks wanting this mechanism can implement it then. Short of
that we only have hacks.

 Luis
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