[v2,2/5] firmware: annotate thou shalt not request fw on init or probe

Thou shalt not make firmware calls early on init or probe.

systemd already ripped support out for the usermode helper
a while ago, there are still users that require the usermode helper,
however systemd's use of the usermode helper exacerbated a long
lasting issue of the fact that we have many drivers that load
firmware on init or probe. Independent of the usermode helper
loading firmware on init or probe is a bad idea for a few reasons.

When the firmware is read directly from the filesystem by the kernel,
if the driver is built-in to the kernel the firmware may not yet be
available, for such uses one could use initramfs and stuff the firmware
inside, or one also use CONFIG_EXTRA_FIRMWARE; however not all distributions
use this, as such generally one cannot count on this. There is another
corner cases to consider, since we are accessing the firmware directly folks
cannot expect new found firmware on a filesystem after we switch off from
an initramfs with pivot_root().

Supporting such situations is possible today but fixing it for good is
really complex due to the large amount of variablity in the boot up
process.

Instead just document the expectations properly and add a grammar rule to
enable folks to check / validate / police if drivers are using the request
firmware API early on init or probe.

The SmPL rule used to check for the probe routine is loose and is
currently defined through a regexp, that can easily be extended to any
other known bus probe routine names. It also uses the new Python
iteration support which allows us to backtrack from a request_firmware*()
call back to a possible probe or init, iteratively. Without iteration
we would only be able to get reports for callers who directly use the
request_firmware*() API on the initial probe or init routine.

There are 4 offenders at this time:

mcgrof@ergon ~/linux-next (git::20160609)$ export COCCI=scripts/coccinelle/api/request_firmware.cocci
mcgrof@ergon ~/linux-next (git::20160609)$ make coccicheck MODE=report

drivers/fmc/fmc-fakedev.c: ERROR: driver call request firmware call on its init routine on line 321.
drivers/fmc/fmc-write-eeprom.c: ERROR: driver call request firmware call on its probe routine on line 136.
drivers/tty/serial/rp2.c: ERROR: driver call request firmware call on its probe routine on line 796.
drivers/tty/serial/ucc_uart.c: ERROR: driver call request firmware call on its probe routine on line 1246.

I checked and verified all these are valid reports. This list also matches
the same list as in 20150805, so we have fortunately not gotten worse.
Let's keep it that way and also fix these drivers.

v2: changes from v1 [0]:

o This now supports iteration, this extends our coverage on the report

o Update documentation and commit log to accept the fate of not being
  able to remove the usermode helper.

[0] https://lkml.kernel.org/r/1440811107-861-1-git-send-email-mcgrof@do-not-panic.com

Cc: Alessandro Rubini <rubini@gnudd.com>
Cc: Kevin Cernekee <cernekee@gmail.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Ming Lei <ming.lei@canonical.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Julia Lawall <Julia.Lawall@lip6.fr>
Cc: Gilles Muller <Gilles.Muller@lip6.fr>
Cc: Nicolas Palix <nicolas.palix@imag.fr>
Cc: Thierry Martinez <martinez@nsup.org>
Cc: Michal Marek <mmarek@suse.com>
Cc: cocci@systeme.lip6.fr
Cc: Alessandro Rubini <rubini@gnudd.com>
Cc: Kevin Cernekee <cernekee@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: linux-serial@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-serial@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
---
 Documentation/firmware_class/README                |  20 ++++
 drivers/base/Kconfig                               |   2 +-
 .../request_firmware-avoid-init-probe-init.cocci   | 130 +++++++++++++++++++++
 3 files changed, 151 insertions(+), 1 deletion(-)
 create mode 100644 scripts/coccinelle/api/request_firmware-avoid-init-probe-init.cocci

On Fri, Jun 17, 2016 at 12:54 AM, Luis R. Rodriguez <mcgrof@kernel.org> wrote:
> Thou shalt not make firmware calls early on init or probe.
>
> systemd already ripped support out for the usermode helper
> a while ago, there are still users that require the usermode helper,
> however systemd's use of the usermode helper exacerbated a long
> lasting issue of the fact that we have many drivers that load
> firmware on init or probe. Independent of the usermode helper
> loading firmware on init or probe is a bad idea for a few reasons.
>
> When the firmware is read directly from the filesystem by the kernel,
> if the driver is built-in to the kernel the firmware may not yet be
> available, for such uses one could use initramfs and stuff the firmware
> inside, or one also use CONFIG_EXTRA_FIRMWARE; however not all distributions
> use this, as such generally one cannot count on this. There is another
> corner cases to consider, since we are accessing the firmware directly folks
> cannot expect new found firmware on a filesystem after we switch off from
> an initramfs with pivot_root().
>
> Supporting such situations is possible today but fixing it for good is
> really complex due to the large amount of variablity in the boot up
> process.
>
> Instead just document the expectations properly and add a grammar rule to
> enable folks to check / validate / police if drivers are using the request
> firmware API early on init or probe.
>
> The SmPL rule used to check for the probe routine is loose and is
> currently defined through a regexp, that can easily be extended to any
> other known bus probe routine names. It also uses the new Python
> iteration support which allows us to backtrack from a request_firmware*()
> call back to a possible probe or init, iteratively. Without iteration
> we would only be able to get reports for callers who directly use the
> request_firmware*() API on the initial probe or init routine.
>
> There are 4 offenders at this time:
>
> mcgrof@ergon ~/linux-next (git::20160609)$ export COCCI=scripts/coccinelle/api/request_firmware.cocci
> mcgrof@ergon ~/linux-next (git::20160609)$ make coccicheck MODE=report
>
> drivers/fmc/fmc-fakedev.c: ERROR: driver call request firmware call on its init routine on line 321.
> drivers/fmc/fmc-write-eeprom.c: ERROR: driver call request firmware call on its probe routine on line 136.
> drivers/tty/serial/rp2.c: ERROR: driver call request firmware call on its probe routine on line 796.
> drivers/tty/serial/ucc_uart.c: ERROR: driver call request firmware call on its probe routine on line 1246.

Plus all gpu drivers which need firmware. And yes we must load them at
probe because people are generally pissed when they boot their machine
and the screen goes black. On top of that a lot of people want their
gpu drivers to be built-in, but can't ship the firmware blobs in the
kernel image because gpl. Yep, there's a bit a contradiction there ...

I think what would work is loading the different subsystems of the
driver in parallel (we already do that largely), and then if one
firmware blob isn't there yet simply stall that async worker until it
shows up. But the answers I've gotten thus far from request_firmware()
folks (well at least Greg) is don't do that ...

Is that problem still somewhere on the radar? Atm there's various
wait_for_rootfs hacks out there floating in vendor/product trees.
"Avoid at all costs" sounds like upstream prefers to not care about
android/cros in those case (yes I know most arm socs don't need
firmware, which would make it a problem fo just be a subset of all
devices).
-Daniel

> I checked and verified all these are valid reports. This list also matches
> the same list as in 20150805, so we have fortunately not gotten worse.
> Let's keep it that way and also fix these drivers.
>
> v2: changes from v1 [0]:
>
> o This now supports iteration, this extends our coverage on the report
>
> o Update documentation and commit log to accept the fate of not being
>   able to remove the usermode helper.
>
> [0] https://lkml.kernel.org/r/1440811107-861-1-git-send-email-mcgrof@do-not-panic.com
>
> Cc: Alessandro Rubini <rubini@gnudd.com>
> Cc: Kevin Cernekee <cernekee@gmail.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
> Cc: David Woodhouse <dwmw2@infradead.org>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> Cc: Ming Lei <ming.lei@canonical.com>
> Cc: Jonathan Corbet <corbet@lwn.net>
> Cc: Julia Lawall <Julia.Lawall@lip6.fr>
> Cc: Gilles Muller <Gilles.Muller@lip6.fr>
> Cc: Nicolas Palix <nicolas.palix@imag.fr>
> Cc: Thierry Martinez <martinez@nsup.org>
> Cc: Michal Marek <mmarek@suse.com>
> Cc: cocci@systeme.lip6.fr
> Cc: Alessandro Rubini <rubini@gnudd.com>
> Cc: Kevin Cernekee <cernekee@gmail.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Jiri Slaby <jslaby@suse.com>
> Cc: linux-serial@vger.kernel.org
> Cc: linux-doc@vger.kernel.org
> Cc: linux-serial@vger.kernel.org
> Cc: linuxppc-dev@lists.ozlabs.org
> Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
> ---
>  Documentation/firmware_class/README                |  20 ++++
>  drivers/base/Kconfig                               |   2 +-
>  .../request_firmware-avoid-init-probe-init.cocci   | 130 +++++++++++++++++++++
>  3 files changed, 151 insertions(+), 1 deletion(-)
>  create mode 100644 scripts/coccinelle/api/request_firmware-avoid-init-probe-init.cocci
>
> diff --git a/Documentation/firmware_class/README b/Documentation/firmware_class/README
> index cafdca8b3b15..056d1cb9d365 100644
> --- a/Documentation/firmware_class/README
> +++ b/Documentation/firmware_class/README
> @@ -93,6 +93,26 @@
>     user contexts to request firmware asynchronously, but can't be called
>     in atomic contexts.
>
> +Requirements:
> +=============
> +
> +You should avoid at all costs requesting firmware on both init and probe paths
> +of your device driver. Reason for this is the complexity needed to ensure a
> +firmware will be available for a driver early in boot through different
> +build configurations. Consider built-in drivers needing firmware early, or
> +consider a driver assuming it will only get firmware after pivot_root().
> +
> +Drivers that really need firmware early should use stuff the firmware in
> +initramfs or consider using CONFIG_EXTRA_FIRMWARE. Using initramfs is much
> +more portable to more distributions as not all distributions wish to enable
> +CONFIG_EXTRA_FIRMWARE. Should a driver require the firmware being built-in
> +it should depend on CONFIG_EXTRA_FIRMWARE. There is no current annotation for
> +requiring a firmware on initramfs.
> +
> +If you're a maintainer you can help police this with:
> +
> +$ export COCCI=scripts/coccinelle/api/request_firmware-avoid-init-probe-init.cocci
> +$ make coccicheck MODE=report
>
>   about in-kernel persistence:
>   ---------------------------
> diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
> index 98504ec99c7d..12b4f5551501 100644
> --- a/drivers/base/Kconfig
> +++ b/drivers/base/Kconfig
> @@ -152,7 +152,7 @@ config FW_LOADER_USER_HELPER
>         bool
>
>  config FW_LOADER_USER_HELPER_FALLBACK
> -       bool "Fallback user-helper invocation for firmware loading"
> +       bool "Fallback user-helper invocation for firmware loading (avoid)"
>         depends on FW_LOADER
>         select FW_LOADER_USER_HELPER
>         help
> diff --git a/scripts/coccinelle/api/request_firmware-avoid-init-probe-init.cocci b/scripts/coccinelle/api/request_firmware-avoid-init-probe-init.cocci
> new file mode 100644
> index 000000000000..cf180c59e042
> --- /dev/null
> +++ b/scripts/coccinelle/api/request_firmware-avoid-init-probe-init.cocci
> @@ -0,0 +1,130 @@
> +///
> +/// Thou shalt not request firmware on init or probe
> +///
> +// Confidence: High
> +// Copyright: (C) 2016 Luis R. Rodriguez <mcgrof@kernel.org>
> +// Copyright: (C) 2015 Julia Lawall, Inria/LIP6.
> +//
> +// GPLv2.
> +// URL: http://coccinelle.lip6.fr/
> +// Options: --no-includes --include-headers --no-show-diff
> +// Requires: 1.0.5
> +//
> +// Coccinelle 1.0.5 is required given that this uses the shiny new
> +// python iteration feature.
> +
> +virtual report
> +virtual after_start
> +
> +// -------------------------------------------------------------------------
> +
> +@initialize:python@
> +@@
> +
> +seen = set()
> +
> +def add_if_not_present(f, file, starter_var):
> +    if (f, file, starter_var) not in seen:
> +        seen.add((f, file, starter_var))
> +        it = Iteration()
> +        if file != None:
> +            it.set_files([file])
> +    it.add_virtual_rule(after_start)
> +    it.add_virtual_rule(report)
> +    it.add_virtual_identifier(fn, f)
> +    it.add_virtual_identifier(starter, starter_var)
> +    it.register()
> +
> +reported = set()
> +
> +def print_err(str, file, line):
> +    if (file, line) not in reported:
> +        reported.add((file, line))
> +       print "%s: ERROR: driver call request firmware call on its %s routine on line %d." % (file, str, line)
> +
> +@ defines_module_init@
> +declarer name module_init;
> +identifier init;
> +@@
> +
> +module_init(init);
> +
> +@ has_probe depends on defines_module_init@
> +identifier drv_calls, drv_probe;
> +type bus_driver;
> +identifier probe_op =~ "(probe)";
> +@@
> +
> +bus_driver drv_calls = {
> +       .probe_op = drv_probe,
> +};
> +
> +@hascall depends on !after_start && defines_module_init@
> +position p;
> +@@
> +
> +(
> +request_firmware@p(...)
> +|
> +request_firmware_nowait@p(...)
> +|
> +request_firmware_direct@p(...)
> +)
> +
> +@script:python@
> +init << defines_module_init.init;
> +p << hascall.p;
> +@@
> +
> +if p[0].current_element == init:
> +    print_err("init", p[0].file, int(p[0].line))
> +    cocci.include_match(False)
> +
> +@script:python@
> +drv_probe << has_probe.drv_probe;
> +p << hascall.p;
> +@@
> +
> +if p[0].current_element == drv_probe:
> +    print_err("probe", p[0].file, int(p[0].line))
> +    cocci.include_match(False)
> +
> +@script:python@
> +p << hascall.p;
> +@@
> +
> +add_if_not_present(p[0].current_element, p[0].file, p[0].line)
> +
> +@hasrecall depends on after_start@
> +position p;
> +identifier virtual.fn;
> +@@
> +
> +fn@p(...)
> +
> +@script:python@
> +init << defines_module_init.init;
> +p << hasrecall.p;
> +starter << virtual.starter;
> +@@
> +
> +if p[0].current_element == init:
> +    print_err("init", p[0].file, int(starter))
> +    cocci.include_match(False)
> +
> +@script:python@
> +drv_probe << has_probe.drv_probe;
> +p << hasrecall.p;
> +starter << virtual.starter;
> +@@
> +
> +if p[0].current_element == drv_probe:
> +    print_err("probe", p[0].file, int(starter))
> +    cocci.include_match(False)
> +
> +@script:python@
> +p << hasrecall.p;
> +starter << virtual.starter;
> +@@
> +
> +add_if_not_present(p[0].current_element, p[0].file, starter)
> --
> 2.8.2
>

On Wed, Aug 24, 2016 at 08:55:55AM +0200, Daniel Vetter wrote:
> On Fri, Jun 17, 2016 at 12:54 AM, Luis R. Rodriguez <mcgrof@kernel.org> wrote:
> > Thou shalt not make firmware calls early on init or probe.

<-- snip -->

> > There are 4 offenders at this time:
> >
> > mcgrof@ergon ~/linux-next (git::20160609)$ export COCCI=scripts/coccinelle/api/request_firmware.cocci
> > mcgrof@ergon ~/linux-next (git::20160609)$ make coccicheck MODE=report
> >
> > drivers/fmc/fmc-fakedev.c: ERROR: driver call request firmware call on its init routine on line 321.
> > drivers/fmc/fmc-write-eeprom.c: ERROR: driver call request firmware call on its probe routine on line 136.
> > drivers/tty/serial/rp2.c: ERROR: driver call request firmware call on its probe routine on line 796.
> > drivers/tty/serial/ucc_uart.c: ERROR: driver call request firmware call on its probe routine on line 1246.
> 
> Plus all gpu drivers which need firmware. And yes we must load them at
> probe

Do you have an upstream driver in mind that does this ? Is it on device
drier module probe or a DRM subsystem specific probe call of some sort ?

> because people are generally pissed when they boot their machine
> and the screen goes black. On top of that a lot of people want their
> gpu drivers to be built-in, but can't ship the firmware blobs in the
> kernel image because gpl. Yep, there's a bit a contradiction there ...

Can they use initramfs for this ?

Also just curious -- as with other subsystems, is it possible to load
a generic driver first, say vesa, and then a more enhanced one later ?
I am not saying this is ideal or am I suggesting this, I'd just like
to know the feasibility of this.

> I think what would work is loading the different subsystems of the
> driver in parallel (we already do that largely)

Init level stuff is actually pretty synchronous, and in fact both
init and probe are called serially. There are a few subsystems which
have been doing things a bit differently, but these are exceptions.

When you say we already do this largely, can you describe a bit more
precisely what you mean ?

>, and then if one
> firmware blob isn't there yet simply stall that async worker until it
> shows up.

Is this an existing framework or do you mean if we add something
generic to do this async loading of subsystems ?

> But the answers I've gotten thus far from request_firmware()
> folks (well at least Greg) is don't do that ...

Well in this patch set I'm adding myself as a MAINTAINER and I've
been extending the firmware API recently to help with a few new
features I want, I've been wanting to hear more feedback from
other's needs and I had actually not gotten much -- except
only recently with the usermode helper and reasons why some
folks thought they could not use direct firmware loading from
the fs. I'm keen to hear or more use cases and needs specially if
they have to do with improving boot time and asynchronous boot.

> Is that problem still somewhere on the radar? 

Not mine.

> Atm there's various
> wait_for_rootfs hacks out there floating in vendor/product trees.

This one I've heard about recently, and I suggested two possible
solutions, with a preference to a simply notification of when
rootfs is available from userspace.

> "Avoid at all costs" sounds like upstream prefers to not care about
> android/cros in those case (yes I know most arm socs don't need
> firmware, which would make it a problem fo just be a subset of all
> devices).

In my days of dealing with Android I learned most folks did not frankly
care too much about upstream-first model. That means things were reactive.
That's a business mind set and that's fine. However for upstream we want
what is best and to discuss. I haven't seen proposals so, so long as
we just hear of "hacks" that some folks do in vendor/product trees,
what can we do ?

In so far as async probe is concerned -- that is now upstream.

http://www.do-not-panic.com/2015/12/linux-asynchronous-probe.html

In so far as modules are concerned -- this should work without issue now, and
if there is an issue its very likely a bug in the subsystem.  As I noted in the
post, built-in support requires more love. A simple option for you to test this
is to test the two debug patches at the end there and boot. Alternatively inits
can just peg the async request for all modules. Should be an easy change, just
hadn't had a change to do it yet. Maybe its time.

I'm also trying to make more async functionality possible early in boot with
dependencies annotated somehow, and have a bit of work to help with this (refer
to recent linker tables patches) already which may even be possible to used to
facelift our old kernel init levels -- but as I've studied this I've also
observed others working on very similar problems, nothing is quite taking a
large picture of this and trying to generalize this. Its why I proposed it as a
topic for KS.

So .. I agree, let's avoid the hacks. Patches welcomed.

  Luis

On Wed, Aug 24, 2016 at 10:39 PM, Luis R. Rodriguez <mcgrof@kernel.org> wrote:
> On Wed, Aug 24, 2016 at 08:55:55AM +0200, Daniel Vetter wrote:
>> On Fri, Jun 17, 2016 at 12:54 AM, Luis R. Rodriguez <mcgrof@kernel.org> wrote:
>> > Thou shalt not make firmware calls early on init or probe.
>
> <-- snip -->
>
>> > There are 4 offenders at this time:
>> >
>> > mcgrof@ergon ~/linux-next (git::20160609)$ export COCCI=scripts/coccinelle/api/request_firmware.cocci
>> > mcgrof@ergon ~/linux-next (git::20160609)$ make coccicheck MODE=report
>> >
>> > drivers/fmc/fmc-fakedev.c: ERROR: driver call request firmware call on its init routine on line 321.
>> > drivers/fmc/fmc-write-eeprom.c: ERROR: driver call request firmware call on its probe routine on line 136.
>> > drivers/tty/serial/rp2.c: ERROR: driver call request firmware call on its probe routine on line 796.
>> > drivers/tty/serial/ucc_uart.c: ERROR: driver call request firmware call on its probe routine on line 1246.
>>
>> Plus all gpu drivers which need firmware. And yes we must load them at
>> probe
>
> Do you have an upstream driver in mind that does this ? Is it on device
> drier module probe or a DRM subsystem specific probe call of some sort ?

i915 is the one I care about for obvious reasons ;-) It's all from the
pci device probe function, but nested really deeply.

>> because people are generally pissed when they boot their machine
>> and the screen goes black. On top of that a lot of people want their
>> gpu drivers to be built-in, but can't ship the firmware blobs in the
>> kernel image because gpl. Yep, there's a bit a contradiction there ...
>
> Can they use initramfs for this ?

Apparently that's also uncool with the embedded folks. Tbh I don't
know exactly why. Also I thought initramfs is available only after
built-in drivers have finished loading, but maybe that changed.

> Also just curious -- as with other subsystems, is it possible to load
> a generic driver first, say vesa, and then a more enhanced one later ?
> I am not saying this is ideal or am I suggesting this, I'd just like
> to know the feasibility of this.

Some users want a fully running gfx stack 2s after power-on. There's
not even enough time to load an uefi or vga driver first. i915
directly initializes the gpu from power-on state on those.

>> I think what would work is loading the different subsystems of the
>> driver in parallel (we already do that largely)
>
> Init level stuff is actually pretty synchronous, and in fact both
> init and probe are called serially. There are a few subsystems which
> have been doing things a bit differently, but these are exceptions.
>
> When you say we already do this largely, can you describe a bit more
> precisely what you mean ?

Oh, this isn't subsystems as in linux device/driver model, but
different parts within the driver. We fire up a bunch of struct work
to get various bits done asynchronously.

>>, and then if one
>> firmware blob isn't there yet simply stall that async worker until it
>> shows up.
>
> Is this an existing framework or do you mean if we add something
> generic to do this async loading of subsystems ?

normal workers, and flush_work and friends to sync up. We have some
really fancy ideas for essentially async init tasks that can declare
their depencies systemd-unit file style, but that's only in the
prototype stage. We need this (eventually) since handling the ordering
correctly is getting unwieldy. But again just struct work launched
from the main pci probe function.

>> But the answers I've gotten thus far from request_firmware()
>> folks (well at least Greg) is don't do that ...
>
> Well in this patch set I'm adding myself as a MAINTAINER and I've
> been extending the firmware API recently to help with a few new
> features I want, I've been wanting to hear more feedback from
> other's needs and I had actually not gotten much -- except
> only recently with the usermode helper and reasons why some
> folks thought they could not use direct firmware loading from
> the fs. I'm keen to hear or more use cases and needs specially if
> they have to do with improving boot time and asynchronous boot.
>
>> Is that problem still somewhere on the radar?
>
> Not mine.
>
>> Atm there's various
>> wait_for_rootfs hacks out there floating in vendor/product trees.
>
> This one I've heard about recently, and I suggested two possible
> solutions, with a preference to a simply notification of when
> rootfs is available from userspace.
>
>> "Avoid at all costs" sounds like upstream prefers to not care about
>> android/cros in those case (yes I know most arm socs don't need
>> firmware, which would make it a problem fo just be a subset of all
>> devices).
>
> In my days of dealing with Android I learned most folks did not frankly
> care too much about upstream-first model. That means things were reactive.
> That's a business mind set and that's fine. However for upstream we want
> what is best and to discuss. I haven't seen proposals so, so long as
> we just hear of "hacks" that some folks do in vendor/product trees,
> what can we do ?

One of the proposals which would have worked for us died a while back:

https://lkml.org/lkml/2014/6/15/47

That's essentially what I'd like to have.

[cut discussion about async probe]

> So .. I agree, let's avoid the hacks. Patches welcomed.

Hm, this is a definite change of tack - back when I discussed this
with Greg about 2 ks ago it sounded like "don't do this". The only
thing we need is some way to wait for rootfs before we do the
request_firmware. Everything else we handle already in the kernel.
-Daniel