linux-kernel - Re: patch "firmware loader: allow disabling of udev as firmware loader" added to driver-core tree

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Message-ID: <CAKocOONv97=XvciQCT3qJ-e01YVGmJsz0e-N9P2iJrsBw8eeCQ@mail.gmail.com>
Date:	Thu, 7 Aug 2014 07:23:47 -0600
From:	Shuah Khan <shuahkhan@...il.com>
To:	Takashi Iwai <tiwai@...e.de>
Cc:	Jean-Michel Hautbois <jhautbois@...il.com>, B_B_Singh@...l.com,
	Greg KH <gregkh@...uxfoundation.org>,
	Arnd Bergmann <arnd@...db.de>, Kay Sievers <kay@...y.org>,
	Ming Lei <ming.lei@...onical.com>, Stefan Roese <sr@...x.de>,
	Tom Gundersen <teg@...m.no>, Stuart_Hayes@...l.com,
	Srinivas_G_Gowda@...l.com,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: patch "firmware loader: allow disabling of udev as firmware
 loader" added to driver-core tree

On Thu, Aug 7, 2014 at 1:57 AM, Takashi Iwai <tiwai@...e.de> wrote:
>> >> Hm?  3.16 doesn't contain my patch yet.  It's merged for 3.17-rc1.
>> >
>> > Oh, you are right of course, I am on upstream kernel and I have your
>> > patch. I don't mean your match is causing the issue though ;-).
>> >
>>
>> I think this is what is going on and this patch is the cause:
>> fw_load_from_user_helper() is a stub that returns -ENOENT with this
>> patch.
>
> ... unless specifying the new Kconfig
> CONFIG_FW_LOADER_USER_HELPER_FALLBACK=y.  This is exactly the purpose
> of the commit.

Right - I figured that is the intent.

>
>> As a result, in _request_firmware() after fw_get_filesystem_firmware()
>> fails to find the file, fw_load_from_user_helper() gets called and it
>> returns right
>> away with -ENOENT.
>>
>> In some cases if rootfs mount is in progress, fw_load_from_user_helper()
>> steps into load the firmware.
>
> When a module in initrd requires a firmware, it should be put in
> initrd, too.

Right. This is something drivers have to watch out for with this change.

-- Shuah
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