Date: Wed, 04 Jun 2014 16:31:47 +0200
Message-ID: <s5hlhtc21bg.wl%tiwai@suse.de>
From: Takashi Iwai <tiwai@suse.de>
To: Tom Gundersen <teg@jklm.no>
Cc: linux-kernel@vger.kernel.org, Ming Lei <ming.lei@canonical.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Abhay Salunke <Abhay_Salunke@dell.com>, Stefan Roese <sr@denx.de>,
        Arnd Bergmann <arnd@arndb.de>, Kay Sievers <kay@vrfy.org>
Subject: Re: [PATCH] firmware loader: allow disabling of udev as firmware loader
In-Reply-To: <s5hr43421un.wl%tiwai@suse.de>
References: <1401733474-1767-1-git-send-email-teg@jklm.no>
	<s5hr43421un.wl%tiwai@suse.de>
User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka)
 FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/24.3
 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO)
MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka")
Content-Type: text/plain; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org

At Wed, 04 Jun 2014 16:20:16 +0200,
Takashi Iwai wrote:
> 
> At Mon,  2 Jun 2014 20:24:34 +0200,
> Tom Gundersen wrote:
> > 
> > Currently (at least) the dell-rbu driver selects FW_LOADER_USER_HELPER,
> > which means that distros can't really stop loading firmware through udev
> > without breaking other users (though some have).
> > 
> > Ideally we would remove/disable the udev firmware helper in both the kernel
> > and in udev, but if we were to disable it in udev and not the kernel, the result
> > would be (seemingly) hung kernels as no one would be around to cancel firmware
> > requests.
> > 
> > This patch allows udev firmware loading to be disabled while still allowing
> > non-udev firmware loading, as done by the dell-rbu driver, to continue
> > working. This is achieved by only using the fallback mechanism when the
> > uevent is suppressed.
> > 
> > Tested with
> >     FW_LOADER_USER_HELPER=n
> >     LATTICE_ECP3_CONFIG=y
> >     DELL_RBU=y
> > and udev without the firmware loading support, but I don't have the hardware
> > to test the lattice/dell drivers, so additional testing would be appreciated.
> 
> The logic of this patch looks good to me, but the Kconfig items become
> confusing by this.  Basically what we'd need is a Kconfig item
> deciding whether to build the user helper or not, in addition to a
> Kconfig item for deciding the fallback mode of request_firmware().
> 
> What about the patch like below instead?  It's smaller and the meaning
> of Kconfig items are clearer.  (In the final form, the help text
> change you added should be included there, too.)
> 
> The only (and biggest) drawback is, however, that the user-selectable
> Kconfig would be actually renamed from CONFIG_FW_LOADER_USER_HELPER to
> CONFIG_FW_LOADER_USER_HELPER_FALLBACK.

Also, since it's deprecated in the udev upstream, let's drop "default
y", too.  (It can be another patch, though.)


Takashi
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/