On Thu, Jun 5, 2014 at 10:32 PM, Tom Gundersen <t...@jklm.no> wrote: > On Thu, Jun 5, 2014 at 4:24 PM, Ming Lei <ming....@canonical.com> wrote: >> On Thu, Jun 5, 2014 at 10:05 PM, Takashi Iwai <ti...@suse.de> wrote: >>> At Thu, 5 Jun 2014 21:59:52 +0800, >>> Ming Lei wrote: >>>> >>>> On Thu, Jun 5, 2014 at 9:47 PM, Takashi Iwai <ti...@suse.de> wrote: >>>> > At Thu, 5 Jun 2014 21:31:56 +0800, >>>> > Ming Lei wrote: >>>> >> >>>> >> On Thu, Jun 5, 2014 at 8:25 PM, Tom Gundersen <t...@jklm.no> wrote: >>>> >> > >>>> >> > On 5 Jun 2014 14:18, "Ming Lei" <ming....@canonical.com> wrote: >>>> >> >> >>>> >> >> On Wed, Jun 4, 2014 at 11:48 PM, Takashi Iwai <ti...@suse.de> wrote: >>>> >> >> > [The patch was originally proposed by Tom Gundersen, and rewritten >>>> >> >> > afterwards by me; most of changelogs below borrowed from Tom's >>>> >> >> > original patch -- tiwai] >>>> >> >> > >>>> >> >> > 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. >>>> >> >> > >>>> >> >> > The patch renames the user-selectable Kconfig from >>>> >> >> > FW_LOADER_USER_HELPER >>>> >> >> > to FW_LOADER_USER_HELPER_FALLBACK, and the former is >>>> >> >> > reverse-selected >>>> >> >> > by the latter or the drivers that need userhelper like dell-rbu. >>>> >> >> > >>>> >> >> > Also, the "default y" is removed together with this change, since >>>> >> >> > it's >>>> >> >> > been deprecated in udev upstream, thus rather better to disable it >>>> >> >> > nowadays. >>>> >> >> > >>>> >> >> > 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. >>>> >> >> > >>>> >> >> > Reviewed-by: Tom Gundersen <t...@jklm.no> >>>> >> >> > Cc: Ming Lei <ming....@canonical.com> >>>> >> >> > Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org> >>>> >> >> > Cc: Abhay Salunke <abhay_salu...@dell.com> >>>> >> >> > Cc: Stefan Roese <s...@denx.de> >>>> >> >> > Cc: Arnd Bergmann <a...@arndb.de> >>>> >> >> > Cc: Kay Sievers <k...@vrfy.org> >>>> >> >> > Signed-off-by: Takashi Iwai <ti...@suse.de> >>>> >> >> > --- >>>> >> >> > drivers/base/Kconfig | 10 ++++++++-- >>>> >> >> > drivers/base/firmware_class.c | 15 ++++++++++----- >>>> >> >> > include/linux/firmware.h | 2 +- >>>> >> >> > 3 files changed, 19 insertions(+), 8 deletions(-) >>>> >> >> > >>>> >> >> > diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig >>>> >> >> > index 8fa8deab6449..d0bb32e4c416 100644 >>>> >> >> > --- a/drivers/base/Kconfig >>>> >> >> > +++ b/drivers/base/Kconfig >>>> >> >> > @@ -144,15 +144,21 @@ config EXTRA_FIRMWARE_DIR >>>> >> >> > some other directory containing the firmware files. >>>> >> >> > >>>> >> >> > config FW_LOADER_USER_HELPER >>>> >> >> > + bool >>>> >> >> > + >>>> >> >> > +config FW_LOADER_USER_HELPER_FALLBACK >>>> >> >> > bool "Fallback user-helper invocation for firmware loading" >>>> >> >> > depends on FW_LOADER >>>> >> >> > - default y >>>> >> >> > + select FW_LOADER_USER_HELPER >>>> >> >> > help >>>> >> >> > This option enables / disables the invocation of >>>> >> >> > user-helper >>>> >> >> > (e.g. udev) for loading firmware files as a fallback >>>> >> >> > after the >>>> >> >> > direct file loading in kernel fails. The user-mode >>>> >> >> > helper is >>>> >> >> > no longer required unless you have a special firmware >>>> >> >> > file >>>> >> >> > that >>>> >> >> > - resides in a non-standard path. >>>> >> >> > + resides in a non-standard path. Moreover, the udev >>>> >> >> > support has >>>> >> >> > + been deprecated upstream. >>>> >> >> > + >>>> >> >> > + If you are unsure about this, say N here. >>>> >> >> >>>> >> >> It may be safer to say Y here for fallback if not sure. >>>> >> > >>>> >> > Saying Y here will be actively harmful if the firmware loader is >>>> >> > disabled in >>>> >> > udev (which I guess most distros will do as soon as they can), so I >>>> >> > think we >>>> >> >>>> >> If fallback is triggered, it means that the firmware can't be found >>>> >> in default direct rootfs path, so it is better to continue to look for >>>> >> it >>>> >> from userspace. >>>> >> >>>> >> Also it won't a big problem for hanging the request user context >>>> >> for some while(60sec at default) if udev is disabled, will it? >>>> >> >>>> >> BTW, are you sure most distros will do that in the near future? >>>> >> >>>> >> > should advice people to say N unless they really know what they are >>>> >> > doing >>>> >> > and that their userspace can cope with it. >>>> >> >>>> >> That is why I suggest to say Y if someone isn't sure. >>>> > >>>> > For the time being, having default this Y causes more troubles. >>>> >>>> I am wondering why default Y may cause more troubles, as we >>>> know, it has been default Y for long long time. >>> >>> More trouble = more bug reports. At least, a handful distros suffer. >>> I don't know the situation with Ubuntu, though. >> >> Looks recently not see related report, :-) > > Ubuntu currently enables the firmware loader in both the kernel and in > udev, so would not yet have a problem here at the moment. However, I > spoke with Martin Pitt and he told me that both Debian and Ubuntu > would like to switch this off in udev once it is possible (i.e., once > this patch has been merged I guess). Fedora already did, and speaking > for Arch we definitely would like to do the same. I did not check with > other distros, but I'm pretty sure "everyone" will disable this in > udev by the next cycle. At which point having it enabled in the kernel > will cause real problems and bug reports.
That won't cover the case of old distributions with new kernel, do you want to break/confuse these users? > > For distro kernels that's not a problem, as they know what to do, but > I guess for random kernel users we should give them the correct > recommendation. Also I remember that android users put firmware under their special path. > >>>> It only falls back if the request fw is _not_ found from direct loading, >>>> so it is reasonable to try to continue to look for it from user space. >> >>> Some drivers fall back to different firmware (e.g. different revision >>> suffix) if the requested file isn't found. So, this happens in >>> reality. >> >> So do you think the fallback is better or worse? For CPU microcode >> case, maybe it is fine, but for other devices, maybe it is better to >> get a firmware for working at least. > > What usecase do you have in mind here? For people using stock udev, > enabling the fallback will not give any benefit, but it will soon Again, we have old distributions, also it should make sense to fall back to userspace for non-exist firmwares under default path. > start giving real problems... If there isn't firmwares at default path for devices, the device may not work, and that is the real problem. Thanks, -- Ming Lei -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
