Re: [PATCH v3 3/3] platform/x86: dell-smbios: Link all dell-smbios-* modules together

[Darren Hart <dvhart@infradead.org>]

On Sat, Mar 03, 2018 at 11:59:55AM +0000, Mario.Limonciello@dell.com wrote:
> > -----Original Message-----
> > From: Darren Hart [mailto:dvhart@infradead.org]
> > Sent: Friday, March 2, 2018 8:11 PM
> > To: Limonciello, Mario <Mario_Limonciello@Dell.com>
> > Cc: Andy Shevchenko <andy.shevchenko@gmail.com>; pali.rohar@gmail.com; LKML
> > <linux-kernel@vger.kernel.org>; platform-driver-x86@vger.kernel.org
> > Subject: Re: [PATCH v3 3/3] platform/x86: dell-smbios: Link all dell-smbios-*
> > modules together
> > 
> > On Tue, Feb 27, 2018 at 12:23:04PM -0600, Mario Limonciello wrote:
> > > Some race conditions were raised due to dell-smbios and its backends
> > > not being ready by the time that a consumer would call one of the
> > > exported methods.
> > >
> > > To avoid this problem, guarantee that all initialization has been
> > > done by linking them all together and running init for them all.
> > >
> > > As part of this change the Kconfig needs to be adjusted so that
> > > CONFIG_DELL_SMBIOS_SMM and CONFIG_DELL_SMBIOS_WMI are boolean
> > > rather than modules.
> > >
> > > CONFIG_DELL_SMBIOS is a visually selectable option again and both
> > > CONFIG_DELL_SMBIOS_WMI and CONFIG_DELL_SMBIOS_SMM are optional.
> > >
> > > Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
> > > ---
> > > Changes from v2:
> > >  * Move rest of #ifdef out of source files
> > >  * Only compile units as necessary
> > >
> > >  drivers/platform/x86/Kconfig            | 11 ++++++++---
> > >  drivers/platform/x86/Makefile           |  4 ++--
> > >  drivers/platform/x86/dell-smbios-base.c | 21 ++++++++++++++++++++-
> > >  drivers/platform/x86/dell-smbios-smm.c  | 18 ++++--------------
> > >  drivers/platform/x86/dell-smbios-wmi.c  | 14 ++++----------
> > >  drivers/platform/x86/dell-smbios.h      | 27 ++++++++++++++++++++++++++-
> > >  6 files changed, 64 insertions(+), 31 deletions(-)
> > >
> > > diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
> > > index 9a8f964..0c0897e 100644
> > > --- a/drivers/platform/x86/Kconfig
> > > +++ b/drivers/platform/x86/Kconfig
> > > @@ -106,10 +106,15 @@ config ASUS_LAPTOP
> > >  	  If you have an ACPI-compatible ASUS laptop, say Y or M here.
> > >
> > >  config DELL_SMBIOS
> > > -	tristate
> > > +	tristate "Dell SMBIOS driver"
> > > +	---help---
> > > +	This provides support for the Dell SMBIOS calling interface.
> > > +	If you have a Dell computer you should enable this option.
> > > +
> > > +	Be sure to select at least one backend for it to work properly.
> > >
> > >  config DELL_SMBIOS_WMI
> > > -	tristate "Dell SMBIOS calling interface (WMI implementation)"
> > > +	bool "Dell SMBIOS driver WMI support"
> > >  	depends on ACPI_WMI
> > >  	select DELL_WMI_DESCRIPTOR
> > >  	select DELL_SMBIOS
> > 
> > Blarg, this also violates the kconfig-language guidance for using select
> > only for non-visible symbols with no dependencies.
> > 
> > I have a patch that works, but I don't love it. We can remove the prompt
> > from DELL_SMBIOS, and make DELL_SMBIOS_WMI|SMM "depend on"
> > DELL_SMBIOS.
> > The options just appear sort of randomly when either DELL_LAPTOP or
> > DELL_WMI are selected - but they can default to y, which is nice.
> > 
> > I have a subsequent patch which makes DELL_SMBIOS_WMI|SMM "depend on"
> > DELL_LAPTOP, which makes this look a lot nicer. These just appear under
> > DELL_LAPTOP as bool options. The problem with this approach is DELL_WMI
> > also requires DELL_SMBIOS and DELL_WMI doesn't currently depend on
> > DELL_LAPTOP. One option is to make it depend on DELL_LAPTOP as it seems
> > unlikely for them to ever be used separately.  I don't love this either.
> > Thoughts?
> > 
> > Perhaps the compromise is leave the DELL_SMBIOS prompt. This doesn't
> > have the negative consequences the kconfig-languages is trying to guard
> > against, and it makes it obvious what the DELL_SMBIOS_* options are -
> > and we can still default them to y. See below.
> > 
> > This seems like it might be the least bad option at the moment. I'll
> > keep thinking on it a bit...
> > 
> > From: "Darren Hart (VMware)" <dvhart@infradead.org>
> > Date: Fri, 2 Mar 2018 17:40:32 -0800
> > Subject: [PATCH] platform/x86: Allow for SMBIOS backend defaults
> > 
> > Avoid accidental configurations by setting default y for DELL_SMBIOS
> > backends. Avoid this impacting the default build size, by making them
> > dependent on DELL_SMBIOS, so they only appear when DELL_SMBIOS is
> > manually selected, or by DELL_LAPTOP or DELL_WMI.
> > 
> > Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>
> > ---
> >  drivers/platform/x86/Kconfig | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
> > index e3f682c..022c837 100644
> > --- a/drivers/platform/x86/Kconfig
> > +++ b/drivers/platform/x86/Kconfig
> > @@ -115,9 +115,10 @@ config DELL_SMBIOS
> > 
> >  config DELL_SMBIOS_WMI
> >  	bool "Dell SMBIOS driver WMI backend"
> > +	default y
> >  	depends on ACPI_WMI
> >  	select DELL_WMI_DESCRIPTOR
> > -	select DELL_SMBIOS
> > +	depends on DELL_SMBIOS
> >  	---help---
> >  	This provides an implementation for the Dell SMBIOS calling interface
> >  	communicated over ACPI-WMI.
> > @@ -128,8 +129,9 @@ config DELL_SMBIOS_WMI
> > 
> >  config DELL_SMBIOS_SMM
> >  	bool "Dell SMBIOS driver SMM backend"
> > +	default y
> >  	depends on DCDBAS
> > -	select DELL_SMBIOS
> > +	depends on DELL_SMBIOS
> >  	---help---
> >  	This provides an implementation for the Dell SMBIOS calling interface
> >  	communicated over SMI/SMM.
> > --
> > 2.9.5
> > 
> > 
> 
> Ooph. I think the compromise of leaving the dell smbios prompt and sane defaults
> behind extras is the best.
> With it being a library now there shouldn't be a way for someone to break other
> modules in unexpected ways.  Init will fail for dell-smbios and then nothing
> else will be able to use it.
> 

OK, I'm going to go with the above patch with a little more context about the
visible and selectable DELL_SMBIOS. We can revisit if all this belongs under a
DELL_EXTRAS menuconfig as a separate exercise.

I am planning on pushing your 3 and my patch above to the 4.16 rc cycle. Holler
if that wasn't your expectation.

-- 
Darren Hart
VMware Open Source Technology Center