linux-kernel - Re: [PATCH 1/2] acpi: Add acpi_init

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Date:   Wed, 28 Jul 2021 09:57:13 -0700
From:   "David E. Box" <david.e.box@...ux.intel.com>
To:     Hans de Goede <hdegoede@...hat.com>,
        Michael Bottini <michael.a.bottini@...ux.intel.com>,
        rjw@...ysocki.net, lenb@...nel.org, irenic.rajneesh@...il.com,
        mgross@...ux.intel.com
Cc:     linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        platform-driver-x86@...r.kernel.org
Subject: Re: [PATCH 1/2] acpi: Add acpi_init_properties to ACPI driver code

On Wed, 2021-07-28 at 11:10 +0200, Hans de Goede wrote:
> Hi,
> 
> On 7/28/21 11:08 AM, Hans de Goede wrote:
> > Hi,
> > 
> > On 7/23/21 10:21 PM, Michael Bottini wrote:
> > > Some products in the field, like Intel Rocket Lake systems,
> > > contain
> > > AML code that can modify _DSD properties after they have been
> > > evaluated by ACPI init code. Therefore, there is a need for
> > > drivers
> > > to be able to reevaluate _DSDs so that the updated property
> > > values can
> > > be read. Export acpi_init_properties() for this purpose.
> > > 
> > > Signed-off-by: Michael Bottini
> > > <michael.a.bottini@...ux.intel.com>
> > 
> > My first instinct here is this is a firmware bug and we should
> > go out of our way here to not support this and to instead apply
> > pressure on the vendor to get the firmware fixed.
> > 
> > Let me explain, the standard use of _DSD is to allow embedding
> > open-firmware/devicetree style properties inside ACPI nodes.
> > 
> > devicetree files, unlike AML contain static information, which
> > is parsed once and only once.
> > 
> > Allowing AML code to dynamically change _DSD results pretty
> > much breaks this entire model.
> > 
> > So I might be shooting from the hip a bit here:
> > "no, just no". IOW nack.
> 
> I should have read the rest of the thread first I guess.
> 
> I see that Andy and Rafael are saying the same thing.
> 
> So here we have 3 people who all 3 are somewhat experts in ACPI
> saying no to this. So yes please talk to the BIOS team as you
> indicated elsewhere in the thread.
> 
> Regards,
> 
> Hans

We get that reevaluating the _DSD would be against spec. We have taken
this back to the firmware team as a bug and asked for a fix or
different solution. Thanks.

> 
> 
> 
> 
> > > ---
> > >  drivers/acpi/property.c | 1 +
> > >  include/linux/acpi.h    | 6 ++++++
> > >  2 files changed, 7 insertions(+)
> > > 
> > > diff --git a/drivers/acpi/property.c b/drivers/acpi/property.c
> > > index e312ebaed8db..2c1f8cf1a8f0 100644
> > > --- a/drivers/acpi/property.c
> > > +++ b/drivers/acpi/property.c
> > > @@ -432,6 +432,7 @@ void acpi_init_properties(struct acpi_device
> > > *adev)
> > >         if (!adev->data.pointer)
> > >                 acpi_extract_apple_properties(adev);
> > >  }
> > > +EXPORT_SYMBOL(acpi_init_properties);
> > >  
> > >  static void acpi_destroy_nondev_subnodes(struct list_head *list)
> > >  {
> > > diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> > > index 72e4f7fd268c..57defc3bc9b9 100644
> > > --- a/include/linux/acpi.h
> > > +++ b/include/linux/acpi.h
> > > @@ -716,6 +716,8 @@ static inline u64
> > > acpi_arch_get_root_pointer(void)
> > >  
> > >  int acpi_get_local_address(acpi_handle handle, u32 *addr);
> > >  
> > > +void acpi_init_properties(struct acpi_device *adev);
> > > +
> > >  #else  /* !CONFIG_ACPI */
> > >  
> > >  #define acpi_disabled 1
> > > @@ -976,6 +978,10 @@ static inline int
> > > acpi_get_local_address(acpi_handle handle, u32 *addr)
> > >         return -ENODEV;
> > >  }
> > >  
> > > +static inline void acpi_init_properties(struct acpi_device
> > > *adev)
> > > +{
> > > +}
> > > +
> > >  #endif /* !CONFIG_ACPI */
> > >  
> > >  #ifdef CONFIG_ACPI_HOTPLUG_IOAPIC
> > > 
>