Hi,
> -----Original Message-----
> From: Hans de Goede <hdegoede@xxxxxxxxxx>
> Sent: Tuesday, March 30, 2021 1:24 PM
> To: Ksr, Prasanth; Mark Gross; Andy Shevchenko
> Cc: Limonciello, Mario; Bharathi, Divya; Alexander Naumann; platform-driver-
> x86@xxxxxxxxxxxxxxx; Yuan, Perry
> Subject: Re: [PATCH v2] platform/x86: dell-wmi-sysman: Make
> init_bios_attributes() ACPI object parsing more robust
>
>
> [EXTERNAL EMAIL]
>
> Hi,
>
> On 3/29/21 6:00 PM, Ksr, Prasanth wrote:
> > Hi,
> >
> >> -----Original Message-----
> >> From: Hans de Goede <hdegoede@xxxxxxxxxx>
> >> Sent: Friday, March 26, 2021 10:14 PM
> >> To: Ksr, Prasanth; Mark Gross; Andy Shevchenko
> >> Cc: Limonciello, Mario; Bharathi, Divya; Alexander Naumann;
> >> platform-driver- x86@xxxxxxxxxxxxxxx; Yuan, Perry
> >> Subject: Re: [PATCH v2] platform/x86: dell-wmi-sysman: Make
> >> init_bios_attributes() ACPI object parsing more robust
> >>
> >>
> >> [EXTERNAL EMAIL]
> >>
> >> Hi,
> >>
> >> On 3/26/21 4:40 PM, Ksr, Prasanth wrote:
> >>>
> >>>
> >>> Hi,
> >>>
> >>> [EXTERNAL EMAIL]
> >>>
> >>>> Hi,
> >>>>
> >>>> On 3/21/21 1:16 PM, Hans de Goede wrote:
> >>>>> Make init_bios_attributes() ACPI object parsing more robust:
> >>>>> 1. Always check that the type of the return ACPI object is
> >>>>> package,
> >> rather
> >>>>> then only checking this for instance_id == 0 2. Check that the
> >>>>> package has the minimum amount of elements which will
> >>>>> be consumed by the populate_foo_data() for the attr_type
> >>>>>
> >>>>> Note/TODO: The populate_foo_data() functions should also be made
> >>>>> more robust. The should check the type of each of the elements
> >>>>> matches the type which they expect and in case of
> >>>>> populate_enum_data()
> >>>>> obj->package.count should be passed to it as an argument and it
> >>>>> obj->should
> >>>>> re-check this itself since it consume a variable number of elements.
> >>>>>
> >>>>> Fixes: e8a60aa7404b ("platform/x86: Introduce support for Systems
> >>>>> Management Driver over WMI for Dell Systems")
> >>>>> Cc: Divya Bharathi <Divya_Bharathi@xxxxxxxx>
> >>>>> Cc: Mario Limonciello <mario.limonciello@xxxxxxxx>
> >>>>> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> >>>>> ---
> >>>>> Changes in v2:
> >>>>> - Restore behavior of returning -ENODEV when the
> >> get_wmiobj_pointer() call
> >>>>> for instance_id == 0 returns NULL. Otherwise
> >>>>> /sys/class/firmware-attributes/dell-wmi-sysman will get created
> >>>>> with
> >> an
> >>>>> empty attributes dir (empty except for pending_reboot and
> >>>>> reset_bios)
> >>>
> >>>> So the reason for this change in v2 is that testing on a Dell Latitude
> E5570:
> >>>> https://bugzilla.redhat.com/show_bug.cgi?id=1936171
> >>>>
> >>>> With v1 of this patch results in an empty attributes dir (empty
> >>>> except for
> >> pending_reboot and reset_bios), interestingly enough there are both
> >> System and Admin dirs created under Authentication, so the BIOS of
> >> this device seems to have the GUIDs for both the attributes and the
> >> authentication interfaces; and it >has the 2 standard authentication
> >> objects, theoretically allowing changing the BIOS passwords from
> >> within Linux, but it does not advertise any attributes which can be
> changed.
> >>>>
> >>>> With the new v2 patch, the driver will now simply refuse to load
> >>>> (and it
> >> should no longer crash during cleanup because of the other patches).
> >>>>
> >>>> But I wonder what is actually the right thing to do here ?
> >>>> Arguably being
> >> able to change the BIOS passwords has some value on its own ?
> >>>>
> >>>> Mario, what is your take on this?
> >>>
> >>> Ideally we should not be hitting this code path at all. I am working
> >>> with
> >> perry to see the results after applying the patches on the system.
> >>> If this is behavior we consistently see on older system BIOS then we
> >>> will
> >> patch the code to avoid code path and bail out early not loading the
> driver.
> >>
> >> With v2 of my patches (which have been merged) we do bail out as soon
> >> as it is clear that there is no enum-type (*) attribute with
> >> instance_id 0. That is pretty-much the earliest that we can bail and that
> works fine.
> >>
> >> What I was wondering is if that is the right thing to do though. On
> >> the E5570 there seem to be no enum/int/str attributes at all but what
> >> if there are enum
> >> + int attributes + no str attributes for example ?
> >>
> > It would be right thing to do because this scenario happens because of
> some BIOS issue.
>
> Right, this is the right thing to do on machines such as the Latitude E5570.
>
> My question is more, what if, in the future some machine does not have say
> string bios-attributes, but it does have enum and int attributes ?
>
> The current code will then still refuse to bind / load, which seems wrong.
>
> Note that on the E5570 there are no enum and no string and no int
> attributes, so we could also delay the return -ENODEV until after we have
> enumerated all 3 types and if all 3 have a wmi_priv.foo_instances_count of 0
> then return -ENODEV that seems like the logical thing to do here to me.
It is not only with Latitude E5570 and this device is an example of one such case which we are mentioning
We expect all 3 categories to be present always for supported platforms. Even a system with minimal BIOS attributes will have at least few mandatory attributes in each of the three categories.
If BIOS don't have any one category GUID exposed then it will be faulty BIOS and our driver must refuse to bind/load. Hence, we believe that current code has right logic.
