[PATCH v2 0/4] platform/x86: x86-android-tablets: use real firmware node references with intel drivers

[Bartosz Golaszewski]

First let me repeat the problem statement:

==

GPIO software node lookup should rely exclusively on matching the
addresses of the referenced firmware nodes. I tried to enforce it with
commit e5d527be7e69 ("gpio: swnode: don't use the swnode's name as the
key for GPIO lookup") but it broke existing users who abuse the software
node mechanism by creating "dummy" software nodes named after the device
they want to get GPIOs from but never attaching them to the actual GPIO
devices. They rely on the current behavior of GPIOLIB where it will match
the label of the GPIO controller against the name of the software node
and does not require a true link.

x86-android-tablets driver is one of the abusers in that it creates
dummy software nodes for baytrail and cherryview GPIO controllers but
they don't really reference these devices. Before we can reapply
e5d527be7e69 and support matching by fwnode address exclusively, we need
to convert all the users to using actual fwnode references.

==

Now for the new approach:

Now with the recent patches I sent or plan to send out, it turns out
that almost all existing users of software node lookup can easily have
the software node's representing the GPIO controllers attached to their
target devices as their primary firmware node. The remaining complex
cases are: pcengines-apuv2 and geode-common but in the first case we
have control over the creation of the GPIO device - we can assign it a
firmware node - and in the second case, we deal with an MFD driver so
can export the cell's software node in a header.

The only remaining use-case where we need to reference a GPIO controller
described in ACPI from a software node is the x86-android-tablets
driver. In this case, I think it no longer makes sense to propose a new
generic interface. Instead, I'd like to propose to keep it as a
driver-specific quirk.

This series proposes the following changes:
1. Switch to returning -ENXIO if we try to resolve a reference to
a software node that's not registered as a firmware node yet to
differentiate it from other situations in which we return -ENOENT.
2. In GPIO core: return -EPROBE_DEFER from swnode lookup if
fwnode_get_reference_args() returns -ENXIO as an unregistered software
node is not much different from the situation where there's a firmware
node not backed by a device yet.
3. Export the acpi_bus_type symbol. It's already available in the
acpi_bus.h header but it's not available to loadable modules.
4. Finally: implement support for dynamic assignment of secondary
firmware nodes in the x86-android-tablets driver. More details on how
it's approached are in the relevant commit message.

Merging strategy: I'd like to propose queing patches 1-3 independently
through their respective trees: driver core, GPIO and ACPI. The final
patch would make its way upstream after v7.1-rc1. I would probably
extend it to convert the driver to using more devres interfaces too at
this point.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>
---
Changes in v2:
- Completely new approach
- Keep the cherryview and baytrail secondary fwnode handling as a
  driver-specific quirk for x86 tablets and don't introduce any new API
- Change the return value when resolving a reference to an unregistered
  software node and defer probe in GPIOLIB in that situation
- Export acpi_bus_type for use in x86-android-tablets
- Link to v1: https://patch.msgid.link/20260319-baytrail-real-swnode-v1-0-75f2264ae49f@xxxxxxxxxxxxxxxx

---
Bartosz Golaszewski (4):
      software node: return -ENXIO when referenced swnode is not registered yet
      gpio: swnode: defer probe on references to unregistered software nodes
      ACPI: bus: export the acpi_bus_type symbol
      platform/x86: x86-android-tablets: enable fwnode matching of GPIO chips

 drivers/acpi/bus.c                              |   1 +
 drivers/base/swnode.c                           |   2 +-
 drivers/gpio/gpiolib-swnode.c                   |   9 ++
 drivers/platform/x86/x86-android-tablets/core.c | 127 +++++++++++++++++++++++-
 4 files changed, 135 insertions(+), 4 deletions(-)
---
base-commit: d18fd67e5f09e800611b02e2afda430a870a136b
change-id: 20260319-baytrail-real-swnode-7de7a3870f78

Best regards,
-- 
Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>