On Mon, Feb 1, 2021 at 5:35 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
>
> With the new 2 step scanning process, which defers instantiating some
> ACPI-devices based on their _DEP to the second step, the following may
> happen:
>
> 1. During the first acpi_walk_namespace(acpi_bus_check_add) call
> acpi_scan_check_dep() gets called on the Battery ACPI dev handle and
> adds one or more deps for this handle to the acpi_dep_list
>
> 2. During the first acpi_bus_attach() call one or more of the suppliers of
> these deps get their driver attached and
> acpi_walk_dep_device_list(supplier_handle) gets called.
>
> At this point acpi_bus_get_device(dep->consumer) get called,
> but since the battery has DEPs it has not been instantiated during the
> first acpi_walk_namespace(acpi_bus_check_add), so the
> acpi_bus_get_device(dep->consumer) call fails.
>
> Before this commit, acpi_walk_dep_device_list() would now continue
> *without* removing the acpi_dep_data entry for this supplier,consumer
> pair from the acpi_dep_list.
Yeah, I've overlooked the fact that the consumer needs to have a
struct acpi_device in order for the entry to be dropped from the list.
Sorry.
> 3. During the second acpi_walk_namespace(acpi_bus_check_add) call
> an acpi_device gets instantiated for the battery and
> acpi_scan_dep_init() gets called to initialize its dep_unmet val.
>
> Before this commit, the dep_unmet count would include DEPs for
> suppliers for which acpi_walk_dep_device_list(supplier_handle)
> has already been called, so it will never become 0 and the
> ACPI battery driver will never get attached / bind.
>
> Fix the ACPI battery driver never binding in this scenario by making
> acpi_walk_dep_device_list() always remove matching acpi_dep_data
> entries independent of the acpi_bus_get_device(dep->consumer) call
> succeeding or not.
>
> Fixes: 71da201f38df ("ACPI: scan: Defer enumeration of devices with _DEP lists")
> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
Applied and thanks for fixing this!
> ---
> drivers/acpi/scan.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index 5d7b2fcecf06..4ce54115e981 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -2123,12 +2123,12 @@ void acpi_walk_dep_device_list(acpi_handle handle)
> list_for_each_entry_safe(dep, tmp, &acpi_dep_list, node) {
> if (dep->supplier == handle) {
> acpi_bus_get_device(dep->consumer, &adev);
> - if (!adev)
> - continue;
>
> - adev->dep_unmet--;
> - if (!adev->dep_unmet)
> - acpi_bus_attach(adev, true);
> + if (adev) {
> + adev->dep_unmet--;
> + if (!adev->dep_unmet)
> + acpi_bus_attach(adev, true);
> + }
>
> list_del(&dep->node);
> kfree(dep);
> --
> 2.29.2
>
