Re: [PATCH 5.10 290/491] ACPI: EC: Install address space handler at the namespace root

Ben Hutchings
2026-04-13T20:53:41Z

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On Mon, 2026-04-13 at 17:58 +0200, Greg Kroah-Hartman wrote:
> 5.10-stable review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> [ Upstream commit 60fa6ae6e6d09e377fce6f8d9b6f6a4d88769f63 ]

It appears that this can cause regressions, which were fixed by commits
71bf41b8e913 ("ACPI: EC: Evaluate _REG outside the EC scope more
carefully") and 0e6b6dedf168 ("ACPI: EC: Evaluate orphan _REG under EC
device") upstream. I didn't check whether those would apply and build
cleanly here, but if not then this may have to be dropped.

Ben.

> It is reported that _DSM evaluation fails in ucsi_acpi_dsm() on Lenovo
> IdeaPad Pro 5 due to a missing address space handler for the EC address
> space:
>
> ACPI Error: No handler for Region [ECSI] (000000007b8176ee) [EmbeddedControl] (20230628/evregion-130)
>
> This happens because if there is no ECDT, the EC driver only registers
> the EC address space handler for operation regions defined in the EC
> device scope of the ACPI namespace while the operation region being
> accessed by the _DSM in question is located beyond that scope.
>
> To address this, modify the ACPI EC driver to install the EC address
> space handler at the root of the ACPI namespace for the first EC that
> can be found regardless of whether or not an ECDT is present.
>
> Note that this change is consistent with some examples in the ACPI
> specification in which EC operation regions located outside the EC
> device scope are used (for example, see Section 9.17.15 in ACPI 6.5),
> so the current behavior of the EC driver is arguably questionable.
>
> Reported-by: webcaptcha <webcapcha@gmail.com>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=218789
> Link: https://uefi.org/specs/ACPI/6.5/09_ACPI_Defined_Devices_and_Device_Specific_Objects.html#example-asl-code
> Link: https://lore.kernel.org/linux-acpi/Zi+0whTvDbAdveHq@kuha.fi.intel.com
> Suggested-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Reviewed-by: Hans de Goede <hdegoede@redhat.com>
> Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Stable-dep-of: f6484cadbcaf ("ACPI: EC: clean up handlers on probe failure in acpi_ec_setup()")
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
> drivers/acpi/ec.c | 25 ++++++++++++++++---------
> drivers/acpi/internal.h | 1 -
> 2 files changed, 16 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
> index 10f7e3ef58791..1d7e7e47ea0e4 100644
> --- a/drivers/acpi/ec.c
> +++ b/drivers/acpi/ec.c
> @@ -1514,13 +1514,14 @@ static bool install_gpio_irq_event_handler(struct acpi_ec *ec)
> static int ec_install_handlers(struct acpi_ec *ec, struct acpi_device *device,
> bool call_reg)
> {
> + acpi_handle scope_handle = ec == first_ec ? ACPI_ROOT_OBJECT : ec->handle;
> acpi_status status;
>
> acpi_ec_start(ec, false);
>
> if (!test_bit(EC_FLAGS_EC_HANDLER_INSTALLED, &ec->flags)) {
> acpi_ec_enter_noirq(ec);
> - status = acpi_install_address_space_handler_no_reg(ec->handle,
> + status = acpi_install_address_space_handler_no_reg(scope_handle,
> ACPI_ADR_SPACE_EC,
> &acpi_ec_space_handler,
> NULL, ec);
> @@ -1529,11 +1530,10 @@ static int ec_install_handlers(struct acpi_ec *ec, struct acpi_device *device,
> return -ENODEV;
> }
> set_bit(EC_FLAGS_EC_HANDLER_INSTALLED, &ec->flags);
> - ec->address_space_handler_holder = ec->handle;
> }
>
> if (call_reg && !test_bit(EC_FLAGS_EC_REG_CALLED, &ec->flags)) {
> - acpi_execute_reg_methods(ec->handle, ACPI_ADR_SPACE_EC);
> + acpi_execute_reg_methods(scope_handle, ACPI_ADR_SPACE_EC);
> set_bit(EC_FLAGS_EC_REG_CALLED, &ec->flags);
> }
>
> @@ -1585,10 +1585,13 @@ static int ec_install_handlers(struct acpi_ec *ec, struct acpi_device *device,
>
> static void ec_remove_handlers(struct acpi_ec *ec)
> {
> + acpi_handle scope_handle = ec == first_ec ? ACPI_ROOT_OBJECT : ec->handle;
> +
> if (test_bit(EC_FLAGS_EC_HANDLER_INSTALLED, &ec->flags)) {
> if (ACPI_FAILURE(acpi_remove_address_space_handler(
> - ec->address_space_handler_holder,
> - ACPI_ADR_SPACE_EC, &acpi_ec_space_handler)))
> + scope_handle,
> + ACPI_ADR_SPACE_EC,
> + &acpi_ec_space_handler)))
> pr_err("failed to remove space handler\n");
> clear_bit(EC_FLAGS_EC_HANDLER_INSTALLED, &ec->flags);
> }
> @@ -1627,14 +1630,18 @@ static int acpi_ec_setup(struct acpi_ec *ec, struct acpi_device *device, bool ca
> {
> int ret;
>
> - ret = ec_install_handlers(ec, device, call_reg);
> - if (ret)
> - return ret;
> -
> /* First EC capable of handling transactions */
> if (!first_ec)
> first_ec = ec;
>
> + ret = ec_install_handlers(ec, device, call_reg);
> + if (ret) {
> + if (ec == first_ec)
> + first_ec = NULL;
> +
> + return ret;
> + }
> +
> pr_info("EC_CMD/EC_SC=0x%lx, EC_DATA=0x%lx\n", ec->command_addr,
> ec->data_addr);
>
> diff --git a/drivers/acpi/internal.h b/drivers/acpi/internal.h
> index 4edf591f8a3a5..f6c929787c9e6 100644
> --- a/drivers/acpi/internal.h
> +++ b/drivers/acpi/internal.h
> @@ -169,7 +169,6 @@ static inline void acpi_early_processor_osc(void) {}
> -------------------------------------------------------------------------- */
> struct acpi_ec {
> acpi_handle handle;
> - acpi_handle address_space_handler_holder;
> int gpe;
> int irq;
> unsigned long command_addr;

--
Ben Hutchings
When in doubt, use brute force. - Ken Thompson

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