[PATCH AUTOSEL 6.6 11/18] ACPI: Add missing prototype for non CONFIG_SUSPEND/CONFIG_X86 case

[Sasha Levin <sashal@kernel.org>]

From: Mario Limonciello <mario.limonciello@amd.com>

[ Upstream commit e1bdbbc98279164d910d2de82a745f090a8b249f ]

acpi_register_lps0_dev() and acpi_unregister_lps0_dev() may be used
in drivers that don't require CONFIG_SUSPEND or compile on !X86.

Add prototypes for those cases.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202502191627.fRgoBwcZ-lkp@intel.com/
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Link: https://patch.msgid.link/20250407183656.1503446-1-superm1@kernel.org
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

**YES** This commit should be backported to stable kernel trees.
**Analysis:** This commit fixes a clear build error that affects users
in specific, but valid, kernel configurations. Here's the detailed
analysis: **1. Clear Bug Fix:** The commit addresses missing function
prototypes for `acpi_register_lps0_dev()` and
`acpi_unregister_lps0_dev()` when `CONFIG_SUSPEND` or `CONFIG_X86` are
not enabled. This causes compilation failures when drivers that use
these functions are built without these config options. **2. Code
Changes Analysis:** - **File Modified:** `include/linux/acpi.h` at lines
1108-1162 - **Before:** The `struct acpi_s2idle_dev_ops` was only
defined within the `#if defined(CONFIG_SUSPEND) && defined(CONFIG_X86)`
block, and the stub functions for `acpi_register_lps0_dev()` and
`acpi_unregister_lps0_dev()` were missing from the `#else` clause. -
**After:** The struct definition is moved outside the conditional block,
and stub functions are added in the `#else` clause that return `-ENODEV`
for registration and do nothing for unregistration. **3. Real-world
Impact:** From examining the kernel tree, several drivers use these
functions: - `/home/sasha/linux/drivers/platform/x86/amd/pmc/pmc.c` -
AMD PMC driver calls `acpi_register_lps0_dev()` and
`acpi_unregister_lps0_dev()` -
`/home/sasha/linux/arch/x86/platform/atom/punit_atom_debug.c` - Intel
Atom debug driver - `/home/sasha/linux/drivers/platform/x86/pmc_atom.c`
- Intel PMC Atom driver These drivers can be enabled on platforms or
configurations where `CONFIG_SUSPEND` or `CONFIG_X86` might not be set,
causing build failures. **4. Minimal Risk:** - **Size:** Very small
change - only adds stub function prototypes - **Scope:** Limited to
header file, no runtime behavior changes for existing working
configurations - **Side Effects:** None - the stubs return appropriate
error codes and maintain API compatibility **5. Comparison with Similar
Commits:** Looking at the provided similar commits, this follows the
same pattern as commits #2, #3, and #4 (all marked as NO), which were
prototype/warning fixes. However, this commit differs crucially because:
- It fixes actual **build failures** (not just warnings) - The kernel
test robot specifically reported compilation errors - It affects **real
drivers** that are in use **6. Stable Tree Criteria Compliance:** - ✅
Fixes important bugs (build failures) - ✅ Doesn't introduce new features
- ✅ Doesn't make architectural changes - ✅ Has minimal risk of
regression - ✅ Is confined to a specific subsystem (ACPI headers) The
commit message explicitly mentions "kernel test robot" reporting build
failures, indicating this is a real issue affecting automated testing
and potentially user builds. The fix is exactly what's needed for proper
API completeness - providing stub implementations when the real
functionality isn't available.

 include/linux/acpi.h | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 1b76d2f83eac6..7c6f4006389da 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -1098,13 +1098,13 @@ void acpi_os_set_prepare_extended_sleep(int (*func)(u8 sleep_state,
 
 acpi_status acpi_os_prepare_extended_sleep(u8 sleep_state,
 					   u32 val_a, u32 val_b);
-#if defined(CONFIG_SUSPEND) && defined(CONFIG_X86)
 struct acpi_s2idle_dev_ops {
 	struct list_head list_node;
 	void (*prepare)(void);
 	void (*check)(void);
 	void (*restore)(void);
 };
+#if defined(CONFIG_SUSPEND) && defined(CONFIG_X86)
 int acpi_register_lps0_dev(struct acpi_s2idle_dev_ops *arg);
 void acpi_unregister_lps0_dev(struct acpi_s2idle_dev_ops *arg);
 int acpi_get_lps0_constraint(struct acpi_device *adev);
@@ -1113,6 +1113,13 @@ static inline int acpi_get_lps0_constraint(struct device *dev)
 {
 	return ACPI_STATE_UNKNOWN;
 }
+static inline int acpi_register_lps0_dev(struct acpi_s2idle_dev_ops *arg)
+{
+	return -ENODEV;
+}
+static inline void acpi_unregister_lps0_dev(struct acpi_s2idle_dev_ops *arg)
+{
+}
 #endif /* CONFIG_SUSPEND && CONFIG_X86 */
 #ifndef CONFIG_IA64
 void arch_reserve_mem_area(acpi_physical_address addr, size_t size);
-- 
2.39.5