linux-kernel - [PATCH] ACPI / sysfs: Restructure get

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Date:   Thu,  7 Mar 2019 10:38:02 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>
Cc:     linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>
Subject: [PATCH] ACPI / sysfs: Restructure get_status

When building with -Wsometimes-uninitialized, Clang warns:

drivers/acpi/sysfs.c:667:13: warning: variable 'result' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]

Clang can't determine that all cases are covered by the two separate if
statements. We could combine then to look like this:

    int result;

    if (...) {
        ...
    } else if {
        ...
    } else {
        result -EINVAL;
    }

    return result;

However, at that point, we can further simplify this function by only
using result when absolutely needed and just direct returning the value
of the function.

Link: https://github.com/ClangBuiltLinux/linux/issues/388
Suggested-by: Nick Desaulniers <ndesaulniers@...gle.com>
Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
---
 drivers/acpi/sysfs.c | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/drivers/acpi/sysfs.c b/drivers/acpi/sysfs.c
index 41324f0b1bee..6ed785cadad9 100644
--- a/drivers/acpi/sysfs.c
+++ b/drivers/acpi/sysfs.c
@@ -651,23 +651,18 @@ static void acpi_global_event_handler(u32 event_type, acpi_handle device,
 static int get_status(u32 index, acpi_event_status *status,
 		      acpi_handle *handle)
 {
-	int result;
-
-	if (index >= num_gpes + ACPI_NUM_FIXED_EVENTS)
-		return -EINVAL;
-
 	if (index < num_gpes) {
-		result = acpi_get_gpe_device(index, handle);
+		int result = acpi_get_gpe_device(index, handle);
 		if (result) {
 			ACPI_EXCEPTION((AE_INFO, AE_NOT_FOUND,
 					"Invalid GPE 0x%x", index));
 			return result;
 		}
-		result = acpi_get_gpe_status(*handle, index, status);
+		return acpi_get_gpe_status(*handle, index, status);
 	} else if (index < (num_gpes + ACPI_NUM_FIXED_EVENTS))
-		result = acpi_get_event_status(index - num_gpes, status);
+		return acpi_get_event_status(index - num_gpes, status);
 
-	return result;
+	return -EINVAL;
 }
 
 static ssize_t counter_show(struct kobject *kobj,
-- 
2.21.0