linux-kernel - [PATCH AUTOSEL for 4.4 07/35] ACPI / bus: Leave modalias empty for devices which are not present

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Message-ID: <20180124041645.32420-7-alexander.levin@microsoft.com>
Date:   Wed, 24 Jan 2018 04:16:55 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
CC:     Hans de Goede <hdegoede@...hat.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL for 4.4 07/35] ACPI / bus: Leave modalias empty for
 devices which are not present

From: Hans de Goede <hdegoede@...hat.com>

[ Upstream commit 10809bb976648ac58194a629e3d7af99e7400297 ]

Most Bay and Cherry Trail devices use a generic DSDT with all possible
peripheral devices present in the DSDT, with their _STA returning 0x00 or
0x0f based on AML variables which describe what is actually present on
the board.

Since ACPI device objects with a 0x00 status (not present) still get an
entry under /sys/bus/acpi/devices, and those entry had an acpi:PNPID
modalias, userspace would end up loading modules for non present hardware.

This commit fixes this by leaving the modalias empty for non present
devices. This results in 10 modules less being loaded with a generic
distro kernel config on my Cherry Trail test-device (a GPD pocket).

Signed-off-by: Hans de Goede <hdegoede@...hat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 drivers/acpi/device_sysfs.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/acpi/device_sysfs.c b/drivers/acpi/device_sysfs.c
index b9afb47db7ed..1521d9a41d25 100644
--- a/drivers/acpi/device_sysfs.c
+++ b/drivers/acpi/device_sysfs.c
@@ -146,6 +146,10 @@ static int create_pnp_modalias(struct acpi_device *acpi_dev, char *modalias,
 	int count;
 	struct acpi_hardware_id *id;
 
+	/* Avoid unnecessarily loading modules for non present devices. */
+	if (!acpi_device_is_present(acpi_dev))
+		return 0;
+
 	/*
 	 * Since we skip ACPI_DT_NAMESPACE_HID from the modalias below, 0 should
 	 * be returned if ACPI_DT_NAMESPACE_HID is the only ACPI/PNP ID in the
-- 
2.11.0