linux-kernel - [PATCH 07/13] eeepc-laptop: make disp attribute really write-only

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Date:	Sat, 13 Sep 2014 01:06:46 +0200
From:	Frans Klaver <fransklaver@...il.com>
To:	Darren Hart <dvhart@...radead.org>
Cc:	Frans Klaver <fransklaver@...il.com>,
	Corentin Chary <corentin.chary@...il.com>,
	Rafael Wysocki <rafael.j.wysocki@...el.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	acpi4asus-user@...ts.sourceforge.net,
	platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 07/13] eeepc-laptop: make disp attribute really write-only

The disp attribute is write-only, but sysfs doesn't know this. Currently
show_sys_acpi() is mimicking sysfs behavior, if the underlying acpi call
should fail. This is not ideal; behaving like sysfs is better left to
sysfs.

Introduce EEEPC_CREATE_DEVICE_ATTR_WO() to instantiate a write-only
attribute, and declare the disp attribute with it. Sysfs makes sure
userspace can only write to disp at all times. This also means we can
back to propagating any errors from get_acpi().

Signed-off-by: Frans Klaver <fransklaver@...il.com>
---
 drivers/platform/x86/eeepc-laptop.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/platform/x86/eeepc-laptop.c b/drivers/platform/x86/eeepc-laptop.c
index 3c04b77..4f6490d 100644
--- a/drivers/platform/x86/eeepc-laptop.c
+++ b/drivers/platform/x86/eeepc-laptop.c
@@ -291,7 +291,7 @@ static ssize_t show_sys_acpi(struct device *dev, int cm, char *buf)
 	int value = get_acpi(eeepc, cm);
 
 	if (value < 0)
-		return -EIO;
+		return value;
 	return sprintf(buf, "%d\n", value);
 }
 
@@ -316,9 +316,13 @@ static ssize_t show_sys_acpi(struct device *dev, int cm, char *buf)
 	EEEPC_ACPI_STORE_FUNC(_name, _cm)				\
 	static DEVICE_ATTR(_name, _mode, show_##_name, store_##_name)
 
+#define EEEPC_CREATE_DEVICE_ATTR_WO(_name, _mode, _cm)			\
+	EEEPC_ACPI_STORE_FUNC(_name, _cm)				\
+	static DEVICE_ATTR(_name, _mode, NULL, store_##_name)
+
 EEEPC_CREATE_DEVICE_ATTR(camera, S_IWUSR | S_IRUGO, CM_ASL_CAMERA);
 EEEPC_CREATE_DEVICE_ATTR(cardr, S_IWUSR | S_IRUGO, CM_ASL_CARDREADER);
-EEEPC_CREATE_DEVICE_ATTR(disp, S_IWUSR, CM_ASL_DISPLAYSWITCH);
+EEEPC_CREATE_DEVICE_ATTR_WO(disp, S_IWUSR, CM_ASL_DISPLAYSWITCH);
 
 struct eeepc_cpufv {
 	int num;
-- 
2.1.0

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