linux-kernel - [PATCH 5/9] eeepc-laptop: tell sysfs that the disp attribute is write-only

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Date:	Wed, 17 Sep 2014 23:47:23 +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 5/9] eeepc-laptop: tell sysfs that the disp attribute is 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 was introduced in 6dff29b63a5bf2eaf3 "eeepc-laptop:
disp attribute should be write-only". 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 removes the need for
mimicking the sysfs behavior in show_sys_acpi() and store_sys_acpi(),
but we'll stick with -EIO, as changing sysfs return values should not be
taken lightly.

This change also causes EEEPC_CREATE_DEVICE_ATTR() to be used only for
R/W attributes. This enables us to drop the _mode argument from the
macro and use DEVICE_ATTR_RW() internally while we're at it. Append _RW
to the name for readability.

Signed-off-by: Frans Klaver <fransklaver@...il.com>
---
Here we're sticking with -EIO as return values. It should be said that the
commit mentioned above did change the error value from -ENODEV to -EIO. I'm
still in two minds about whether the show_sys_acpi and store_sys_acpi should go
back to returning ENODEV. We'll probably stick with -EIO, though, as there is
no strong reason other than "it was like that before".

 drivers/platform/x86/eeepc-laptop.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/platform/x86/eeepc-laptop.c b/drivers/platform/x86/eeepc-laptop.c
index c6d765f..a85da4f 100644
--- a/drivers/platform/x86/eeepc-laptop.c
+++ b/drivers/platform/x86/eeepc-laptop.c
@@ -311,14 +311,18 @@ static ssize_t show_sys_acpi(struct device *dev, int cm, char *buf)
 		return store_sys_acpi(dev, _cm, buf, count);		\
 	}
 
-#define EEEPC_CREATE_DEVICE_ATTR(_name, _mode, _cm)			\
+#define EEEPC_CREATE_DEVICE_ATTR_RW(_name, _cm)				\
 	EEEPC_ACPI_SHOW_FUNC(_name, _cm)				\
 	EEEPC_ACPI_STORE_FUNC(_name, _cm)				\
-	static DEVICE_ATTR(_name, _mode, _name##_show, _name##_store)
+	static DEVICE_ATTR_RW(_name)
 
-EEEPC_CREATE_DEVICE_ATTR(camera, 0644, CM_ASL_CAMERA);
-EEEPC_CREATE_DEVICE_ATTR(cardr, 0644, CM_ASL_CARDREADER);
-EEEPC_CREATE_DEVICE_ATTR(disp, 0200, CM_ASL_DISPLAYSWITCH);
+#define EEEPC_CREATE_DEVICE_ATTR_WO(_name, _cm)				\
+	EEEPC_ACPI_STORE_FUNC(_name, _cm)				\
+	static DEVICE_ATTR_WO(_name)
+
+EEEPC_CREATE_DEVICE_ATTR_RW(camera, CM_ASL_CAMERA);
+EEEPC_CREATE_DEVICE_ATTR_RW(cardr, CM_ASL_CARDREADER);
+EEEPC_CREATE_DEVICE_ATTR_WO(disp, CM_ASL_DISPLAYSWITCH);
 
 struct eeepc_cpufv {
 	int num;
-- 
2.1.0

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