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

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Date:	Mon, 15 Sep 2014 13:00:07 -0700
From:	Darren Hart <dvhart@...radead.org>
To:	Frans Klaver <fransklaver@...il.com>
Cc:	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: Re: [PATCH 07/13] eeepc-laptop: make disp attribute really write-only

On Sat, Sep 13, 2014 at 01:06:46AM +0200, Frans Klaver wrote:
> 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)

Per Greg's previous reply, I presume DEVICE_ATTR_WO here?

> +
>  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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> 

-- 
Darren Hart
Intel Open Source Technology Center
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