linux-kernel - Re: [PATCH 2/3] i2c: attach/detach I2C client device to the ACPI power domain

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Date:	Thu, 10 Oct 2013 10:09:19 +0200
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:	linux-acpi@...r.kernel.org, Mark Brown <broonie@...nel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Aaron Lu <aaron.lu@...el.com>, Lv Zheng <lv.zheng@...el.com>,
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] i2c: attach/detach I2C client device to the ACPI
 power domain

On Wed, Oct 09, 2013 at 05:04:20PM +0300, Mika Westerberg wrote:
> From: Lv Zheng <lv.zheng@...el.com>
> 
> If the I2C client device is enumerated from ACPI namespace it might have
> ACPI methods that needs to be called in order to transition the device to
> different power states (such as _PSx).
> 
> Implement this for I2C client devices by checking if the device has an ACPI
> handle and if that's the case, attach it to the ACPI power domain. In
> addition we make sure that the device is fully powered when its ->probe()
> function gets called.
> 
> For non-ACPI devices this patch is a no-op.
> 
> Signed-off-by: Lv Zheng <lv.zheng@...el.com>
> Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> ---
>  drivers/i2c/i2c-core.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
> index 29d3f04..f25dee3 100644
> --- a/drivers/i2c/i2c-core.c
> +++ b/drivers/i2c/i2c-core.c
> @@ -254,10 +254,16 @@ static int i2c_device_probe(struct device *dev)
>  					client->flags & I2C_CLIENT_WAKE);
>  	dev_dbg(dev, "probe\n");
>  
> +	if (ACPI_HANDLE(&client->dev))
> +		acpi_dev_pm_attach(&client->dev, true);

I'd prefer to drop the 'if's in case they are checked inside the acpi_*
calls anyway. Not a show-stopper, though, so:

Acked-by: Wolfram Sang <wsa@...-dreams.de>


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