Re: [PATCH v2 3/3] powerpc/pseries: Report in kernel device tree update to drmgr

[Nathan Fontenot <nfont@linux.vnet.ibm.com>]

On 01/22/2014 01:58 PM, Tyrel Datwyler wrote:
> Traditionally it has been drmgr's responsibilty to update the device tree
> through the /proc/ppc64/ofdt interface after a suspend/resume operation.
> This patchset however has modified suspend/resume ops to preform that update
> entirely in the kernel during the resume. Therefore, a mechanism is required
> for drmgr to determine who is responsible for the update. This patch adds a
> show function to the "hibernate" attribute that returns 1 if the kernel
> updates the device tree after the resume and 0 if drmgr is responsible.
> 
> Signed-off-by: Tyrel Datwyler <tyreld@linux.vnet.ibm.com>

Acked-by: Nathan Fontenot <nfont@linux.vnet.ibm.com>

> ---
>  arch/powerpc/platforms/pseries/suspend.c | 25 ++++++++++++++++++++++++-
>  1 file changed, 24 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/platforms/pseries/suspend.c b/arch/powerpc/platforms/pseries/suspend.c
> index 16a2552..723115d 100644
> --- a/arch/powerpc/platforms/pseries/suspend.c
> +++ b/arch/powerpc/platforms/pseries/suspend.c
> @@ -174,7 +174,30 @@ out:
>  	return rc;
>  }
> 
> -static DEVICE_ATTR(hibernate, S_IWUSR, NULL, store_hibernate);
> +#define USER_DT_UPDATE	0
> +#define KERN_DT_UPDATE	1
> +
> +/**
> + * show_hibernate - Report device tree update responsibilty
> + * @dev:		subsys root device
> + * @attr:		device attribute struct
> + * @buf:		buffer
> + *
> + * Report whether a device tree update is performed by the kernel after a
> + * resume, or if drmgr must coordinate the update from user space.
> + *
> + * Return value:
> + *	0 if drmgr is to initiate update, and 1 otherwise
> + **/
> +static ssize_t show_hibernate(struct device *dev,
> +			      struct device_attribute *attr,
> +			      char *buf)
> +{
> +	return sprintf(buf, "%d\n", KERN_DT_UPDATE);
> +}
> +
> +static DEVICE_ATTR(hibernate, S_IWUSR | S_IRUGO,
> +		   show_hibernate, store_hibernate);
> 
>  static struct bus_type suspend_subsys = {
>  	.name = "power",
>