[PATCH] nvme: add 'kato' sysfs attribute

[George, Martin]

On Fri, 2021-02-26 at 08:52 +0100, Hannes Reinecke wrote:
> Add a 'kato' controller sysfs attribute to display the current
> keep-alive timeout value (if any). This allows userspace to identify
> persistent discovery controllers, as these will have a non-zero
> KATO value.
> 
> Signed-off-by: Hannes Reinecke <hare at suse.de>
> ---
>  drivers/nvme/host/core.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index 1d5fc8a6fd37..9ad23472ac15 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -3547,6 +3547,7 @@ nvme_show_int_function(cntlid);
>  nvme_show_int_function(numa_node);
>  nvme_show_int_function(queue_count);
>  nvme_show_int_function(sqsize);
> +nvme_show_int_function(kato);
> 
>  static ssize_t nvme_sysfs_delete(struct device *dev,
>                                 struct device_attribute *attr, const
> char *buf,
> @@ -3749,6 +3750,7 @@ static struct attribute *nvme_dev_attrs[] = {
>         &dev_attr_ctrl_loss_tmo.attr,
>         &dev_attr_fast_io_fail_tmo.attr,
>         &dev_attr_reconnect_delay.attr,
> +       &dev_attr_kato.attr,
>         NULL
>  };
> 

This is helpful indeed. But looks like the actual kato value sent down
the wire is ctrl->kato + NVME_KATO_GRACE. Wondering if that may end up
confusing the end user.

-Martin