Re: [PATCH v4] Drivers: hv: vmbus: Expose monitor data only when monitor pages are used

[Greg KH]

On Fri, Mar 01, 2019 at 02:18:24PM -0500, Kimberly Brown wrote:
> +/*
> + * Channel-level attribute_group callback function. Returns the permission for
> + * each attribute, and returns 0 if an attribute is not visible.
> + */
> +static umode_t vmbus_chan_attr_is_visible(struct kobject *kobj,
> +					  struct attribute *attr, int idx)
> +{
> +	const struct vmbus_channel *channel =
> +		container_of(kobj, struct vmbus_channel, kobj);
> +
> +	/* Hide the monitor attributes if the monitor mechanism is not used. */
> +	if (!channel->offermsg.monitor_allocated &&
> +	    (attr == &chan_attr_pending.attr ||
> +	     attr == &chan_attr_latency.attr ||
> +	     attr == &chan_attr_monitor_id.attr))
> +		return 0;
> +
> +	return attr->mode;
> +}
> +
> +static struct attribute_group vmbus_chan_group = {
> +	.attrs = vmbus_chan_attrs,
> +	.is_visible = vmbus_chan_attr_is_visible
> +};
> +
>  static struct kobj_type vmbus_chan_ktype = {
>  	.sysfs_ops = &vmbus_chan_sysfs_ops,
>  	.release = vmbus_chan_release,
> -	.default_attrs = vmbus_chan_attrs,

Why did you remove this line?

>  };
>  
>  /*
> @@ -1571,6 +1624,12 @@ int vmbus_add_channel_kobj(struct hv_device *dev, struct vmbus_channel *channel)
>  	if (ret)
>  		return ret;
>  
> +	ret = sysfs_create_group(kobj, &vmbus_chan_group);

Why are you adding these "by hand"?  What was wrong with using the
default attribute group pointer?  You also are not removing the
attributes :(

greg k-h