Subject: Re: [PATCH v4 3/6] coresight: Add generic sysfs link creation functions.

From: Mathieu Poirier <[email-masked]>
Date: Fri, 14 Feb 2020 16:17:06 -0700

On Tue, Feb 11, 2020 at 10:58:05AM +0000, Mike Leach wrote:
> To allow the connections between coresight components to be represented
> in sysfs, generic methods for creating sysfs links between two coresight
> devices are added.
> 
> Signed-off-by: Mike Leach <[email-masked]>
> Reviewed-by: Suzuki K Poulose <[email-masked]>
> ---
>  drivers/hwtracing/coresight/Makefile          |   3 +-
>  drivers/hwtracing/coresight/coresight-priv.h  |   4 +
>  drivers/hwtracing/coresight/coresight-sysfs.c | 124 ++++++++++++++++++
>  include/linux/coresight.h                     |  20 +++
>  4 files changed, 150 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/hwtracing/coresight/coresight-sysfs.c
> 
> diff --git a/drivers/hwtracing/coresight/Makefile b/drivers/hwtracing/coresight/Makefile
> index 0e3e72f0f510..19497d1d92bf 100644
> --- a/drivers/hwtracing/coresight/Makefile
> +++ b/drivers/hwtracing/coresight/Makefile
> @@ -2,7 +2,8 @@
>  #
>  # Makefile for CoreSight drivers.
>  #
> -obj-$(CONFIG_CORESIGHT) += coresight.o coresight-etm-perf.o coresight-platform.o
> +obj-$(CONFIG_CORESIGHT) += coresight.o coresight-etm-perf.o \
> +			   coresight-platform.o coresight-sysfs.o
>  obj-$(CONFIG_CORESIGHT_LINK_AND_SINK_TMC) += coresight-tmc.o \
>  					     coresight-tmc-etf.o \
>  					     coresight-tmc-etr.o
> diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
> index 1cad642f27aa..a4a658d46045 100644
> --- a/drivers/hwtracing/coresight/coresight-priv.h
> +++ b/drivers/hwtracing/coresight/coresight-priv.h
> @@ -153,6 +153,10 @@ struct coresight_device *coresight_get_sink_by_id(u32 id);
>  struct list_head *coresight_build_path(struct coresight_device *csdev,
>  				       struct coresight_device *sink);
>  void coresight_release_path(struct list_head *path);
> +int coresight_add_sysfs_link(struct coresight_sysfs_link *info);
> +void coresight_remove_sysfs_link(struct coresight_sysfs_link *info);
> +int coresight_create_conns_sysfs_group(struct coresight_device *csdev);
> +void coresight_remove_conns_sysfs_group(struct coresight_device *csdev);
>  
>  #ifdef CONFIG_CORESIGHT_SOURCE_ETM3X
>  extern int etm_readl_cp14(u32 off, unsigned int *val);
> diff --git a/drivers/hwtracing/coresight/coresight-sysfs.c b/drivers/hwtracing/coresight/coresight-sysfs.c
> new file mode 100644
> index 000000000000..17d565941e5e
> --- /dev/null
> +++ b/drivers/hwtracing/coresight/coresight-sysfs.c
> @@ -0,0 +1,124 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2019, Linaro Limited, All rights reserved.
> + * Author: Mike Leach <[email-masked]>
> + */
> +
> +#include <linux/device.h>
> +#include <linux/kernel.h>
> +
> +#include "coresight-priv.h"
> +
> +/*
> + * Connections group - links attribute.
> + * Count of created links between coresight components in the group.
> + */
> +static ssize_t nr_links_show(struct device *dev,
> +			     struct device_attribute *attr,
> +			     char *buf)
> +{
> +	struct coresight_device *csdev = to_coresight_device(dev);
> +
> +	return scnprintf(buf, PAGE_SIZE, "%d\n", csdev->nr_links);
> +}
> +static DEVICE_ATTR_RO(nr_links);
> +
> +static struct attribute *coresight_conns_attrs[] = {
> +	&dev_attr_nr_links.attr,
> +	NULL,
> +};
> +
> +static struct attribute_group coresight_conns_group = {
> +	.attrs = coresight_conns_attrs,
> +	.name = "connections",
> +};
> +
> +/*
> + * Create connections group for CoreSight devices.
> + * This group will then be used to collate the sysfs links between
> + * devices.
> + */
> +int coresight_create_conns_sysfs_group(struct coresight_device *csdev)
> +{
> +	int ret = 0;
> +
> +	if (!csdev)
> +		return -EINVAL;
> +
> +	ret = sysfs_create_group(&csdev->dev.kobj, &coresight_conns_group);
> +	if (ret)
> +		return ret;
> +
> +	csdev->has_conns_grp = true;

The only place coresight_create_conns_sysfs_group() is used is in
coresight_register() where an error is returned to driver probe() functions if
an error occurs.  Have you found places where csdev->has_conns_grp is needed?
If not please remove.

> +	return ret;
> +}
> +
> +void coresight_remove_conns_sysfs_group(struct coresight_device *csdev)
> +{
> +	if (!csdev)
> +		return;
> +
> +	if (csdev->has_conns_grp) {
> +		sysfs_remove_group(&csdev->dev.kobj, &coresight_conns_group);
> +		csdev->has_conns_grp = false;
> +	}
> +}
> +
> +int coresight_add_sysfs_link(struct coresight_sysfs_link *info)
> +{
> +	int ret = 0;
> +
> +	if (!info)
> +		return -EINVAL;
> +	if (!info->orig || !info->target ||
> +	    !info->orig_name || !info->target_name)
> +		return -EINVAL;
> +	if (!info->orig->has_conns_grp || !info->target->has_conns_grp)
> +		return -EINVAL;
> +
> +	/* first link orig->target */
> +	ret = sysfs_add_link_to_group(&info->orig->dev.kobj,
> +				      coresight_conns_group.name,
> +				      &info->target->dev.kobj,
> +				      info->orig_name);
> +	if (ret)
> +		return ret;
> +
> +	/* second link target->orig */
> +	ret = sysfs_add_link_to_group(&info->target->dev.kobj,
> +				      coresight_conns_group.name,
> +				      &info->orig->dev.kobj,
> +				      info->target_name);
> +
> +	/* error in second link - remove first - otherwise inc counts */
> +	if (ret) {
> +		sysfs_remove_link_from_group(&info->orig->dev.kobj,
> +					     coresight_conns_group.name,
> +					     info->orig_name);
> +	} else {
> +		info->orig->nr_links++;
> +		info->target->nr_links++;
> +	}
> +
> +	return ret;
> +}
> +
> +void coresight_remove_sysfs_link(struct coresight_sysfs_link *info)
> +{
> +	if (!info)
> +		return;
> +	if (!info->orig || !info->target ||
> +	    !info->orig_name || !info->target_name)
> +		return;
> +
> +	sysfs_remove_link_from_group(&info->orig->dev.kobj,
> +				     coresight_conns_group.name,
> +				     info->orig_name);
> +
> +	sysfs_remove_link_from_group(&info->target->dev.kobj,
> +				     coresight_conns_group.name,
> +				     info->target_name);
> +
> +	info->orig->nr_links--;
> +	info->target->nr_links--;
> +}
> diff --git a/include/linux/coresight.h b/include/linux/coresight.h
> index 193cc9dbf448..a2ec25e02ca9 100644
> --- a/include/linux/coresight.h
> +++ b/include/linux/coresight.h
> @@ -148,6 +148,20 @@ struct coresight_connection {
>  	struct coresight_device *child_dev;
>  };
>  
> +/**
> + * struct coresight_sysfs_link - representation of a connection in sysfs.
> + * @orig:		Originating (master) coresight device for the link.
> + * @orig_name:		Name to use for the link orig->target.
> + * @target:		Target (slave) coresight device for the link.
> + * @target_name:	Name to use for the link target->orig.
> + */
> +struct coresight_sysfs_link {
> +	struct coresight_device *orig;
> +	const char *orig_name;
> +	struct coresight_device *target;
> +	const char *target_name;
> +};
> +
>  /**
>   * struct coresight_device - representation of a device as used by the framework
>   * @pdata:	Platform data with device connections associated to this device.
> @@ -165,6 +179,9 @@ struct coresight_connection {
>   * @ea:		Device attribute for sink representation under PMU directory.
>   * @ect_dev:	Associated cross trigger device. Not part of the trace data
>   *		path or connections.
> + * @nr_links:   number of sysfs links created to other components from this
> + *		device. These will appear in the "connections" group.
> + * @has_conns_grp: Have added a "connections" group for sysfs links.
>   */
>  struct coresight_device {
>  	struct coresight_platform_data *pdata;
> @@ -180,6 +197,9 @@ struct coresight_device {
>  	struct dev_ext_attribute *ea;
>  	/* cross trigger handling */
>  	struct coresight_device *ect_dev;
> +	/* sysfs links between components */
> +	int nr_links;
> +	bool has_conns_grp;
>  };

With the above: 

Reviewed-by: Mathieu Poirier <[email-masked]>

>  /*
> -- 
> 2.17.1

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