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Date:   Mon, 12 Apr 2021 11:30:03 -0600
From:   Mathieu Poirier <mathieu.poirier@linaro.org>
To:     Mike Leach <mike.leach@linaro.org>
Cc:     linux-arm-kernel@lists.infradead.org, coresight@lists.linaro.org,
        linux-doc@vger.kernel.org, suzuki.poulose@arm.com,
        yabinc@google.com, leo.yan@linaro.org,
        alexander.shishkin@linux.intel.com, tingwei@codeaurora.org,
        gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v6 09/10] coresight: syscfg: Add initial configfs support
Message-ID: <20210412173003.GA582195@xps15>
References: <20210409103722.26290-1-mike.leach@linaro.org>
 <20210409103722.26290-10-mike.leach@linaro.org>
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In-Reply-To: <20210409103722.26290-10-mike.leach@linaro.org>
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On Fri, Apr 09, 2021 at 11:37:21AM +0100, Mike Leach wrote:
> Adds configfs subsystem and attributes to the configuration manager
> to enable the listing of loaded configurations and features.
> 
> The default values of feature parameters can be accessed and altered
> from these attributes to affect all installed devices using the feature.
> 
> Signed-off-by: Mike Leach <mike.leach@linaro.org>
> ---
>  drivers/hwtracing/coresight/Makefile          |   3 +-
>  .../coresight/coresight-syscfg-configfs.c     | 396 ++++++++++++++++++
>  .../coresight/coresight-syscfg-configfs.h     |  45 ++
>  .../hwtracing/coresight/coresight-syscfg.c    |  76 ++++
>  .../hwtracing/coresight/coresight-syscfg.h    |   7 +
>  5 files changed, 526 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/hwtracing/coresight/coresight-syscfg-configfs.c
>  create mode 100644 drivers/hwtracing/coresight/coresight-syscfg-configfs.h
>

Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
 
> diff --git a/drivers/hwtracing/coresight/Makefile b/drivers/hwtracing/coresight/Makefile
> index ad44f0fe3069..b6c4a48140ec 100644
> --- a/drivers/hwtracing/coresight/Makefile
> +++ b/drivers/hwtracing/coresight/Makefile
> @@ -5,7 +5,8 @@
>  obj-$(CONFIG_CORESIGHT) += coresight.o
>  coresight-y := coresight-core.o  coresight-etm-perf.o coresight-platform.o \
>  		coresight-sysfs.o coresight-syscfg.o coresight-config.o \
> -		coresight-cfg-preload.o coresight-cfg-afdo.o
> +		coresight-cfg-preload.o coresight-cfg-afdo.o \
> +		coresight-syscfg-configfs.o
>  obj-$(CONFIG_CORESIGHT_LINK_AND_SINK_TMC) += coresight-tmc.o
>  coresight-tmc-y := coresight-tmc-core.o coresight-tmc-etf.o \
>  		      coresight-tmc-etr.o
> diff --git a/drivers/hwtracing/coresight/coresight-syscfg-configfs.c b/drivers/hwtracing/coresight/coresight-syscfg-configfs.c
> new file mode 100644
> index 000000000000..c547816b9000
> --- /dev/null
> +++ b/drivers/hwtracing/coresight/coresight-syscfg-configfs.c
> @@ -0,0 +1,396 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2020 Linaro Limited, All rights reserved.
> + * Author: Mike Leach <mike.leach@linaro.org>
> + */
> +
> +#include <linux/configfs.h>
> +
> +#include "coresight-syscfg-configfs.h"
> +
> +/* create a default ci_type. */
> +static inline struct config_item_type *cscfg_create_ci_type(void)
> +{
> +	struct config_item_type *ci_type;
> +
> +	ci_type = devm_kzalloc(cscfg_device(), sizeof(*ci_type), GFP_KERNEL);
> +	if (ci_type)
> +		ci_type->ct_owner = THIS_MODULE;
> +
> +	return ci_type;
> +}
> +
> +/* configurations sub-group */
> +
> +/* attributes for the config view group */
> +static ssize_t cscfg_cfg_description_show(struct config_item *item, char *page)
> +{
> +	struct cscfg_fs_config *fs_config = container_of(to_config_group(item),
> +							 struct cscfg_fs_config, group);
> +
> +	return scnprintf(page, PAGE_SIZE, "%s", fs_config->config_desc->description);
> +}
> +CONFIGFS_ATTR_RO(cscfg_cfg_, description);
> +
> +static ssize_t cscfg_cfg_feature_refs_show(struct config_item *item, char *page)
> +{
> +	struct cscfg_fs_config *fs_config = container_of(to_config_group(item),
> +							 struct cscfg_fs_config, group);
> +	const struct cscfg_config_desc *config_desc = fs_config->config_desc;
> +	ssize_t ch_used = 0;
> +	int i;
> +
> +	for (i = 0; i < config_desc->nr_feat_refs; i++)
> +		ch_used += scnprintf(page + ch_used, PAGE_SIZE - ch_used,
> +				     "%s\n", config_desc->feat_ref_names[i]);
> +	return ch_used;
> +}
> +CONFIGFS_ATTR_RO(cscfg_cfg_, feature_refs);
> +
> +/* list preset values in order of features and params */
> +static ssize_t cscfg_cfg_values_show(struct config_item *item, char *page)
> +{
> +	const struct cscfg_feature_desc *feat_desc;
> +	const struct cscfg_config_desc *config_desc;
> +	struct cscfg_fs_preset *fs_preset;
> +	int i, j, val_idx, preset_idx;
> +	ssize_t used = 0;
> +
> +	fs_preset = container_of(to_config_group(item), struct cscfg_fs_preset, group);
> +	config_desc = fs_preset->config_desc;
> +
> +	if (!config_desc->nr_presets)
> +		return 0;
> +
> +	preset_idx = fs_preset->preset_num - 1;
> +
> +	/* start index on the correct array line */
> +	val_idx = config_desc->nr_total_params * preset_idx;
> +
> +	/*
> +	 * A set of presets is the sum of all params in used features,
> +	 * in order of declaration of features and params in the features
> +	 */
> +	for (i = 0; i < config_desc->nr_feat_refs; i++) {
> +		feat_desc = cscfg_get_named_feat_desc(config_desc->feat_ref_names[i]);
> +		for (j = 0; j < feat_desc->nr_params; j++) {
> +			used += scnprintf(page + used, PAGE_SIZE - used,
> +					  "%s.%s = 0x%llx ",
> +					  feat_desc->name,
> +					  feat_desc->params_desc[j].name,
> +					  config_desc->presets[val_idx++]);
> +		}
> +	}
> +	used += scnprintf(page + used, PAGE_SIZE - used, "\n");
> +
> +	return used;
> +}
> +CONFIGFS_ATTR_RO(cscfg_cfg_, values);
> +
> +static struct configfs_attribute *cscfg_config_view_attrs[] = {
> +	&cscfg_cfg_attr_description,
> +	&cscfg_cfg_attr_feature_refs,
> +	NULL,
> +};
> +
> +static struct config_item_type cscfg_config_view_type = {
> +	.ct_owner = THIS_MODULE,
> +	.ct_attrs = cscfg_config_view_attrs,
> +};
> +
> +static struct configfs_attribute *cscfg_config_preset_attrs[] = {
> +	&cscfg_cfg_attr_values,
> +	NULL,
> +};
> +
> +static struct config_item_type cscfg_config_preset_type = {
> +	.ct_owner = THIS_MODULE,
> +	.ct_attrs = cscfg_config_preset_attrs,
> +};
> +
> +static int cscfg_add_preset_groups(struct cscfg_fs_config *cfg_view)
> +{
> +	int preset_num;
> +	struct cscfg_fs_preset *cfg_fs_preset;
> +	struct cscfg_config_desc *config_desc = cfg_view->config_desc;
> +	char name[CONFIGFS_ITEM_NAME_LEN];
> +
> +	if (!config_desc->nr_presets)
> +		return 0;
> +
> +	for (preset_num = 1; preset_num <= config_desc->nr_presets; preset_num++) {
> +		cfg_fs_preset = devm_kzalloc(cscfg_device(),
> +					     sizeof(struct cscfg_fs_preset), GFP_KERNEL);
> +
> +		if (!cfg_fs_preset)
> +			return -ENOMEM;
> +
> +		snprintf(name, CONFIGFS_ITEM_NAME_LEN, "preset%d", preset_num);
> +		cfg_fs_preset->preset_num = preset_num;
> +		cfg_fs_preset->config_desc = cfg_view->config_desc;
> +		config_group_init_type_name(&cfg_fs_preset->group, name,
> +					    &cscfg_config_preset_type);
> +		configfs_add_default_group(&cfg_fs_preset->group, &cfg_view->group);
> +	}
> +	return 0;
> +}
> +
> +static struct config_group *cscfg_create_config_group(struct cscfg_config_desc *config_desc)
> +{
> +	struct cscfg_fs_config *cfg_view;
> +	struct device *dev = cscfg_device();
> +	int err;
> +
> +	if (!dev)
> +		return ERR_PTR(-EINVAL);
> +
> +	cfg_view = devm_kzalloc(dev, sizeof(struct cscfg_fs_config), GFP_KERNEL);
> +	if (!cfg_view)
> +		return ERR_PTR(-ENOMEM);
> +
> +	cfg_view->config_desc = config_desc;
> +	config_group_init_type_name(&cfg_view->group, config_desc->name, &cscfg_config_view_type);
> +
> +	/* add in a preset<n> dir for each preset */
> +	err = cscfg_add_preset_groups(cfg_view);
> +	if (err)
> +		return ERR_PTR(err);
> +
> +	return &cfg_view->group;
> +}
> +
> +/* attributes for features view */
> +
> +static ssize_t cscfg_feat_description_show(struct config_item *item, char *page)
> +{
> +	struct cscfg_fs_feature *fs_feat = container_of(to_config_group(item),
> +							struct cscfg_fs_feature, group);
> +
> +	return scnprintf(page, PAGE_SIZE, "%s", fs_feat->feat_desc->description);
> +}
> +CONFIGFS_ATTR_RO(cscfg_feat_, description);
> +
> +static ssize_t cscfg_feat_matches_show(struct config_item *item, char *page)
> +{
> +	struct cscfg_fs_feature *fs_feat = container_of(to_config_group(item),
> +							struct cscfg_fs_feature, group);
> +	u32 match_flags = fs_feat->feat_desc->match_flags;
> +	int used = 0;
> +
> +	if (match_flags & CS_CFG_MATCH_CLASS_SRC_ALL)
> +		used = scnprintf(page, PAGE_SIZE, "SRC_ALL ");
> +
> +	if (match_flags & CS_CFG_MATCH_CLASS_SRC_ETM4)
> +		used += scnprintf(page + used, PAGE_SIZE - used, "SRC_ETMV4 ");
> +
> +	used += scnprintf(page + used, PAGE_SIZE - used, "\n");
> +	return used;
> +}
> +CONFIGFS_ATTR_RO(cscfg_feat_, matches);
> +
> +static ssize_t cscfg_feat_nr_params_show(struct config_item *item, char *page)
> +{
> +	struct cscfg_fs_feature *fs_feat = container_of(to_config_group(item),
> +							struct cscfg_fs_feature, group);
> +
> +	return scnprintf(page, PAGE_SIZE, "%d\n", fs_feat->feat_desc->nr_params);
> +}
> +CONFIGFS_ATTR_RO(cscfg_feat_, nr_params);
> +
> +/* base feature desc attrib structures */
> +static struct configfs_attribute *cscfg_feature_view_attrs[] = {
> +	&cscfg_feat_attr_description,
> +	&cscfg_feat_attr_matches,
> +	&cscfg_feat_attr_nr_params,
> +	NULL,
> +};
> +
> +static struct config_item_type cscfg_feature_view_type = {
> +	.ct_owner = THIS_MODULE,
> +	.ct_attrs = cscfg_feature_view_attrs,
> +};
> +
> +static ssize_t cscfg_param_value_show(struct config_item *item, char *page)
> +{
> +	struct cscfg_fs_param *param_item = container_of(to_config_group(item),
> +							 struct cscfg_fs_param, group);
> +	u64 value = param_item->feat_desc->params_desc[param_item->param_idx].value;
> +
> +	return scnprintf(page, PAGE_SIZE, "0x%llx\n", value);
> +}
> +
> +static ssize_t cscfg_param_value_store(struct config_item *item,
> +				       const char *page, size_t size)
> +{
> +	struct cscfg_fs_param *param_item = container_of(to_config_group(item),
> +							 struct cscfg_fs_param, group);
> +	struct cscfg_feature_desc *feat_desc = param_item->feat_desc;
> +	int param_idx = param_item->param_idx;
> +	u64 value;
> +	int err;
> +
> +	err = kstrtoull(page, 0, &value);
> +	if (!err)
> +		err = cscfg_update_feat_param_val(feat_desc, param_idx, value);
> +
> +	return err ? err : size;
> +}
> +CONFIGFS_ATTR(cscfg_param_, value);
> +
> +static struct configfs_attribute *cscfg_param_view_attrs[] = {
> +	&cscfg_param_attr_value,
> +	NULL,
> +};
> +
> +static struct config_item_type cscfg_param_view_type = {
> +	.ct_owner = THIS_MODULE,
> +	.ct_attrs = cscfg_param_view_attrs,
> +};
> +
> +/*
> + * configfs has far less functionality provided to add attributes dynamically than sysfs,
> + * and the show and store fns pass the enclosing config_item so the actual attribute cannot
> + * be determined. Therefore we add each item as a group directory, with a value attribute.
> + */
> +static int cscfg_create_params_group_items(struct cscfg_feature_desc *feat_desc,
> +					   struct config_group *params_group)
> +{
> +	struct device *dev = cscfg_device();
> +	struct cscfg_fs_param *param_item;
> +	int i;
> +
> +	/* parameter items - as groups with default_value attribute */
> +	for (i = 0; i < feat_desc->nr_params; i++) {
> +		param_item = devm_kzalloc(dev, sizeof(struct cscfg_fs_param), GFP_KERNEL);
> +		if (!param_item)
> +			return -ENOMEM;
> +		param_item->feat_desc = feat_desc;
> +		param_item->param_idx = i;
> +		config_group_init_type_name(&param_item->group,
> +					    feat_desc->params_desc[i].name,
> +					    &cscfg_param_view_type);
> +		configfs_add_default_group(&param_item->group, params_group);
> +	}
> +	return 0;
> +}
> +
> +static struct config_group *cscfg_create_feature_group(struct cscfg_feature_desc *feat_desc)
> +{
> +	struct cscfg_fs_feature *feat_view;
> +	struct config_item_type *params_group_type;
> +	struct config_group *params_group = NULL;
> +	struct device *dev = cscfg_device();
> +	int item_err;
> +
> +	if (!dev)
> +		return ERR_PTR(-EINVAL);
> +
> +	feat_view = devm_kzalloc(dev, sizeof(struct cscfg_fs_feature), GFP_KERNEL);
> +	if (!feat_view)
> +		return ERR_PTR(-ENOMEM);
> +
> +	if (feat_desc->nr_params) {
> +		params_group = devm_kzalloc(dev, sizeof(struct config_group), GFP_KERNEL);
> +		if (!params_group)
> +			return ERR_PTR(-ENOMEM);
> +
> +		params_group_type = cscfg_create_ci_type();
> +		if (!params_group_type)
> +			return ERR_PTR(-ENOMEM);
> +	}
> +
> +	feat_view->feat_desc = feat_desc;
> +	config_group_init_type_name(&feat_view->group,
> +				    feat_desc->name,
> +				    &cscfg_feature_view_type);
> +	if (params_group) {
> +		config_group_init_type_name(params_group, "params", params_group_type);
> +		configfs_add_default_group(params_group, &feat_view->group);
> +		item_err = cscfg_create_params_group_items(feat_desc, params_group);
> +		if (item_err)
> +			return ERR_PTR(item_err);
> +	}
> +	return &feat_view->group;
> +}
> +
> +static struct config_item_type cscfg_configs_type = {
> +	.ct_owner = THIS_MODULE,
> +};
> +
> +static struct config_group cscfg_configs_grp = {
> +	.cg_item = {
> +		.ci_namebuf = "configurations",
> +		.ci_type = &cscfg_configs_type,
> +	},
> +};
> +
> +/* add configuration to configurations group */
> +int cscfg_configfs_add_config(struct cscfg_config_desc *config_desc)
> +{
> +	struct config_group *new_group;
> +	int err;
> +
> +	new_group = cscfg_create_config_group(config_desc);
> +	if (IS_ERR(new_group))
> +		return PTR_ERR(new_group);
> +	err =  configfs_register_group(&cscfg_configs_grp, new_group);
> +	return err;
> +}
> +
> +static struct config_item_type cscfg_features_type = {
> +	.ct_owner = THIS_MODULE,
> +};
> +
> +static struct config_group cscfg_features_grp = {
> +	.cg_item = {
> +		.ci_namebuf = "features",
> +		.ci_type = &cscfg_features_type,
> +	},
> +};
> +
> +/* add feature to features group */
> +int cscfg_configfs_add_feature(struct cscfg_feature_desc *feat_desc)
> +{
> +	struct config_group *new_group;
> +	int err;
> +
> +	new_group = cscfg_create_feature_group(feat_desc);
> +	if (IS_ERR(new_group))
> +		return PTR_ERR(new_group);
> +	err =  configfs_register_group(&cscfg_features_grp, new_group);
> +	return err;
> +}
> +
> +int cscfg_configfs_init(struct cscfg_manager *cscfg_mgr)
> +{
> +	struct configfs_subsystem *subsys;
> +	struct config_item_type *ci_type;
> +
> +	if (!cscfg_mgr)
> +		return -EINVAL;
> +
> +	ci_type = cscfg_create_ci_type();
> +	if (!ci_type)
> +		return -ENOMEM;
> +
> +	subsys = &cscfg_mgr->cfgfs_subsys;
> +	config_item_set_name(&subsys->su_group.cg_item, CSCFG_FS_SUBSYS_NAME);
> +	subsys->su_group.cg_item.ci_type = ci_type;
> +
> +	config_group_init(&subsys->su_group);
> +	mutex_init(&subsys->su_mutex);
> +
> +	/* Add default groups to subsystem */
> +	config_group_init(&cscfg_configs_grp);
> +	configfs_add_default_group(&cscfg_configs_grp, &subsys->su_group);
> +
> +	config_group_init(&cscfg_features_grp);
> +	configfs_add_default_group(&cscfg_features_grp, &subsys->su_group);
> +
> +	return configfs_register_subsystem(subsys);
> +}
> +
> +void cscfg_configfs_release(struct cscfg_manager *cscfg_mgr)
> +{
> +	configfs_unregister_subsystem(&cscfg_mgr->cfgfs_subsys);
> +}
> diff --git a/drivers/hwtracing/coresight/coresight-syscfg-configfs.h b/drivers/hwtracing/coresight/coresight-syscfg-configfs.h
> new file mode 100644
> index 000000000000..7d6ffe35ca4c
> --- /dev/null
> +++ b/drivers/hwtracing/coresight/coresight-syscfg-configfs.h
> @@ -0,0 +1,45 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Coresight system configuration driver - support for configfs.
> + */
> +
> +#ifndef CORESIGHT_SYSCFG_CONFIGFS_H
> +#define CORESIGHT_SYSCFG_CONFIGFS_H
> +
> +#include <linux/configfs.h>
> +#include "coresight-syscfg.h"
> +
> +#define CSCFG_FS_SUBSYS_NAME "cs-syscfg"
> +
> +/* container for configuration view */
> +struct cscfg_fs_config {
> +	struct cscfg_config_desc *config_desc;
> +	struct config_group group;
> +};
> +
> +/* container for feature view */
> +struct cscfg_fs_feature {
> +	struct cscfg_feature_desc *feat_desc;
> +	struct config_group group;
> +};
> +
> +/* container for parameter view */
> +struct cscfg_fs_param {
> +	int param_idx;
> +	struct cscfg_feature_desc *feat_desc;
> +	struct config_group group;
> +};
> +
> +/* container for preset view */
> +struct cscfg_fs_preset {
> +	int preset_num;
> +	struct cscfg_config_desc *config_desc;
> +	struct config_group group;
> +};
> +
> +int cscfg_configfs_init(struct cscfg_manager *cscfg_mgr);
> +void cscfg_configfs_release(struct cscfg_manager *cscfg_mgr);
> +int cscfg_configfs_add_config(struct cscfg_config_desc *config_desc);
> +int cscfg_configfs_add_feature(struct cscfg_feature_desc *feat_desc);
> +
> +#endif /* CORESIGHT_SYSCFG_CONFIGFS_H */
> diff --git a/drivers/hwtracing/coresight/coresight-syscfg.c b/drivers/hwtracing/coresight/coresight-syscfg.c
> index 41f742190639..180202402eb5 100644
> --- a/drivers/hwtracing/coresight/coresight-syscfg.c
> +++ b/drivers/hwtracing/coresight/coresight-syscfg.c
> @@ -9,6 +9,7 @@
>  #include "coresight-config.h"
>  #include "coresight-etm-perf.h"
>  #include "coresight-syscfg.h"
> +#include "coresight-syscfg-configfs.h"
>  
>  /*
>   * cscfg_ API manages configurations and features for the entire coresight
> @@ -287,6 +288,72 @@ static int cscfg_load_config(struct cscfg_config_desc *config_desc)
>  	return 0;
>  }
>  
> +/* get a feature descriptor by name */
> +const struct cscfg_feature_desc *cscfg_get_named_feat_desc(const char *name)
> +{
> +	const struct cscfg_feature_desc *feat_desc = NULL, *feat_desc_item;
> +
> +	mutex_lock(&cscfg_mutex);
> +
> +	list_for_each_entry(feat_desc_item, &cscfg_mgr->feat_desc_list, item) {
> +		if (strcmp(feat_desc_item->name, name) == 0) {
> +			feat_desc = feat_desc_item;
> +			break;
> +		}
> +	}
> +
> +	mutex_unlock(&cscfg_mutex);
> +	return feat_desc;
> +}
> +
> +/* called with cscfg_mutex held */
> +static struct cscfg_feature_csdev *
> +cscfg_csdev_get_feat_from_desc(struct coresight_device *csdev,
> +			       struct cscfg_feature_desc *feat_desc)
> +{
> +	struct cscfg_feature_csdev *feat_csdev;
> +
> +	list_for_each_entry(feat_csdev, &csdev->feature_csdev_list, node) {
> +		if (feat_csdev->feat_desc == feat_desc)
> +			return feat_csdev;
> +	}
> +	return NULL;
> +}
> +
> +int cscfg_update_feat_param_val(struct cscfg_feature_desc *feat_desc,
> +				int param_idx, u64 value)
> +{
> +	int err = 0;
> +	struct cscfg_feature_csdev *feat_csdev;
> +	struct cscfg_registered_csdev *csdev_item;
> +
> +	mutex_lock(&cscfg_mutex);
> +
> +	/* check if any config active & return busy */
> +	if (atomic_read(&cscfg_mgr->sys_active_cnt)) {
> +		err = -EBUSY;
> +		goto unlock_exit;
> +	}
> +
> +	/* set the value */
> +	if ((param_idx < 0) || (param_idx >= feat_desc->nr_params)) {
> +		err = -EINVAL;
> +		goto unlock_exit;
> +	}
> +	feat_desc->params_desc[param_idx].value = value;
> +
> +	/* update loaded instances.*/
> +	list_for_each_entry(csdev_item, &cscfg_mgr->csdev_desc_list, item) {
> +		feat_csdev = cscfg_csdev_get_feat_from_desc(csdev_item->csdev, feat_desc);
> +		if (feat_csdev)
> +			feat_csdev->params_csdev[param_idx].current_value = value;
> +	}
> +
> +unlock_exit:
> +	mutex_unlock(&cscfg_mutex);
> +	return err;
> +}
> +
>  /**
>   * cscfg_load_config_sets - API function to load feature and config sets.
>   *
> @@ -308,6 +375,8 @@ int cscfg_load_config_sets(struct cscfg_config_desc **config_descs,
>  	if (feat_descs) {
>  		while (feat_descs[i]) {
>  			err = cscfg_load_feat(feat_descs[i]);
> +			if (!err)
> +				err = cscfg_configfs_add_feature(feat_descs[i]);
>  			if (err) {
>  				pr_err("coresight-syscfg: Failed to load feature %s\n",
>  				       feat_descs[i]->name);
> @@ -322,6 +391,8 @@ int cscfg_load_config_sets(struct cscfg_config_desc **config_descs,
>  	if (config_descs) {
>  		while (config_descs[i]) {
>  			err = cscfg_load_config(config_descs[i]);
> +			if (!err)
> +				err = cscfg_configfs_add_config(config_descs[i]);
>  			if (err) {
>  				pr_err("coresight-syscfg: Failed to load configuration %s\n",
>  				       config_descs[i]->name);
> @@ -691,6 +762,7 @@ static void cscfg_clear_device(void)
>  	list_for_each_entry(cfg_desc, &cscfg_mgr->config_desc_list, item) {
>  		etm_perf_del_symlink_cscfg(cfg_desc);
>  	}
> +	cscfg_configfs_release(cscfg_mgr);
>  	device_unregister(cscfg_device());
>  	mutex_unlock(&cscfg_mutex);
>  }
> @@ -704,6 +776,10 @@ int __init cscfg_init(void)
>  	if (err)
>  		return err;
>  
> +	err = cscfg_configfs_init(cscfg_mgr);
> +	if (err)
> +		goto exit_err;
> +
>  	INIT_LIST_HEAD(&cscfg_mgr->csdev_desc_list);
>  	INIT_LIST_HEAD(&cscfg_mgr->feat_desc_list);
>  	INIT_LIST_HEAD(&cscfg_mgr->config_desc_list);
> diff --git a/drivers/hwtracing/coresight/coresight-syscfg.h b/drivers/hwtracing/coresight/coresight-syscfg.h
> index 7bb8c8e497ba..8d018efd6ead 100644
> --- a/drivers/hwtracing/coresight/coresight-syscfg.h
> +++ b/drivers/hwtracing/coresight/coresight-syscfg.h
> @@ -6,6 +6,7 @@
>  #ifndef CORESIGHT_SYSCFG_H
>  #define CORESIGHT_SYSCFG_H
>  
> +#include <linux/configfs.h>
>  #include <linux/coresight.h>
>  #include <linux/device.h>
>  
> @@ -25,6 +26,7 @@
>   * @feat_desc_list:	List of feature descriptors to load into registered devices.
>   * @config_desc_list:	List of system configuration descriptors to load into registered devices.
>   * @sys_active_cnt:	Total number of active config descriptor references.
> + * @cfgfs_subsys:	configfs subsystem used to manage configurations.
>   */
>  struct cscfg_manager {
>  	struct device dev;
> @@ -32,6 +34,7 @@ struct cscfg_manager {
>  	struct list_head feat_desc_list;
>  	struct list_head config_desc_list;
>  	atomic_t sys_active_cnt;
> +	struct configfs_subsystem cfgfs_subsys;
>  };
>  
>  /* get reference to dev in cscfg_manager */
> @@ -57,6 +60,10 @@ struct cscfg_registered_csdev {
>  int __init cscfg_init(void);
>  void cscfg_exit(void);
>  int cscfg_preload(void);
> +const struct cscfg_feature_desc *cscfg_get_named_feat_desc(const char *name);
> +int cscfg_update_feat_param_val(struct cscfg_feature_desc *feat_desc,
> +				int param_idx, u64 value);
> +
>  
>  /* syscfg manager external API */
>  int cscfg_load_config_sets(struct cscfg_config_desc **cfg_descs,
> -- 
> 2.17.1
>