On Tue, Mar 16, 2021 at 06:03:59PM +0000, 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.le...@linaro.org>
> ---
>  drivers/hwtracing/coresight/Makefile          |   3 +-
>  .../coresight/coresight-syscfg-configfs.c     | 399 ++++++++++++++++++
>  .../coresight/coresight-syscfg-configfs.h     |  45 ++
>  .../hwtracing/coresight/coresight-syscfg.c    |  77 ++++
>  .../hwtracing/coresight/coresight-syscfg.h    |   7 +
>  5 files changed, 530 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/hwtracing/coresight/coresight-syscfg-configfs.c
>  create mode 100644 drivers/hwtracing/coresight/coresight-syscfg-configfs.h
> 
> diff --git a/drivers/hwtracing/coresight/Makefile 
> b/drivers/hwtracing/coresight/Makefile
> index 2707bfef1b76..391c93a08902 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..7cefad81d1f6
> --- /dev/null
> +++ b/drivers/hwtracing/coresight/coresight-syscfg-configfs.c
> @@ -0,0 +1,399 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2020 Linaro Limited, All rights reserved.
> + * Author: Mike Leach <mike.le...@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\n", 
> 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;
> +
> +     if (config_desc->nr_feat_refs) {

This check isn't needed.

> +             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\n", 
> fs_feat->feat_desc->description);

Either remove the '\n' at the end of fs_feat->feat_desc->description or above,
with a preference toward the former.  The same thing should be done for
cscfg_cfg_description_show().

Otherwise it creates and exta new line when quering from the command line and it
is only a matter of time before the automated tools point it out.

> +}
> +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 befc379b85b9..3be3828a40a7 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
> @@ -288,6 +289,72 @@ 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;
> +}
> +
>  /*
>   * External API function to load feature and config sets.
>   * Take a 0 terminated array of feature descriptors and/or configuration
> @@ -305,6 +372,8 @@ 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);
> @@ -319,6 +388,8 @@ 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);
> @@ -608,6 +679,7 @@ int cscfg_create_device(void)
>       dev->init_name = "cs_system_cfg";
>  
>       err = device_register(dev);
> +

Spurious change

I am done reviewing your work.  Before sending another revision please
ensure everything works properly when applied on top of the ETE/TRBE 
patchset[1].
It applies correctly but I'm not sure it does the right thing, especially in
etm_setup_aux() with the per CPU handle changes that have been introduced.

Thanks,
Mathieu

[1]. 
https://git.kernel.org/pub/scm/linux/kernel/git/coresight/linux.git/log/?h=next-ETE-TRBE


>       if (err)
>               cscfg_dev_release(dev);
>  
> @@ -624,6 +696,7 @@ 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);
>  }
> @@ -637,6 +710,10 @@ 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
> 

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