Re: [PATCH v4 3/7] coresight: syscfg: Match feature capabilities separately from device class

[James Clark <james.clark@linaro.org>]

On 26/10/2026 05:48, Amir Ayupov wrote:
> A feature loads on a device when the two share any match flag. That works
> for device classes, where a feature wants any one of them, but not for
> capabilities a device may or may not have: a feature that sets a class
> and a capability would still load on a device of that class without the
> capability.
> 
> Split the match flags into CS_CFG_MATCH_CLASS_MASK for device classes and
> CS_CFG_MATCH_CAP_MASK for capabilities. A feature now loads on a device
> that shares one of its classes and has all of its capabilities. Check
> this once in cscfg_load_feat_csdev(), which both the feature and the
> device registration paths call. No capability flags are defined yet, so
> matching is unchanged.
> 
> Assisted-by: Devmate:Opus-5.5
> Signed-off-by: Amir Ayupov <aaupov@fb.com>
> ---
>   .../hwtracing/coresight/coresight-config.h    |  8 ++++
>   .../hwtracing/coresight/coresight-syscfg.c    | 37 +++++++++++++------
>   2 files changed, 34 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-config.h b/drivers/hwtracing/coresight/coresight-config.h
> index ae6295e308131..f04e73b91d9a6 100644
> --- a/drivers/hwtracing/coresight/coresight-config.h
> +++ b/drivers/hwtracing/coresight/coresight-config.h
> @@ -7,6 +7,7 @@
>   #ifndef _CORESIGHT_CORESIGHT_CONFIG_H
>   #define _CORESIGHT_CORESIGHT_CONFIG_H
>   
> +#include <linux/bits.h>
>   #include <linux/cleanup.h>
>   #include <linux/coresight.h>
>   #include <linux/types.h>
> @@ -30,6 +31,13 @@
>    */
>   #define CS_CFG_MATCH_CLASS_SRC_ALL	0x0001	/* match any source */
>   #define CS_CFG_MATCH_CLASS_SRC_ETM4	0x0002	/* match any ETMv4 device */
> +#define CS_CFG_MATCH_CLASS_MASK		GENMASK_U32(7, 0)
> +
> +/*
> + * flags defining device capabilities a feature can require. A feature loads on
> + * a device that matches one of its classes and has all of its capabilities.
> + */
> +#define CS_CFG_MATCH_CAP_MASK		GENMASK_U32(15, 8)
>   
>   /* flags defining device instance matching - used in config match desc data. */
>   #define CS_CFG_MATCH_INST_ANY		0x80000000 /* any instance of a class */
> diff --git a/drivers/hwtracing/coresight/coresight-syscfg.c b/drivers/hwtracing/coresight/coresight-syscfg.c
> index a816c22c87bc8..3ee104e94a4cd 100644
> --- a/drivers/hwtracing/coresight/coresight-syscfg.c
> +++ b/drivers/hwtracing/coresight/coresight-syscfg.c
> @@ -171,8 +171,22 @@ cscfg_alloc_csdev_feat(struct coresight_device *csdev, struct cscfg_feature_desc
>   	return feat_csdev;
>   }
>   
> -/* load one feature into one coresight device */
> +static bool cscfg_match_feat_csdev(u32 feat_flags, u32 csdev_flags)
> +{
> +	/* The device must be in one of the feature's classes */
> +	if (!(feat_flags & csdev_flags & CS_CFG_MATCH_CLASS_MASK))
> +		return false;
> +
> +	/* The device must have every capability the feature requires */
> +	if (feat_flags & ~csdev_flags & CS_CFG_MATCH_CAP_MASK)
> +		return false;
> +
> +	return true;
> +}
> +
> +/* Load the feature into the device if it matches, otherwise skip it. */
>   static int cscfg_load_feat_csdev(struct coresight_device *csdev,
> +				 u32 match_flags,
>   				 struct cscfg_feature_desc *feat_desc,
>   				 struct cscfg_csdev_feat_ops *ops)
>   {
> @@ -183,6 +197,9 @@ static int cscfg_load_feat_csdev(struct coresight_device *csdev,
>   	if (!ops->load_feat)
>   		return -EINVAL;
>   
> +	if (!cscfg_match_feat_csdev(feat_desc->match_flags, match_flags))
> +		return 0;
> +
>   	feat_csdev = cscfg_alloc_csdev_feat(csdev, feat_desc);
>   	if (!feat_csdev)
>   		return -ENOMEM;
> @@ -212,11 +229,11 @@ static int cscfg_add_feat_to_csdevs(struct cscfg_feature_desc *feat_desc)
>   	int err;
>   
>   	list_for_each_entry(csdev_item, &cscfg_mgr->csdev_desc_list, item) {
> -		if (csdev_item->match_flags & feat_desc->match_flags) {
> -			err = cscfg_load_feat_csdev(csdev_item->csdev, feat_desc, &csdev_item->ops);
> -			if (err)
> -				return err;
> -		}
> +		err = cscfg_load_feat_csdev(csdev_item->csdev,
> +					    csdev_item->match_flags, feat_desc,
> +					    &csdev_item->ops);
> +		if (err)
> +			return err;
>   	}
>   	return 0;
>   }
> @@ -739,11 +756,9 @@ static int cscfg_add_feats_csdev(struct coresight_device *csdev,
>   		return -EINVAL;
>   
>   	list_for_each_entry(feat_desc, &cscfg_mgr->feat_desc_list, item) {
> -		if (feat_desc->match_flags & match_flags) {
> -			err = cscfg_load_feat_csdev(csdev, feat_desc, ops);
> -			if (err)
> -				break;
> -		}
> +		err = cscfg_load_feat_csdev(csdev, match_flags, feat_desc, ops);
> +		if (err)
> +			break;
>   	}
>   	return err;
>   }

Reviewed-by: James Clark <james.clark@linaro.org>