Re: [PATCH v2 2/4] coresight: syscfg: Match feature capabilities separately from device class

[Leo Yan <leo.yan@arm.com>]

On Mon, Oct 12, 2026 at 04:05:21PM -0700, Amir Ayupov wrote:

[...]

> --- a/drivers/hwtracing/coresight/coresight-config.h
> +++ b/drivers/hwtracing/coresight/coresight-config.h
> @@ -30,6 +30,12 @@
>  #define CS_CFG_MATCH_CLASS_SRC_ALL	0x0001	/* match any source */
>  #define CS_CFG_MATCH_CLASS_SRC_ETM4	0x0002	/* match any ETMv4 device */

It is good to introduce a marco:

  #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		0x0000ff00

To make the mask explicitly 32-bit unsigned:

  #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 */

Not an issue with this patch, but CS_CFG_MATCH_INST_ANY appears to be
unused and could be removed in a separate cleanup patch.

> diff --git a/drivers/hwtracing/coresight/coresight-syscfg.c b/drivers/hwtracing/coresight/coresight-syscfg.c
> index a816c22c87bc8..1545d64afec01 100644
> --- a/drivers/hwtracing/coresight/coresight-syscfg.c
> +++ b/drivers/hwtracing/coresight/coresight-syscfg.c
> @@ -172,7 +172,21 @@ cscfg_alloc_csdev_feat(struct coresight_device *csdev, struct cscfg_feature_desc
>  }
>  
>  /* load one feature into one coresight device */
> +/*
> + * A feature matches a device that shares one of its class flags and has all of
> + * the capability flags it requires.
> + */
> +static bool cscfg_match_feat_csdev(u32 feat_flags, u32 csdev_flags)
> +{
> +	u32 caps = feat_flags & CS_CFG_MATCH_CAP_MASK;
> +
> +	return (feat_flags & csdev_flags & ~CS_CFG_MATCH_CAP_MASK) &&
> +	       (csdev_flags & caps) == caps;

For clearer comparison conditions:

       /* Class type must be matches */
       if ((feat_flags & CS_CFG_MATCH_CLASS_MASK) !=
           (csdev_flags & CS_CFG_MATCH_CLASS_MASK)
           return false;

       /* No required capabilities miss from the device */
       if (feat_flags & ~csdev_flags & CS_CFG_MATCH_CAP_MASK)
           return false;

       return true;

Thanks,
Leo