Re: [PATCH v2 3/4] coresight: etm4x: Report the external outputs the PMU counts

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

On 23/10/2026 15:00, Leo Yan wrote:
> On Fri, Oct 23, 2026 at 10:49:40AM +0100, James Clark wrote:
> 
> [...]
> 
>>>>     * a device that matches one of its classes and has all of its capabilities.
>>>>     */
>>>>    #define CS_CFG_MATCH_CAP_MASK		0x0000ff00
>>>> +/* trace unit external output n is countable by the PMU as TRCEXTOUTn */
>>>> +#define CS_CFG_MATCH_CAP_PMU_EXTOUT_SHIFT	8
>>>> +#define CS_CFG_MATCH_CAP_PMU_EXTOUT_NR	4	/* TRCEXTOUT0-3 */
>>>> +#define CS_CFG_MATCH_CAP_PMU_EXTOUT(n)	BIT(CS_CFG_MATCH_CAP_PMU_EXTOUT_SHIFT + (n))
>>
>> Isn't this recreating what GENMASK() and FIELD_PREP() does? Can we use that
>> instead?
> 
> TBC, are you suggesting using separate capability bits to represent
> TRCEXTOUT0-3? Why can't we use a single capability bit to indicate
> whether the feature is supported and caps->num_event to indicate
> the number of external output signals?

Just the pattern of *_SHIFT and other stuff to make a bitfield is 
usually better done with GENMASK(). Or if there are only 4 of them, even 
defining four BIT()s would be clearer.

But yes if a single bit and caps->num_event works we should do that instead.