Re: [PATCH v2] coresight: trbe: Hide enable_sink sysfs file

[Suzuki K Poulose <suzuki.poulose@arm.com>]

On 11/08/2026 10:10, James Clark wrote:
> 
> 
> On 11/08/2026 10:04, Leo Yan wrote:
>> On Fri, Aug 07, 2026 at 11:13:22AM +0100, James Clark wrote:
>>> TRBE doesn't support sysfs mode, but the enable_sink file can still be
>>> successfully written to enable the device, and only attempting to enable
>>> the source would later fail.
>>>
>>> Avoid misleading users by adding a flag that devices can use to hide
>>> either the enable_sink or enable_source files, and set it for TRBE.
>>>
>>> Don't set it for ETE as it's possible that ETE could appear on the
>>> legacy bus and work with sysfs, and writing to enable_source already
>>> reports EINVAL if the device doesn't support sysfs mode.
>>
>> It is a pity that we cannot determine from the ETE registers whether ETE
>> is connected to the legacy bus or TRBE.
>>
> 
> We could determine it from the device tree. A path has to be built or 
> you can't use it on the legacy bus either. Maybe we can do a more 
> general change in the future to hide the flag for any non-connected CPU 
> source.


There must be a sink enabled before the source can be enabled. So, 
enable_source will fail. I would leave things as is, given the
sinks can be loaded with modules and it is all dynamic

Cheers
Suzuki


> 
>>> Signed-off-by: James Clark <james.clark@linaro.org>
>>
>> Reviewed-by: Leo Yan <leo.yan@arm.com>
>