Re: [PATCH] coresight replicator: set default y after Kconfig rename

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

On 08/02/18 17:22, Kim Phillips wrote:
> On Thu, 8 Feb 2018 08:59:30 -0700
> Mathieu Poirier <mathieu.poirier@linaro.org> wrote:
> 
>> On 7 February 2018 at 14:03, Kim Phillips <kim.phillips@arm.com> wrote:
>>> Commit 1c8859848dbb ("coresight replicator: Cleanup programmable
>>> replicator naming") changed the Kconfig symbol name from
>>> QCOM_REPLICATOR, which, whilst not in the single arm64 defconfig,
>>> was being set in my juno build script, which left the new symbol unset,
>>> causing the following unexpected grief:
>>>
>>>   # ./perf record -vvv -C 0 -e cs_etm/@20070000.etr/ --per-thread true
>>>   ..<snip>..
>>>   sys_perf_event_open: pid -1  cpu 0  group_fd -1  flags 0x8 = 5
>>>   mmap size 528384B
>>>   AUX area mmap length 4194304
>>>   perf event ring buffer mmapped per cpu
>>>   failed to mmap AUX area
>>>   failed to mmap with 12 (Cannot allocate memory)
>>>
>>> Make it default y to help not surprise unsuspecting users.
>>>
>>> Fixes: 1c8859848dbb ("coresight replicator: Cleanup programmable replicator naming")
>>> Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
>>> Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
>>> Signed-off-by: Kim Phillips <kim.phillips@arm.com>
>>> ---
>>>   drivers/hwtracing/coresight/Kconfig | 1 +
>>>   1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/hwtracing/coresight/Kconfig b/drivers/hwtracing/coresight/Kconfig
>>> index ef9cb3c164e1..b94bbd95efa6 100644
>>> --- a/drivers/hwtracing/coresight/Kconfig
>>> +++ b/drivers/hwtracing/coresight/Kconfig
>>> @@ -73,6 +73,7 @@ config CORESIGHT_SOURCE_ETM4X
>>>   config CORESIGHT_DYNAMIC_REPLICATOR
>>>          bool "CoreSight Programmable Replicator driver"
>>>          depends on CORESIGHT_LINKS_AND_SINKS
>>> +       default y
>>>          help
>>>            This enables support for dynamic CoreSight replicator link driver.
>>>            The programmable ATB replicator allows independent filtering of the
>>
>> As I said before don't see why it needs to be treated differently than other CS
>> blocks
> 
> I don't think it does either, but this one is special since it recently
> underwent a rename, which breaks its users that were setting the old
> name in their config builds.  The default y keeps it set in those
> cases, thereby discontinuing any such regression.

I don't think the kernel CONFIG symbols are part of the kernel ABI. So,
unfortunately the users have to take care of making sure they select what
they need.

Suzuki