lkml.org 
[lkml]   [2018]   [Jul]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [RFC V4 0/3] arm_pmu: acpi: variant support and QCOM Falkor extensions
Hi Will,

On Fri, Jul 13, 2018 at 10:33 AM, Will Deacon <will.deacon@arm.com> wrote:

[snip]

> I'm mostly ok with this approach, but I have a concern with the way in which
> the sysfs interface for carving up the config fields is implemented. If this
> is intended to be a strict extension to the armv8 pmu architecture, then I
> don't think you should be overriding the attr_groups entirely. Rather, you
> should be taking the attr_groups from pmuv3 and then extending them in a way
> which avoids overlapping field allocations by construction.
>
> As it stands, you already have an overlap between the pcc bit and the
> chained counter bit which Suzuki has implemented and it will be very easy to
> introduce API breakage if we don't enforce this as part of the design.
>
> Will

FYI, I left Qualcomm on July 6, one of my former colleagues will submit
new iterations of this series. I will continue to comment on this and future
patchsets as a courtesy to my former colleagues and the community.

Thanks for pointing out the sysfs issue. My suggestion on how to address it is:

1. Reserve config and config1 for architectural format attributes and
config2 for extension format attributes.
2. Add a struct attribute ** parameter to the extension init function so
extensions can return the new attributes.
3. The extension framework code in arm_pmu_acpi.c can then allocate a new
attribute array to contain the base and extension attributes and ensure
all the new attributes are on config2.

Though a more elaborate approach can be implemented to find conflicts in
bit usage within config fields, it would require much more code for a
relatively simple problem. Thoughts?

Thanks,
Agustín

\
 
 \ /
  Last update: 2018-07-15 22:36    [W:0.939 / U:0.352 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site