linux-kernel - Re: [PATCH] drivers/regulator: Notify sysfs about status changes

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Message-ID: <c2dd0533-3a60-4481-8621-86578e62aab6@sirena.org.uk>
Date:   Thu, 2 Nov 2023 15:01:34 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Naresh Solanki <naresh.solanki@...ements.com>
Cc:     zev@...ilderbeest.net, Liam Girdwood <lgirdwood@...il.com>,
        Patrick Rudolph <patrick.rudolph@...ements.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers/regulator: Notify sysfs about status changes

On Thu, Nov 02, 2023 at 08:17:35PM +0530, Naresh Solanki wrote:
> On Thu, 2 Nov 2023 at 18:36, Mark Brown <broonie@...nel.org> wrote:
> > On Thu, Nov 02, 2023 at 05:35:42PM +0530, Naresh Solanki wrote:

> > > > We probably should filter the events more, there's events for pre and
> > > > post voltage change for example which aren't status changes so would be
> > > > spurious.  It ought not to break anything but we should still avoid
> > > > unneeded work.

> > > Can you please provide me inputs on the additional filtering needed for this.
> > > Like some list of events for notify on status?

> > I think I'd start off with just reporting things that are obviously
> > errors and not things that should ever go off during normal operation.

> This is what I could come up with:
>         if (event & REGULATOR_EVENT_VOLTAGE_CHANGE) {
>                 name = dev_attr_microvolts.attr.name;
>                 sysfs_notify(&rdev->dev.kobj, NULL, name);
>         } else if (event & (REGULATOR_EVENT_DISABLE | REGULATOR_EVENT_ENABLE)){
>                 name = dev_attr_status.attr.name;
>                 sysfs_notify(&rdev->dev.kobj, NULL, name);
>         }

That's the opposite sense to what I was thinking of - we're reporting
voltage changes and enables to userspace rather than just errors.  My
concern here is that this could generate an awful lot of notificaitons
for normal operation on systems that don't use the uevents, I was
expecting this to be used for errors.  Could you remind me what the use
case is here, I think I might've got myself confused sorry?

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