Re: [PATCH v3 1/3] PM: core: Rename module parameters prefix to "power"

[Rafael J. Wysocki]

On Tue, Jun 9, 2026 at 3:03 PM Tzung-Bi Shih <tzungbi@xxxxxxxxxx> wrote:
>
> On Tue, Jun 09, 2026 at 08:17:03PM +0900, Tomasz Figa wrote:
> > On Tue, Jun 9, 2026 at 8:10 PM Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote:
> > >
> > > On Tue, Jun 9, 2026 at 11:03 AM Tzung-Bi Shih <tzungbi@xxxxxxxxxx> wrote:
> > > >
> > > > On Mon, Jun 08, 2026 at 04:11:30PM +0200, Rafael J. Wysocki wrote:
> > > > > On Mon, Jun 8, 2026 at 4:16 AM Tzung-Bi Shih <tzungbi@xxxxxxxxxx> wrote:
> > > > > >
> > > > > > Currently, the module parameters defined in drivers/base/power/main.c
> > > > > > use the default prefix "main" (derived from the filename).  The prefix
> > > > > > "main" is too generic and non-descriptive for power management
> > > > > > parameters.
> > > > > >
> > > > > > Redefine MODULE_PARAM_PREFIX to "power." at the beginning of the file
> > > > > > to group the module parameters under the "power" namespace instead.
> > > > > > This makes the parameters more descriptive.
> > > > > >
> > > > > > Signed-off-by: Tzung-Bi Shih <tzungbi@xxxxxxxxxx>
> > > > > > ---
> > > > > > v3:
> > > > > > - No changes.
> > > > > >
> > > > > > v2: https://lore.kernel.org/all/20260604090756.2884671-2-tzungbi@xxxxxxxxxx
> > > > > > - New to the series.
> > > > > >
> > > > > > v1: Doesn't exist.
> > > > > >
> > > > > >  drivers/base/power/main.c | 3 +++
> > > > > >  1 file changed, 3 insertions(+)
> > > > > >
> > > > > > diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> > > > > > index ed48c292f575..cd864f3a2799 100644
> > > > > > --- a/drivers/base/power/main.c
> > > > > > +++ b/drivers/base/power/main.c
> > > > > > @@ -40,6 +40,9 @@
> > > > > >  #include "../base.h"
> > > > > >  #include "power.h"
> > > > > >
> > > > > > +#undef MODULE_PARAM_PREFIX
> > > > > > +#define MODULE_PARAM_PREFIX "power."
> > > > >
> > > > > "power" may be confused with the power supply support, so I'd rather
> > > > > use "pm" or even "pm_sleep" (in which case the "dpm_" prefix could be
> > > > > dropped from the new module param name in the next patch).
> > > >
> > > > Ack, will use "pm_sleep" in the next version.
> > > >
> > > > Regarding dropping the "dpm_" prefix, should this also apply to the existing
> > > > dpm_watchdog_all_cpu_backtrace parameter?  Or should we leave it as-is to
> > > > avoid breaking existing configurations?
> > >
> > > Breaking things for someone would be unfortunate.
> > >
> > > For consistency, let's retain the "dpm_watchdog" part in this name and
> > > use it in the new one.
> >
> > Hmm, doesn't the prefix change already break things?
>
> Theoretically yes, though it's worth noting that this parameter is
> relatively new.  It was introduced in v6.19 (Oct 2025) via commit
> a67818f74512 ("PM: dpm_watchdog: add module param to backtrace all CPUs").
>
> To my knowledge, the flag was originally introduced for ChromeOS [1], which
> doesn't actually rely on this module parameter in its production
> configuration yet [2].
>
> That said, I can't know the status of all other Linux distributions.  If we
> want to be 100% safe against breaking existing setups, retaining the "main"
> prefix is definitely the safest.
>
> Given its recent introduction and limited known usage, this might be the
> best window to rename the prefix before it gains wider adoption.
>
> What are your thoughts?

If somebody complains about it, we can reconsider, but using "main" as
a prefix for power management module parameters is definitely
confusing.

> [1] https://chromium-review.git.corp.google.com/c/chromiumos/third_party/kernel/+/7414781
> [2] https://chromium-review.git.corp.google.com/c/chromiumos/third_party/kernel/+/7414721