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Message-ID: <CAMuHMdXgLR9yeLa5JKNdAOtNEirJ8263bmn1zRNAnKnmf8F-Sg@mail.gmail.com>
Date: Thu, 29 Jan 2026 17:13:10 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Ulf Hansson <ulf.hansson@...aro.org>
Cc: Josua Mayer <josua@...id-run.com>, Marc Kleine-Budde <mkl@...gutronix.de>,
Vincent Mailhol <mailhol@...nel.org>, Vinod Koul <vkoul@...nel.org>,
Neil Armstrong <neil.armstrong@...aro.org>, Peter Rosin <peda@...ntia.se>,
Aaro Koskinen <aaro.koskinen@....fi>, Andreas Kemnade <andreas@...nade.info>,
Kevin Hilman <khilman@...libre.com>, Roger Quadros <rogerq@...nel.org>,
Tony Lindgren <tony@...mide.com>, Janusz Krzysztofik <jmkrzyszt@...il.com>, Vignesh R <vigneshr@...com>,
Andi Shyti <andi.shyti@...nel.org>, Rob Herring <robh@...nel.org>,
Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>,
Geert Uytterhoeven <geert+renesas@...der.be>, Magnus Damm <magnus.damm@...il.com>,
Wolfram Sang <wsa+renesas@...g-engineering.com>,
Yazan Shhady <yazan.shhady@...id-run.com>, Jon Nettleton <jon@...id-run.com>,
Mikhail Anikin <mikhail.anikin@...id-run.com>, linux-can@...r.kernel.org,
linux-phy@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux-omap@...r.kernel.org, linux-i2c@...r.kernel.org,
linux-mmc@...r.kernel.org, devicetree@...r.kernel.org,
linux-renesas-soc@...r.kernel.org, Dan Carpenter <dan.carpenter@...aro.org>
Subject: Re: [PATCH v7 2/7] mux: Add helper functions for getting optional and
selected mux-state
On Thu, 29 Jan 2026 at 17:06, Ulf Hansson <ulf.hansson@...aro.org> wrote:
> On Wed, 28 Jan 2026 at 15:46, Josua Mayer <josua@...id-run.com> wrote:
> >
> > In-tree phy-can-transceiver driver has already implemented a local
> > version of devm_mux_state_get_optional.
> >
> > The omap-i2c driver gets and selects an optional mux in its probe
> > function without using any helper.
> >
> > Add new helper functions covering both aforementioned use-cases:
> >
> > - mux_control_get_optional:
> > Get a mux-control if specified in dt, return NULL otherwise.
> > - devm_mux_state_get_optional:
> > Get a mux-state if specified in dt, return NULL otherwise.
> > - devm_mux_state_get_selected:
> > Get and select a mux-state specified in dt, return error otherwise.
> > - devm_mux_state_get_optional_selected:
> > Get and select a mux-state if specified in dt, return error or NULL.
> >
> > Existing mux_get helper function is changed to take an extra argument
> > indicating whether the mux is optional.
> > In this case no error is printed, and NULL returned in case of ENOENT.
> >
> > Calling code is adapted to handle NULL return case, and to pass optional
> > argument as required.
> >
> > To support automatic deselect for _selected helper, a new structure is
> > created storing an exit pointer similar to clock core which is called on
> > release.
> >
> > To facilitate code sharing between optional/mandatory/selected helpers,
> > a new internal helper function is added to handle quiet (optional) and
> > verbose (mandatory) errors, as well as storing the correct callback for
> > devm release: __devm_mux_state_get
> >
> > Due to this structure devm_mux_state_get_*_selected can no longer print
> > a useful error message when select fails. Instead callers should print
> > errors where needed.
> >
> > Commit e153fdea9db04 ("phy: can-transceiver: Re-instate "mux-states"
> > property presence check") noted that "mux_get() always prints an error
> > message in case of an error, including when the property is not present,
> > confusing the user."
> >
> > The first error message covers the case that a mux name is not matched
> > in dt. The second error message is based on of_parse_phandle_with_args
> > return value.
> >
> > In optional case no error is printed and NULL is returned.
> > This ensures that the new helper functions will not confuse the user
> > either.
> >
> > With the addition of optional helper functions it became clear that
> > drivers should compile and link even if CONFIG_MULTIPLEXER was not enabled.
> > Add stubs for all symbols exported by mux core.
> >
> > Signed-off-by: Josua Mayer <josua@...id-run.com>
> > ---
> > drivers/mux/core.c | 178 ++++++++++++++++++++++++++++++++++++-------
> > include/linux/mux/consumer.h | 108 +++++++++++++++++++++++++-
> > 2 files changed, 253 insertions(+), 33 deletions(-)
> >
> > diff --git a/drivers/mux/core.c b/drivers/mux/core.c
> > index a3840fe0995f..b01ec126caaf 100644
> > --- a/drivers/mux/core.c
> > +++ b/drivers/mux/core.c
>
> [...]
>
> > static void devm_mux_state_release(struct device *dev, void *res)
> > {
> > - struct mux_state *mstate = *(struct mux_state **)res;
> > + struct devm_mux_state_state *devm_state = res;
> >
> > - mux_state_put(mstate);
> > + if (devm_state->exit)
> > + devm_state->exit(devm_state->mstate);
> > +
> > + mux_state_put(devm_state->mstate);
> > }
> >
> > /**
> > - * devm_mux_state_get() - Get the mux-state for a device, with resource
> > - * management.
> > - * @dev: The device that needs a mux-control.
> > - * @mux_name: The name identifying the mux-control.
> > + * __devm_mux_state_get() - Get the optional mux-state for a device,
> > + * with resource management.
> > + * @dev: The device that needs a mux-state.
> > + * @mux_name: The name identifying the mux-state.
> > + * @optional: Whether to return NULL and silence errors when mux doesn't exist.
> > + * @init: Optional function pointer for mux-state object initialisation.
> > + * @exit: Optional function pointer for mux-state object cleanup on release.
> > *
> > * Return: Pointer to the mux-state, or an ERR_PTR with a negative errno.
> > */
> > -struct mux_state *devm_mux_state_get(struct device *dev,
> > - const char *mux_name)
> > +static struct mux_state *__devm_mux_state_get(struct device *dev, const char *mux_name,
> > + bool optional,
> > + int (*init)(struct mux_state *mstate),
> > + int (*exit)(struct mux_state *mstate))
> > {
> > - struct mux_state **ptr, *mstate;
> > + struct devm_mux_state_state *devm_state;
> > + struct mux_state *mstate;
> > + int ret;
> >
> > - ptr = devres_alloc(devm_mux_state_release, sizeof(*ptr), GFP_KERNEL);
> > - if (!ptr)
> > + devm_state = devres_alloc(devm_mux_state_release, sizeof(*devm_state), GFP_KERNEL);
> > + if (!devm_state)
> > return ERR_PTR(-ENOMEM);
> >
> > - mstate = mux_state_get(dev, mux_name);
> > - if (IS_ERR(mstate)) {
> > - devres_free(ptr);
> > - return mstate;
> > + mstate = mux_state_get(dev, mux_name, optional);
> > + if (IS_ERR_OR_NULL(mstate)) {
> > + ret = PTR_ERR(mstate);
>
> Should this be PTR_ERR_OR_ZERO?
"mux_state_get() never returns NULL"
https://lore.kernel.org/202601221036.J0kR78Uw-lkp@intel.com
>
> > + goto err_mux_state_get;
> > }
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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