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Message-ID: <CAPDyKFqONKvPbtLRXKbF6x5RdNpJDCB1R0-7j-Epksva16Y_-Q@mail.gmail.com>
Date: Wed, 4 Feb 2026 15:21:15 +0100
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Josua Mayer <josua@...id-run.com>, Wolfram Sang <wsa+renesas@...g-engineering.com>
Cc: 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>,
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-can@...r.kernel.org>,
"linux-phy@...ts.infradead.org" <linux-phy@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>,
Dan Carpenter <dan.carpenter@...aro.org>
Subject: Re: [PATCH v8 2/7] mux: Add helper functions for getting optional and
selected mux-state
On Tue, 3 Feb 2026 at 16:35, Josua Mayer <josua@...id-run.com> wrote:
>
> On 03/02/2026 15:01, Josua Mayer 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 | 205 ++++++++++++++++++++++++++++++++++++-------
> > include/linux/mux/consumer.h | 108 ++++++++++++++++++++++-
> > 2 files changed, 278 insertions(+), 35 deletions(-)
> >
> > diff --git a/drivers/mux/core.c b/drivers/mux/core.c
> > index a3840fe0995f..2e8295e3aabe 100644
> > --- a/drivers/mux/core.c
> > +++ b/drivers/mux/core.c
> > @@ -46,6 +46,16 @@ static const struct class mux_class = {
> > .name = "mux",
> > };
> >
> > +/**
> > + * struct devm_mux_state_state - Tracks managed resources for mux-state objects.
> > + * @mstate: Pointer to a mux state.
> > + * @exit: An optional callback to execute before free.
> > + */
> > +struct devm_mux_state_state {
> > + struct mux_state *mstate;
> > + int (*exit)(struct mux_state *mstate);
> > +};
> > +
> > static DEFINE_IDA(mux_ida);
> >
> > static int __init mux_init(void)
> > @@ -516,17 +526,19 @@ static struct mux_chip *of_find_mux_chip_by_node(struct device_node *np)
> > return dev ? to_mux_chip(dev) : NULL;
> > }
> >
> > -/*
> > +/**
> > * mux_get() - Get the mux-control for a device.
> > * @dev: The device that needs a mux-control.
> > * @mux_name: The name identifying the mux-control.
> > * @state: Pointer to where the requested state is returned, or NULL when
> > * the required multiplexer states are handled by other means.
> > + * @optional: Whether to return NULL and silence errors when mux doesn't exist.
> > *
> > - * Return: A pointer to the mux-control, or an ERR_PTR with a negative errno.
> > + * Return: Pointer to the mux-control on success, an ERR_PTR with a negative errno on error,
> > + * or NULL if optional is true and mux doesn't exist.
> > */
> > static struct mux_control *mux_get(struct device *dev, const char *mux_name,
> > - unsigned int *state)
> > + unsigned int *state, bool optional)
> > {
> > struct device_node *np = dev->of_node;
> > struct of_phandle_args args;
> > @@ -542,7 +554,9 @@ static struct mux_control *mux_get(struct device *dev, const char *mux_name,
> > else
> > index = of_property_match_string(np, "mux-control-names",
> > mux_name);
> > - if (index < 0) {
> > + if (index < 0 && optional) {
> > + return NULL;
> > + } else if (index < 0) {
> > dev_err(dev, "mux controller '%s' not found\n",
> > mux_name);
> > return ERR_PTR(index);
> > @@ -558,8 +572,12 @@ static struct mux_control *mux_get(struct device *dev, const char *mux_name,
> > "mux-controls", "#mux-control-cells",
> > index, &args);
> > if (ret) {
> > + if (optional && ret == -ENOENT)
> > + return NULL;
> > +
> > dev_err(dev, "%pOF: failed to get mux-%s %s(%i)\n",
> > - np, state ? "state" : "control", mux_name ?: "", index);
> > + np, state ? "state" : "control",
> > + mux_name ?: "", index);
> > return ERR_PTR(ret);
> > }
> >
> > @@ -617,10 +635,28 @@ static struct mux_control *mux_get(struct device *dev, const char *mux_name,
> > */
> > struct mux_control *mux_control_get(struct device *dev, const char *mux_name)
> > {
> > - return mux_get(dev, mux_name, NULL);
> > + struct mux_control *mux = mux_get(dev, mux_name, NULL, false);
> > +
> > + if (!mux)
> > + return ERR_PTR(-ENOENT);
> > +
> > + return mux;
> > }
> > EXPORT_SYMBOL_GPL(mux_control_get);
> >
> > +/**
> > + * mux_control_get_optional() - Get the optional mux-control for a device.
> > + * @dev: The device that needs a mux-control.
> > + * @mux_name: The name identifying the mux-control.
> > + *
> > + * Return: A pointer to the mux-control, an ERR_PTR with a negative errno.
> * Return: Pointer to the mux-state on success, an ERR_PTR with a
> negative errno on error,
> * or NULL if mux doesn't exist.
>
> If there will be v9, I shall change this to be more precise similar to
> other functions.
The series looks good to me!
I can queue the series for v7.0 via my mmc tree and amend the change
according to above when applying, but I need the ack from Wolfram on
the i2c patch (patch5) first.
If this doesn't make it for v7.0, I suggest you re-spin a v9 after the
merge window.
Kind regards
Uffe
> > + */
> > +struct mux_control *mux_control_get_optional(struct device *dev, const char *mux_name)
> > +{
> > + return mux_get(dev, mux_name, NULL, true);
> > +}
> > +EXPORT_SYMBOL_GPL(mux_control_get_optional);
> > +
> > /**
> > * mux_control_put() - Put away the mux-control for good.
> > * @mux: The mux-control to put away.
> > @@ -657,10 +693,13 @@ struct mux_control *devm_mux_control_get(struct device *dev,
> > if (!ptr)
> > return ERR_PTR(-ENOMEM);
> >
> > - mux = mux_control_get(dev, mux_name);
> > + mux = mux_get(dev, mux_name, NULL, false);
> > if (IS_ERR(mux)) {
> > devres_free(ptr);
> > return mux;
> > + } else if (!mux) {
> > + devres_free(ptr);
> > + return ERR_PTR(-ENOENT);
> > }
> >
> > *ptr = mux;
> > @@ -670,14 +709,16 @@ struct mux_control *devm_mux_control_get(struct device *dev,
> > }
> > EXPORT_SYMBOL_GPL(devm_mux_control_get);
> >
> > -/*
> > +/**
> > * mux_state_get() - Get the mux-state for a device.
> > * @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.
> > *
> > - * Return: A pointer to the mux-state, or an ERR_PTR with a negative errno.
> > + * Return: Pointer to the mux-state on success, an ERR_PTR with a negative errno on error,
> > + * or NULL if optional is true and mux doesn't exist.
> > */
> > -static struct mux_state *mux_state_get(struct device *dev, const char *mux_name)
> > +static struct mux_state *mux_state_get(struct device *dev, const char *mux_name, bool optional)
> > {
> > struct mux_state *mstate;
> >
> ...
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