[PATCH v7 0/7] mmc: host: renesas_sdhi_core: support configuring an optional sdio mux

[PATCH v7 0/7] mmc: host: renesas_sdhi_core: support configuring an optional sdio mux

[Josua Mayer]

Some Renesas SoC based boards mux SD and eMMC on a single sdio
controller, exposing user control by dip switch and software control by
gpio.

Purpose is to simplify development and provisioning by selecting boot
media at power-on, and again before starting linux.

Add binding and driver support for linking a (gpio) mux to renesas sdio
controller.

Introduce generic helper functions for getting managed and selected
mux-state objects, and switch i2c-omap and phy-can-transceiver drivers.

Signed-off-by: Josua Mayer <josua@solid-run.com>
---
Changes in v7:
- picked up reviewed-tags
- fix Kconfig change to add the missing prompt for CONFIG_MULTIPLEXER,
  and enable it by default when COMPILE_TEST is set.
  (Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>)
- fix another kernel build robot warning: undocumented C struct member
- Link to v6: https://lore.kernel.org/r/20260121-rz-sdio-mux-v6-0-38aa39527928@solid-run.com

Changes in v6:
- replaced /* with /** for devm_mux_state_state function description.
- collected review tags.
- fixed checkpatch warnings (space-before-tab, void-return).
  (Reported-by: Geert Uytterhoeven)
- fixed use-after-free in mux core mux_get function.
  (Reported-by: Geert Uytterhoeven)
- fix mux helper error path uninitialised return code variable.
  (Reported-by: kernel test robot <lkp@intel.com>)
- Link to v5: https://lore.kernel.org/r/20260118-rz-sdio-mux-v5-0-3c37e8872683@solid-run.com

Changes in v5:
- implemented automatic mux deselect for devm_*_selected.
  (Reported-by: Wolfram Sang <wsa+renesas@sang-engineering.com>)
- because of semantic changes I dropped reviewed and acks from omap-i2c
  patch (Andreas Kemnade / Wolfram Sang).
- fix invalid return value in void function for mux helper stubs
  (Reported-by: kernel test robot <lkp@intel.com>)
- Link to v4: https://lore.kernel.org/r/20251229-rz-sdio-mux-v4-0-a023e55758fe@solid-run.com

Changes in v4:
- added MULTIPLEXER Kconfig help text.
- removed "select MULTIPLEXER" from renesas sdhi Kconfig, as it is
  not required for all devices using this driver.
- added stubs for all symbols exported by mux core.
  (Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>)
- refactored mux core logic to silence ENOENT errors only on optional
  code paths, keeping error printing unchanged otherwise.
  (Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>)
- picked up various reviewed- and acked-by tags
- Link to v3: https://lore.kernel.org/r/20251210-rz-sdio-mux-v3-0-ca628db56d60@solid-run.com

Changes in v3:
- updated omap-i2c and phy-can-transceiver to use new helpers.
- created generic helper functions for getting managed optional mux-state.
  (Reported-by: Rob Herring <robh@kernel.org>)
- picked up binding ack by Rob Herring.
- replaced use of "SDIO" with "SD/SDIO/eMMC" in binding document and
  commit descriptions.
  (Reported-by: Ulf Hansson <ulf.hansson@linaro.org>)
- Link to v2: https://lore.kernel.org/r/20251201-rz-sdio-mux-v2-0-bcb581b88dd7@solid-run.com

Changes in v2:
- dropped mux-controller node from dt binding example
  (Reported-by: Conor Dooley <conor@kernel.org>
   Reported-by: Krzysztof Kozlowski <krzk@kernel.org>)
- Link to v1: https://lore.kernel.org/r/20251128-rz-sdio-mux-v1-0-1ede318d160f@solid-run.com

---
Josua Mayer (7):
      phy: can-transceiver: rename temporary helper function to avoid conflict
      mux: Add helper functions for getting optional and selected mux-state
      mux: add help text for MULTIPLEXER config option
      phy: can-transceiver: drop temporary helper getting optional mux-state
      i2c: omap: switch to new generic helper for getting selected mux-state
      dt-bindings: mmc: renesas,sdhi: Add mux-states property
      mmc: host: renesas_sdhi_core: support selecting an optional mux

 .../devicetree/bindings/mmc/renesas,sdhi.yaml      |   6 +
 drivers/i2c/busses/i2c-omap.c                      |  24 +--
 drivers/mmc/host/renesas_sdhi_core.c               |   6 +
 drivers/mux/Kconfig                                |   8 +-
 drivers/mux/core.c                                 | 178 +++++++++++++++++----
 drivers/phy/phy-can-transceiver.c                  |  10 --
 include/linux/mux/consumer.h                       | 108 ++++++++++++-
 7 files changed, 277 insertions(+), 63 deletions(-)
---
base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8
change-id: 20251128-rz-sdio-mux-acc5137f1618

Best regards,
-- 
Josua Mayer <josua@solid-run.com>

[PATCH v7 1/7] phy: can-transceiver: rename temporary helper function to avoid conflict

[Josua Mayer]

Rename the temporary devm_mux_state_get_optional function to avoid
conflict with upcoming implementation in multiplexer subsystem.

Acked-by: Vinod Koul <vkoul@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Josua Mayer <josua@solid-run.com>
---
 drivers/phy/phy-can-transceiver.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/phy/phy-can-transceiver.c b/drivers/phy/phy-can-transceiver.c
index 330356706ad7..81591d247128 100644
--- a/drivers/phy/phy-can-transceiver.c
+++ b/drivers/phy/phy-can-transceiver.c
@@ -128,7 +128,7 @@ MODULE_DEVICE_TABLE(of, can_transceiver_phy_ids);
 
 /* Temporary wrapper until the multiplexer subsystem supports optional muxes */
 static inline struct mux_state *
-devm_mux_state_get_optional(struct device *dev, const char *mux_name)
+temp_devm_mux_state_get_optional(struct device *dev, const char *mux_name)
 {
 	if (!of_property_present(dev->of_node, "mux-states"))
 		return NULL;
@@ -183,7 +183,7 @@ static int can_transceiver_phy_probe(struct platform_device *pdev)
 	priv->num_ch = num_ch;
 	platform_set_drvdata(pdev, priv);
 
-	mux_state = devm_mux_state_get_optional(dev, NULL);
+	mux_state = temp_devm_mux_state_get_optional(dev, NULL);
 	if (IS_ERR(mux_state))
 		return PTR_ERR(mux_state);
 

-- 
2.43.0

[PATCH v7 2/7] mux: Add helper functions for getting optional and selected mux-state

[Josua Mayer]

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@solid-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
@@ -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 execte 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)
@@ -522,11 +532,12 @@ static struct mux_chip *of_find_mux_chip_by_node(struct device_node *np)
  * @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.
  */
 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 +553,9 @@ 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 +571,12 @@ 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 +634,23 @@ 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);
+	return mux_get(dev, mux_name, NULL, false);
 }
 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.
+ */
+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.
@@ -657,8 +687,8 @@ struct mux_control *devm_mux_control_get(struct device *dev,
 	if (!ptr)
 		return ERR_PTR(-ENOMEM);
 
-	mux = mux_control_get(dev, mux_name);
-	if (IS_ERR(mux)) {
+	mux = mux_get(dev, mux_name, NULL, false);
+	if (IS_ERR_OR_NULL(mux)) {
 		devres_free(ptr);
 		return mux;
 	}
@@ -677,20 +707,19 @@ EXPORT_SYMBOL_GPL(devm_mux_control_get);
  *
  * Return: A pointer to the mux-state, or an ERR_PTR with a negative errno.
  */
-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;
+	struct mux_control *mux;
 
 	mstate = kzalloc(sizeof(*mstate), GFP_KERNEL);
 	if (!mstate)
 		return ERR_PTR(-ENOMEM);
 
-	mstate->mux = mux_get(dev, mux_name, &mstate->state);
-	if (IS_ERR(mstate->mux)) {
-		int err = PTR_ERR(mstate->mux);
-
+	mstate->mux = mux = mux_get(dev, mux_name, &mstate->state, optional);
+	if (IS_ERR_OR_NULL(mux)) {
 		kfree(mstate);
-		return ERR_PTR(err);
+		return ERR_CAST(mux);
 	}
 
 	return mstate;
@@ -710,41 +739,132 @@ static void mux_state_put(struct mux_state *mstate)
 
 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);
+		goto err_mux_state_get;
 	}
 
-	*ptr = mstate;
-	devres_add(dev, ptr);
+	if (init) {
+		ret = init(mstate);
+		if (ret)
+			goto err_mux_state_init;
+	}
+
+	devm_state->mstate = mstate;
+	devm_state->exit = exit;
+	devres_add(dev, devm_state);
 
 	return mstate;
+
+err_mux_state_init:
+	mux_state_put(mstate);
+err_mux_state_get:
+	devres_free(devm_state);
+	return ERR_PTR(ret);
+}
+
+/**
+ * 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.
+ *
+ * Return: Pointer to the mux-state, or an ERR_PTR with a negative errno.
+ *
+ * The mux-state will automatically be freed on release.
+ */
+struct mux_state *devm_mux_state_get(struct device *dev, const char *mux_name)
+{
+	return __devm_mux_state_get(dev, mux_name, false, NULL, NULL);
 }
 EXPORT_SYMBOL_GPL(devm_mux_state_get);
 
+/**
+ * devm_mux_state_get_optional() - 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.
+ *
+ * Return: Pointer to the mux-state, or an ERR_PTR with a negative errno.
+ *
+ * The mux-state will automatically be freed on release.
+ */
+struct mux_state *devm_mux_state_get_optional(struct device *dev, const char *mux_name)
+{
+	return __devm_mux_state_get(dev, mux_name, true, NULL, NULL);
+}
+EXPORT_SYMBOL_GPL(devm_mux_state_get_optional);
+
+/**
+ * devm_mux_state_get_selected() - Get the mux-state for a device, with
+ *				   resource management.
+ * @dev: The device that needs a mux-state.
+ * @mux_name: The name identifying the mux-state.
+ *
+ * Return: Pointer to the mux-state, or an ERR_PTR with a negative errno.
+ *
+ * The returned mux-state (if valid) is already selected.
+ *
+ * The mux-state will automatically be deselected and freed on release.
+ */
+struct mux_state *devm_mux_state_get_selected(struct device *dev, const char *mux_name)
+{
+	return __devm_mux_state_get(dev, mux_name, false, mux_state_select, mux_state_deselect);
+}
+EXPORT_SYMBOL_GPL(devm_mux_state_get_selected);
+
+/**
+ * devm_mux_state_get_optional_selected() - 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.
+ *
+ * Return: Pointer to the mux-state, or an ERR_PTR with a negative errno.
+ *
+ * The returned mux-state (if valid) is already selected.
+ *
+ * The mux-state will automatically be deselected and freed on release.
+ */
+struct mux_state *devm_mux_state_get_optional_selected(struct device *dev,
+						       const char *mux_name)
+{
+	return __devm_mux_state_get(dev, mux_name, true, mux_state_select, mux_state_deselect);
+}
+EXPORT_SYMBOL_GPL(devm_mux_state_get_optional_selected);
+
 /*
  * Using subsys_initcall instead of module_init here to try to ensure - for
  * the non-modular case - that the subsystem is initialized when mux consumers
diff --git a/include/linux/mux/consumer.h b/include/linux/mux/consumer.h
index 2e25c838f831..3ede55b907eb 100644
--- a/include/linux/mux/consumer.h
+++ b/include/linux/mux/consumer.h
@@ -16,6 +16,8 @@ struct device;
 struct mux_control;
 struct mux_state;
 
+#ifdef CONFIG_MULTIPLEXER
+
 unsigned int mux_control_states(struct mux_control *mux);
 int __must_check mux_control_select_delay(struct mux_control *mux,
 					  unsigned int state,
@@ -54,11 +56,109 @@ int mux_control_deselect(struct mux_control *mux);
 int mux_state_deselect(struct mux_state *mstate);
 
 struct mux_control *mux_control_get(struct device *dev, const char *mux_name);
+struct mux_control *mux_control_get_optional(struct device *dev, const char *mux_name);
 void mux_control_put(struct mux_control *mux);
 
-struct mux_control *devm_mux_control_get(struct device *dev,
-					 const char *mux_name);
-struct mux_state *devm_mux_state_get(struct device *dev,
-				     const char *mux_name);
+struct mux_control *devm_mux_control_get(struct device *dev, const char *mux_name);
+struct mux_state *devm_mux_state_get(struct device *dev, const char *mux_name);
+struct mux_state *devm_mux_state_get_optional(struct device *dev, const char *mux_name);
+struct mux_state *devm_mux_state_get_selected(struct device *dev, const char *mux_name);
+struct mux_state *devm_mux_state_get_optional_selected(struct device *dev, const char *mux_name);
+
+#else
+
+static inline unsigned int mux_control_states(struct mux_control *mux)
+{
+	return 0;
+}
+static inline int __must_check mux_control_select_delay(struct mux_control *mux,
+							unsigned int state, unsigned int delay_us)
+{
+	return -EOPNOTSUPP;
+}
+static inline int __must_check mux_state_select_delay(struct mux_state *mstate,
+						      unsigned int delay_us)
+{
+	return -EOPNOTSUPP;
+}
+static inline int __must_check mux_control_try_select_delay(struct mux_control *mux,
+							    unsigned int state,
+							    unsigned int delay_us)
+{
+	return -EOPNOTSUPP;
+}
+static inline int __must_check mux_state_try_select_delay(struct mux_state *mstate,
+							  unsigned int delay_us)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int __must_check mux_control_select(struct mux_control *mux,
+						  unsigned int state)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int __must_check mux_state_select(struct mux_state *mstate)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int __must_check mux_control_try_select(struct mux_control *mux,
+						      unsigned int state)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int __must_check mux_state_try_select(struct mux_state *mstate)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int mux_control_deselect(struct mux_control *mux)
+{
+	return -EOPNOTSUPP;
+}
+static inline int mux_state_deselect(struct mux_state *mstate)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline struct mux_control *mux_control_get(struct device *dev, const char *mux_name)
+{
+	return ERR_PTR(-EOPNOTSUPP);
+}
+static inline struct mux_control *mux_control_get_optional(struct device *dev,
+							   const char *mux_name)
+{
+	return NULL;
+}
+static inline void mux_control_put(struct mux_control *mux) {}
+
+static inline struct mux_control *devm_mux_control_get(struct device *dev, const char *mux_name)
+{
+	return ERR_PTR(-EOPNOTSUPP);
+}
+static inline struct mux_state *devm_mux_state_get(struct device *dev, const char *mux_name)
+{
+	return ERR_PTR(-EOPNOTSUPP);
+}
+static inline struct mux_state *devm_mux_state_get_optional(struct device *dev,
+							    const char *mux_name)
+{
+	return NULL;
+}
+static inline struct mux_state *devm_mux_state_get_selected(struct device *dev,
+							    const char *mux_name)
+{
+	return ERR_PTR(-EOPNOTSUPP);
+}
+static inline struct mux_state *devm_mux_state_get_optional_selected(struct device *dev,
+								     const char *mux_name)
+{
+	return NULL;
+}
+
+#endif /* CONFIG_MULTIPLEXER */
 
 #endif /* _LINUX_MUX_CONSUMER_H */

-- 
2.43.0

[PATCH v7 3/7] mux: add help text for MULTIPLEXER config option

[Josua Mayer]

Add prompt and help text for CONFIG_MULTIPLEXER to allow enabling this
option thorugh the kernel configuration without explicit "select" driver
dependencies.

Select it by default when COMPILE_TEST is set for better coverage.

Signed-off-by: Josua Mayer <josua@solid-run.com>
---
 drivers/mux/Kconfig | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/mux/Kconfig b/drivers/mux/Kconfig
index c68132e38138..e31c46820bdf 100644
--- a/drivers/mux/Kconfig
+++ b/drivers/mux/Kconfig
@@ -4,7 +4,13 @@
 #
 
 config MULTIPLEXER
-	tristate
+	tristate "Generic Multiplexer Support" if COMPILE_TEST
+	help
+	  This framework is designed to abstract multiplexer handling for
+	  devices via various GPIO-, MMIO/Regmap or specific multiplexer
+	  controller chips.
+
+	  If unsure, say no.
 
 menu "Multiplexer drivers"
 	depends on MULTIPLEXER

-- 
2.43.0

[PATCH v7 4/7] phy: can-transceiver: drop temporary helper getting optional mux-state

[Josua Mayer]

Multiplexer subsystem has now added helpers for getting managed optional
mux-state.

Switch to the new devm_mux_state_get_optional helper.

This change is only compile-tested.

Acked-by: Vinod Koul <vkoul@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Josua Mayer <josua@solid-run.com>
---
 drivers/phy/phy-can-transceiver.c | 12 +-----------
 1 file changed, 1 insertion(+), 11 deletions(-)

diff --git a/drivers/phy/phy-can-transceiver.c b/drivers/phy/phy-can-transceiver.c
index 81591d247128..2b52e47f247a 100644
--- a/drivers/phy/phy-can-transceiver.c
+++ b/drivers/phy/phy-can-transceiver.c
@@ -126,16 +126,6 @@ static const struct of_device_id can_transceiver_phy_ids[] = {
 };
 MODULE_DEVICE_TABLE(of, can_transceiver_phy_ids);
 
-/* Temporary wrapper until the multiplexer subsystem supports optional muxes */
-static inline struct mux_state *
-temp_devm_mux_state_get_optional(struct device *dev, const char *mux_name)
-{
-	if (!of_property_present(dev->of_node, "mux-states"))
-		return NULL;
-
-	return devm_mux_state_get(dev, mux_name);
-}
-
 static struct phy *can_transceiver_phy_xlate(struct device *dev,
 					     const struct of_phandle_args *args)
 {
@@ -183,7 +173,7 @@ static int can_transceiver_phy_probe(struct platform_device *pdev)
 	priv->num_ch = num_ch;
 	platform_set_drvdata(pdev, priv);
 
-	mux_state = temp_devm_mux_state_get_optional(dev, NULL);
+	mux_state = devm_mux_state_get_optional(dev, NULL);
 	if (IS_ERR(mux_state))
 		return PTR_ERR(mux_state);
 

-- 
2.43.0

[PATCH v7 5/7] i2c: omap: switch to new generic helper for getting selected mux-state

[Josua Mayer]

Multiplexer subsystem has added generic helper functions for getting an
already selected mux-state object.

Replace existing logic in probe with the equivalent helper function.

There is a functional difference in that the mux is now automatically
deselected on release, replacing the explicit mux_state_deselect call.

This change is only compile-tested.

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Andreas Kemnade <andreas@kemnade.info>
Signed-off-by: Josua Mayer <josua@solid-run.com>
---
 drivers/i2c/busses/i2c-omap.c | 24 +++++-------------------
 1 file changed, 5 insertions(+), 19 deletions(-)

diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
index d9f590f0c384..f02d294db42a 100644
--- a/drivers/i2c/busses/i2c-omap.c
+++ b/drivers/i2c/busses/i2c-omap.c
@@ -1453,27 +1453,16 @@ omap_i2c_probe(struct platform_device *pdev)
 				       (1000 * omap->speed / 8);
 	}
 
-	if (of_property_present(node, "mux-states")) {
-		struct mux_state *mux_state;
-
-		mux_state = devm_mux_state_get(&pdev->dev, NULL);
-		if (IS_ERR(mux_state)) {
-			r = PTR_ERR(mux_state);
-			dev_dbg(&pdev->dev, "failed to get I2C mux: %d\n", r);
-			goto err_put_pm;
-		}
-		omap->mux_state = mux_state;
-		r = mux_state_select(omap->mux_state);
-		if (r) {
-			dev_err(&pdev->dev, "failed to select I2C mux: %d\n", r);
-			goto err_put_pm;
-		}
+	omap->mux_state = devm_mux_state_get_optional_selected(&pdev->dev, NULL);
+	if (IS_ERR(omap->mux_state)) {
+		r = PTR_ERR(omap->mux_state);
+		goto err_put_pm;
 	}
 
 	/* reset ASAP, clearing any IRQs */
 	r = omap_i2c_init(omap);
 	if (r)
-		goto err_mux_state_deselect;
+		goto err_put_pm;
 
 	if (omap->rev < OMAP_I2C_OMAP1_REV_2)
 		r = devm_request_irq(&pdev->dev, omap->irq, omap_i2c_omap1_isr,
@@ -1515,9 +1504,6 @@ omap_i2c_probe(struct platform_device *pdev)
 
 err_unuse_clocks:
 	omap_i2c_write_reg(omap, OMAP_I2C_CON_REG, 0);
-err_mux_state_deselect:
-	if (omap->mux_state)
-		mux_state_deselect(omap->mux_state);
 err_put_pm:
 	pm_runtime_put_sync(omap->dev);
 err_disable_pm:

-- 
2.43.0

[PATCH v7 6/7] dt-bindings: mmc: renesas,sdhi: Add mux-states property

[Josua Mayer]

Add mux controller support for data or control lines that are muxed
between a host and multiple cards.

There are several devices supporting a choice of eMMC or SD on a single
board by both dip switch and gpio, e.g. Renesas RZ/G2L SMARC SoM and
SolidRun RZ/G2L SoM.

In-tree dts for the Renesas boards currently rely on preprocessor macros
and gpio hogs to describe the respective cards.

By adding mux-states property to sdhi controller description, boards can
correctly describe the mux that already exists in hardware - and drivers
can coordinate between mux selection and probing for cards.

Acked-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Josua Mayer <josua@solid-run.com>
---
 Documentation/devicetree/bindings/mmc/renesas,sdhi.yaml | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/devicetree/bindings/mmc/renesas,sdhi.yaml b/Documentation/devicetree/bindings/mmc/renesas,sdhi.yaml
index c754ea71f51f..64fac0d11329 100644
--- a/Documentation/devicetree/bindings/mmc/renesas,sdhi.yaml
+++ b/Documentation/devicetree/bindings/mmc/renesas,sdhi.yaml
@@ -106,6 +106,11 @@ properties:
   iommus:
     maxItems: 1
 
+  mux-states:
+    description:
+      mux controller node to route the SD/SDIO/eMMC signals from SoC to cards.
+    maxItems: 1
+
   power-domains:
     maxItems: 1
 
@@ -275,6 +280,7 @@ examples:
         max-frequency = <195000000>;
         power-domains = <&sysc R8A7790_PD_ALWAYS_ON>;
         resets = <&cpg 314>;
+        mux-states = <&mux 0>;
     };
 
     sdhi1: mmc@ee120000 {

-- 
2.43.0

[PATCH v7 7/7] mmc: host: renesas_sdhi_core: support selecting an optional mux

[Josua Mayer]

Some hardware designs route data or control signals through a mux to
support multiple devices on a single sdhi controller.

In particular SolidRun RZ/G2L/G2LC/V2L System on Module use a mux for
switching between soldered eMMC and an optional microSD on a carrier
board, e.g. for development or provisioning.

SD/SDIO/eMMC are not well suited for runtime switching between different
cards, however boot-time selection is possible and useful - in
particular considering dt overlays.

Add support for an optional SD/SDIO/eMMC mux defined in dt, and select
it during probe.

Similar functionality already exists in other places, e.g. i2c-omap.

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Josua Mayer <josua@solid-run.com>
---
 drivers/mmc/host/renesas_sdhi_core.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/mmc/host/renesas_sdhi_core.c b/drivers/mmc/host/renesas_sdhi_core.c
index 2a310a145785..f9ec78d699f4 100644
--- a/drivers/mmc/host/renesas_sdhi_core.c
+++ b/drivers/mmc/host/renesas_sdhi_core.c
@@ -26,6 +26,7 @@
 #include <linux/mmc/mmc.h>
 #include <linux/mmc/slot-gpio.h>
 #include <linux/module.h>
+#include <linux/mux/consumer.h>
 #include <linux/pinctrl/consumer.h>
 #include <linux/pinctrl/pinctrl-state.h>
 #include <linux/platform_data/tmio.h>
@@ -1062,6 +1063,7 @@ int renesas_sdhi_probe(struct platform_device *pdev,
 	struct regulator_dev *rdev;
 	struct renesas_sdhi_dma *dma_priv;
 	struct device *dev = &pdev->dev;
+	struct mux_state *mux_state;
 	struct tmio_mmc_host *host;
 	struct renesas_sdhi *priv;
 	int num_irqs, irq, ret, i;
@@ -1116,6 +1118,10 @@ int renesas_sdhi_probe(struct platform_device *pdev,
 						"state_uhs");
 	}
 
+	mux_state = devm_mux_state_get_optional_selected(&pdev->dev, NULL);
+	if (IS_ERR(mux_state))
+		return PTR_ERR(mux_state);
+
 	host = tmio_mmc_host_alloc(pdev, mmc_data);
 	if (IS_ERR(host))
 		return PTR_ERR(host);

-- 
2.43.0

Re: [PATCH v7 2/7] mux: Add helper functions for getting optional and selected mux-state

[Ulf Hansson]

On Wed, 28 Jan 2026 at 15:46, Josua Mayer <josua@solid-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@solid-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?

> +               goto err_mux_state_get;
>         }
>
> -       *ptr = mstate;
> -       devres_add(dev, ptr);
> +       if (init) {
> +               ret = init(mstate);
> +               if (ret)
> +                       goto err_mux_state_init;
> +       }
> +
> +       devm_state->mstate = mstate;
> +       devm_state->exit = exit;
> +       devres_add(dev, devm_state);
>
>         return mstate;
> +
> +err_mux_state_init:
> +       mux_state_put(mstate);
> +err_mux_state_get:
> +       devres_free(devm_state);
> +       return ERR_PTR(ret);

If PTR_ERR_OR_ZERO is used above as I suggested, ret may be 0 here.

Then it is probably clearer to add a check if (!ret) and return NULL
explicitly for that case, I think.

[...]

Kind regards
Uffe

Re: [PATCH v7 2/7] mux: Add helper functions for getting optional and selected mux-state

[Geert Uytterhoeven]

On Thu, 29 Jan 2026 at 17:06, Ulf Hansson <ulf.hansson@linaro.org> wrote:
> On Wed, 28 Jan 2026 at 15:46, Josua Mayer <josua@solid-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@solid-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@linux-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

Re: [PATCH v7 0/7] mmc: host: renesas_sdhi_core: support configuring an optional sdio mux

[Ulf Hansson]

On Wed, 28 Jan 2026 at 15:46, Josua Mayer <josua@solid-run.com> wrote:
>
> Some Renesas SoC based boards mux SD and eMMC on a single sdio
> controller, exposing user control by dip switch and software control by
> gpio.
>
> Purpose is to simplify development and provisioning by selecting boot
> media at power-on, and again before starting linux.
>
> Add binding and driver support for linking a (gpio) mux to renesas sdio
> controller.
>
> Introduce generic helper functions for getting managed and selected
> mux-state objects, and switch i2c-omap and phy-can-transceiver drivers.
>
> Signed-off-by: Josua Mayer <josua@solid-run.com>

This series needs to go together in some way. If you like, I can
funnel it via my mmc tree, unless someone (Wolfram for the i2c part?)
has objections to this of course.

Kind regards
Uffe

> ---
> Changes in v7:
> - picked up reviewed-tags
> - fix Kconfig change to add the missing prompt for CONFIG_MULTIPLEXER,
>   and enable it by default when COMPILE_TEST is set.
>   (Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>)
> - fix another kernel build robot warning: undocumented C struct member
> - Link to v6: https://lore.kernel.org/r/20260121-rz-sdio-mux-v6-0-38aa39527928@solid-run.com
>
> Changes in v6:
> - replaced /* with /** for devm_mux_state_state function description.
> - collected review tags.
> - fixed checkpatch warnings (space-before-tab, void-return).
>   (Reported-by: Geert Uytterhoeven)
> - fixed use-after-free in mux core mux_get function.
>   (Reported-by: Geert Uytterhoeven)
> - fix mux helper error path uninitialised return code variable.
>   (Reported-by: kernel test robot <lkp@intel.com>)
> - Link to v5: https://lore.kernel.org/r/20260118-rz-sdio-mux-v5-0-3c37e8872683@solid-run.com
>
> Changes in v5:
> - implemented automatic mux deselect for devm_*_selected.
>   (Reported-by: Wolfram Sang <wsa+renesas@sang-engineering.com>)
> - because of semantic changes I dropped reviewed and acks from omap-i2c
>   patch (Andreas Kemnade / Wolfram Sang).
> - fix invalid return value in void function for mux helper stubs
>   (Reported-by: kernel test robot <lkp@intel.com>)
> - Link to v4: https://lore.kernel.org/r/20251229-rz-sdio-mux-v4-0-a023e55758fe@solid-run.com
>
> Changes in v4:
> - added MULTIPLEXER Kconfig help text.
> - removed "select MULTIPLEXER" from renesas sdhi Kconfig, as it is
>   not required for all devices using this driver.
> - added stubs for all symbols exported by mux core.
>   (Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>)
> - refactored mux core logic to silence ENOENT errors only on optional
>   code paths, keeping error printing unchanged otherwise.
>   (Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>)
> - picked up various reviewed- and acked-by tags
> - Link to v3: https://lore.kernel.org/r/20251210-rz-sdio-mux-v3-0-ca628db56d60@solid-run.com
>
> Changes in v3:
> - updated omap-i2c and phy-can-transceiver to use new helpers.
> - created generic helper functions for getting managed optional mux-state.
>   (Reported-by: Rob Herring <robh@kernel.org>)
> - picked up binding ack by Rob Herring.
> - replaced use of "SDIO" with "SD/SDIO/eMMC" in binding document and
>   commit descriptions.
>   (Reported-by: Ulf Hansson <ulf.hansson@linaro.org>)
> - Link to v2: https://lore.kernel.org/r/20251201-rz-sdio-mux-v2-0-bcb581b88dd7@solid-run.com
>
> Changes in v2:
> - dropped mux-controller node from dt binding example
>   (Reported-by: Conor Dooley <conor@kernel.org>
>    Reported-by: Krzysztof Kozlowski <krzk@kernel.org>)
> - Link to v1: https://lore.kernel.org/r/20251128-rz-sdio-mux-v1-0-1ede318d160f@solid-run.com
>
> ---
> Josua Mayer (7):
>       phy: can-transceiver: rename temporary helper function to avoid conflict
>       mux: Add helper functions for getting optional and selected mux-state
>       mux: add help text for MULTIPLEXER config option
>       phy: can-transceiver: drop temporary helper getting optional mux-state
>       i2c: omap: switch to new generic helper for getting selected mux-state
>       dt-bindings: mmc: renesas,sdhi: Add mux-states property
>       mmc: host: renesas_sdhi_core: support selecting an optional mux
>
>  .../devicetree/bindings/mmc/renesas,sdhi.yaml      |   6 +
>  drivers/i2c/busses/i2c-omap.c                      |  24 +--
>  drivers/mmc/host/renesas_sdhi_core.c               |   6 +
>  drivers/mux/Kconfig                                |   8 +-
>  drivers/mux/core.c                                 | 178 +++++++++++++++++----
>  drivers/phy/phy-can-transceiver.c                  |  10 --
>  include/linux/mux/consumer.h                       | 108 ++++++++++++-
>  7 files changed, 277 insertions(+), 63 deletions(-)
> ---
> base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8
> change-id: 20251128-rz-sdio-mux-acc5137f1618
>
> Best regards,
> --
> Josua Mayer <josua@solid-run.com>
>
>

Re: [PATCH v7 0/7] mmc: host: renesas_sdhi_core: support configuring an optional sdio mux

[Wolfram Sang]

On Thu, Jan 29, 2026 at 05:15:06PM +0100, Ulf Hansson wrote:
> On Wed, 28 Jan 2026 at 15:46, Josua Mayer <josua@solid-run.com> wrote:
> >
> > Some Renesas SoC based boards mux SD and eMMC on a single sdio
> > controller, exposing user control by dip switch and software control by
> > gpio.
> >
> > Purpose is to simplify development and provisioning by selecting boot
> > media at power-on, and again before starting linux.
> >
> > Add binding and driver support for linking a (gpio) mux to renesas sdio
> > controller.
> >
> > Introduce generic helper functions for getting managed and selected
> > mux-state objects, and switch i2c-omap and phy-can-transceiver drivers.
> >
> > Signed-off-by: Josua Mayer <josua@solid-run.com>
> 
> This series needs to go together in some way. If you like, I can
> funnel it via my mmc tree, unless someone (Wolfram for the i2c part?)
> has objections to this of course.

No objections, I even acked the I2C patch in a previous series. Since
the series changed because of some of my suggestions, I want to have
another look at it. But yes, your tree sounds very reasonable.

Re: [PATCH v7 2/7] mux: Add helper functions for getting optional and selected mux-state

[Ulf Hansson]

On Thu, 29 Jan 2026 at 18:46, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>
> On Thu, 29 Jan 2026 at 17:06, Ulf Hansson <ulf.hansson@linaro.org> wrote:
> > On Wed, 28 Jan 2026 at 15:46, Josua Mayer <josua@solid-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@solid-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

By looking at the code in mux_state_get() and mux_get() that $subject
patch changes, it intends to add a "bool optional" as in-parameter. If
it's set, it looks like the intent is to allow returning NULL, which
makes sense to me.

Anyway, there seems to be some additional smatch warnings to fix
before this is ready to go.

[...]

Kind regards
Uffe

Re: [PATCH v7 2/7] mux: Add helper functions for getting optional and selected mux-state

[Josua Mayer]

On 30/01/2026 12:28, Ulf Hansson wrote:
> On Thu, 29 Jan 2026 at 18:46, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>> On Thu, 29 Jan 2026 at 17:06, Ulf Hansson <ulf.hansson@linaro.org> wrote:
>>> On Wed, 28 Jan 2026 at 15:46, Josua Mayer <josua@solid-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@solid-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
> By looking at the code in mux_state_get() and mux_get() that $subject
> patch changes, it intends to add a "bool optional" as in-parameter. If
> it's set, it looks like the intent is to allow returning NULL, which
> makes sense to me.
The intent behind "optional" parameter was to conditionally
silence certain error paths that would eventually lead to
at least the exported devm_* functions to return NULL.

I'll review my logic ...

>
> Anyway, there seems to be some additional smatch warnings to fix
> before this is ready to go.
>
> [...]
>
> Kind regards
> Uffe
>

Re: [PATCH v7 2/7] mux: Add helper functions for getting optional and selected mux-state

[Josua Mayer]

On 29/01/2026 18:13, Geert Uytterhoeven wrote:
> On Thu, 29 Jan 2026 at 17:06, Ulf Hansson <ulf.hansson@linaro.org> wrote:
>> On Wed, 28 Jan 2026 at 15:46, Josua Mayer <josua@solid-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@solid-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

mux_state_get after my modifications does return NULL:

     if (mux_name) {
         ...
         if (index < 0 && optional) {
             return NULL;
         ...
     }
...
     if (ret) {
         if (optional && ret == -ENOENT)
             return NULL;
...

>
>>> +               goto err_mux_state_get;
>>>          }
> Gr{oetje,eeting}s,
>
>                          Geert
>

Re: [PATCH v7 2/7] mux: Add helper functions for getting optional and selected mux-state

[Dan Carpenter]

Sorry about that, I just looked at the implementation in linux-next and
didn't read the code from the patch too closely.

On Wed, Jan 28, 2026 at 04:46:10PM +0200, Josua Mayer wrote:
> +/**
> + * 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.

I wish the documentation for these "optional" said it could return NULL.

> + */
> +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);
> +

regards,
dan carpenter

Re: [PATCH v7 2/7] mux: Add helper functions for getting optional and selected mux-state

[Josua Mayer]

On 03/02/2026 17:05, Dan Carpenter wrote:
> Sorry about that, I just looked at the implementation in linux-next and
> didn't read the code from the patch too closely.
:)
>
> On Wed, Jan 28, 2026 at 04:46:10PM +0200, Josua Mayer wrote:
>> +/**
>> + * 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.
> I wish the documentation for these "optional" said it could return NULL.
Same. I fixed that for v8 on most functions, but missed one .... .
>
>> + */
>> +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);
>> +