[PATCH v3 2/6] mux: Add helper functions for getting optional and selected mux-state

Josua Mayer
2025-12-10T17:39:25Z

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:

- devm_mux_state_get_optional:
Get a mux-state if specified in dt, return NULL 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 return -ENOENT in case dt
did not specify a mux-state or -control matching given name (if valid).
This matches of_parse_phandle_with_args semantics which also returns
-ENOENT if the property does nto exists, or its value is zero.

The new helper functions check for ENOENT to return NULL for optional
muxes.

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. This is removed as the returned error code (-ENOENT) is clear.

The second error message is based on of_parse_phandle_with_args return
value. In case mux description is missing from DT, it returns -ENOENT.
Print error message only for other error codes.

This ensures that the new helper functions will not confuse the user
either.

Signed-off-by: Josua Mayer <josua@solid-run.com>
---
drivers/mux/core.c | 67 +++++++++++++++++++++++++++++++++++++++-----
include/linux/mux/consumer.h | 4 +++
2 files changed, 64 insertions(+), 7 deletions(-)

diff --git a/drivers/mux/core.c b/drivers/mux/core.c
index a3840fe0995fe..130ca47a8be37 100644
--- a/drivers/mux/core.c
+++ b/drivers/mux/core.c
@@ -542,11 +542,8 @@ 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) {
- dev_err(dev, "mux controller '%s' not found\n",
- mux_name);
- return ERR_PTR(index);
- }
+ if (index < 0)
+ return ERR_PTR(-ENOENT);
}

if (state)
@@ -558,8 +555,10 @@ static struct mux_control *mux_get(struct device *dev, const char *mux_name,
"mux-controls", "#mux-control-cells",
index, &args);
if (ret) {
- dev_err(dev, "%pOF: failed to get mux-%s %s(%i)\n",
- np, state ? "state" : "control", mux_name ?: "", index);
+ if (ret != -ENOENT)
+ dev_err(dev, "%pOF: failed to get mux-%s %s(%i)\n",
+ np, state ? "state" : "control",
+ mux_name ?: "", index);
return ERR_PTR(ret);
}

@@ -745,6 +744,60 @@ struct mux_state *devm_mux_state_get(struct device *dev,
}
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.
+ */
+struct mux_state *devm_mux_state_get_optional(struct device *dev,
+ const char *mux_name)
+{
+ struct mux_state *mux_state = devm_mux_state_get(dev, mux_name);
+
+ if (IS_ERR(mux_state) && PTR_ERR(mux_state) == -ENOENT)
+ return NULL;
+
+ return mux_state;
+}
+EXPORT_SYMBOL_GPL(devm_mux_state_get_optional);
+
+/**
+ * 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.
+ */
+struct mux_state *devm_mux_state_get_optional_selected(struct device *dev,
+ const char *mux_name)
+{
+ struct mux_state *mux_state;
+ int ret;
+
+ mux_state = devm_mux_state_get_optional(dev, mux_name);
+ if (IS_ERR_OR_NULL(mux_state))
+ return mux_state;
+
+ ret = mux_state_select(mux_state);
+ if (ret) {
+ if (ret != -EPROBE_DEFER)
+ dev_err(dev, "failed to select mux-state %s: %d\n",
+ mux_name ?: "", ret);
+
+ mux_state_put(mux_state);
+ return ERR_PTR(ret);
+ }
+
+ return mux_state;
+}
+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 2e25c838f8312..a5da2e33a45c0 100644
--- a/include/linux/mux/consumer.h
+++ b/include/linux/mux/consumer.h
@@ -60,5 +60,9 @@ 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_optional_selected(struct device *dev,
+ const char *mux_name);

#endif /* _LINUX_MUX_CONSUMER_H */

--
2.51.0