[PATCH v12 2/7] i2c: mux: add idle_state property to i2c_mux_core

[Marcus Folkesson]

Muxes treat their channels differently when idle.
Let the mux core have this information to make it available for
internal use.

Possible idle states are:
 - I2C_MUX_IDLE_AS_IS: Leave channels as is when idle
 - I2C_MUX_IDLE_DISCONNECT: Disconnect channel (set HiZ when idle)
 - I2C_MUX_IDLE_UNKNOWN: Unknown idle state
 - <n>: Enable channel n (starting from 0) when idle"

Default value is set to I2C_MUX_IDLE_UNKNOWN.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxx>
Signed-off-by: Marcus Folkesson <marcus.folkesson@xxxxxxxxx>
---
 drivers/i2c/i2c-mux.c   |  1 +
 include/linux/i2c-mux.h | 30 ++++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
index 681a201c239b..b126ce7338c2 100644
--- a/drivers/i2c/i2c-mux.c
+++ b/drivers/i2c/i2c-mux.c
@@ -247,6 +247,7 @@ struct i2c_mux_core *i2c_mux_alloc(struct i2c_adapter *parent,
 	muxc->select = select;
 	muxc->deselect = deselect;
 	muxc->max_adapters = max_adapters;
+	muxc->idle_state = I2C_MUX_IDLE_UNKNOWN;
 
 	return muxc;
 }
diff --git a/include/linux/i2c-mux.h b/include/linux/i2c-mux.h
index 1784ac7afb11..a348f81e7a90 100644
--- a/include/linux/i2c-mux.h
+++ b/include/linux/i2c-mux.h
@@ -15,6 +15,10 @@
 
 #include <linux/bitops.h>
 
+#define I2C_MUX_IDLE_AS_IS      (-1)
+#define I2C_MUX_IDLE_DISCONNECT (-2)
+#define I2C_MUX_IDLE_UNKNOWN	(-3)
+
 struct i2c_mux_core {
 	struct i2c_adapter *parent;
 	struct device *dev;
@@ -22,6 +26,18 @@ struct i2c_mux_core {
 	unsigned int arbitrator:1;
 	unsigned int gate:1;
 
+	/*
+	 * The mux state used by the driver when idle.
+	 * Possible idle states are:
+	 *  - I2C_MUX_IDLE_AS_IS: Leave channels as is when idle
+	 *  - I2C_MUX_IDLE_DISCONNECT: Disconnect channel (set HiZ when idle)
+	 *  - I2C_MUX_IDLE_UNKNOWN: Unknown idle state
+	 *  - <n>: Enable channel n (starting from 0) when idle"
+	 *
+	 * Default value is set to I2C_MUX_IDLE_UNKNOWN.
+	 */
+	int idle_state;
+
 	void *priv;
 
 	int (*select)(struct i2c_mux_core *, u32 chan_id);
@@ -38,6 +54,20 @@ struct i2c_mux_core *i2c_mux_alloc(struct i2c_adapter *parent,
 				   int (*select)(struct i2c_mux_core *, u32),
 				   int (*deselect)(struct i2c_mux_core *, u32));
 
+/*
+ * Mux drivers may only change idle_state, and may only do so
+ * between allocation and registration of the mux controller.
+ */
+static inline void i2c_mux_set_idle_state(struct i2c_mux_core *muxc, int state)
+{
+	muxc->idle_state = state;
+}
+
+static inline int i2c_mux_idle_state(struct i2c_mux_core *muxc)
+{
+	return muxc->idle_state;
+}
+
 /* flags for i2c_mux_alloc */
 #define I2C_MUX_LOCKED     BIT(0)
 #define I2C_MUX_ARBITRATOR BIT(1)

-- 
2.54.0