Allow the mux (if it's an I2C device) to have the same address as a child
device. This is useful when the mux can only use an I2C address that is
used by a child device because no other addresses are free to use.
eg. the mux can only use address 0x18 which is used by amc6821 connected
to the mux.
Signed-off-by: Farouk Bouabid <[email protected]>
---
drivers/i2c/i2c-core-base.c | 6 +++++-
drivers/i2c/i2c-mux.c | 48 ++++++++++++++++++++++++++++++++++++++++++++-
include/linux/i2c-mux.h | 1 +
include/linux/i2c.h | 7 +++++++
4 files changed, 60 insertions(+), 2 deletions(-)
diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index ff5c486a1dbb..ce2425b0486d 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -821,9 +821,13 @@ static int i2c_check_mux_children(struct device *dev, void *addrp)
static int i2c_check_addr_busy(struct i2c_adapter *adapter, int addr)
{
struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);
+ bool skip_check = false;
int result = 0;
- if (parent)
+ if (adapter->quirks && adapter->quirks->flags & I2C_AQ_SKIP_ADDR_CHECK)
+ skip_check = adapter->quirks->skip_addr_in_parent == addr;
+
+ if (parent && !skip_check)
result = i2c_check_mux_parents(parent, addr);
if (!result)
diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
index 57ff09f18c37..644509bc3496 100644
--- a/drivers/i2c/i2c-mux.c
+++ b/drivers/i2c/i2c-mux.c
@@ -334,7 +334,53 @@ int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
priv->adap.dev.parent = &parent->dev;
priv->adap.retries = parent->retries;
priv->adap.timeout = parent->timeout;
- priv->adap.quirks = parent->quirks;
+
+ struct i2c_adapter_quirks *quirks;
+ /*
+ * When creating the adapter, the node devices are checked for I2C address
+ * match with other devices on the parent adapter, among which is the mux itself.
+ * If a match is found the node device is not probed successfully.
+ * Allow the mux to have the same address as a child device by skipping this check.
+ */
+ if (muxc->share_addr_with_children) {
+ struct i2c_client *client = to_i2c_client(muxc->dev);
+
+ if (muxc->dev->type != &i2c_client_type)
+ dev_warn_once(muxc->dev, "Mux is not an I2C device\n");
+
+ quirks = devm_kzalloc(muxc->dev, sizeof(*quirks), GFP_KERNEL);
+ if (!quirks)
+ return -ENOMEM;
+
+ if (parent->quirks)
+ memcpy(quirks, parent->quirks, sizeof(*quirks));
+
+ quirks->flags |= I2C_AQ_SKIP_ADDR_CHECK;
+ quirks->skip_addr_in_parent = client->addr;
+ priv->adap.quirks = quirks;
+
+ } else if (parent->quirks &&
+ parent->quirks->flags & I2C_AQ_SKIP_ADDR_CHECK) {
+ /*
+ * Another I2C mux device can be a child of the Mule I2C mux.
+ * The former could probably not allow address conflict between
+ * its address and its own children addresses.
+ *
+ * For this purpose, do not propagate this flag unless
+ * share_addr_with_children is set.
+ */
+ quirks = devm_kzalloc(muxc->dev, sizeof(*quirks), GFP_KERNEL);
+ if (!quirks)
+ return -ENOMEM;
+
+ memcpy(quirks, parent->quirks, sizeof(*quirks));
+ quirks->flags &= ~I2C_AQ_SKIP_ADDR_CHECK;
+ priv->adap.quirks = quirks;
+
+ } else {
+ priv->adap.quirks = parent->quirks;
+ }
+
if (muxc->mux_locked)
priv->adap.lock_ops = &i2c_mux_lock_ops;
else
diff --git a/include/linux/i2c-mux.h b/include/linux/i2c-mux.h
index 98ef73b7c8fd..17ac68bf1703 100644
--- a/include/linux/i2c-mux.h
+++ b/include/linux/i2c-mux.h
@@ -21,6 +21,7 @@ struct i2c_mux_core {
unsigned int mux_locked:1;
unsigned int arbitrator:1;
unsigned int gate:1;
+ unsigned int share_addr_with_children:1;
void *priv;
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 5e6cd43a6dbd..c3acbaaadae9 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -670,6 +670,7 @@ int i2c_generic_scl_recovery(struct i2c_adapter *adap);
* @max_read_len: maximum length of a read message
* @max_comb_1st_msg_len: maximum length of the first msg in a combined message
* @max_comb_2nd_msg_len: maximum length of the second msg in a combined message
+ * @skip_addr_in_parent: No conflict check on parent adapter for a given address
*
* Note about combined messages: Some I2C controllers can only send one message
* per transfer, plus something called combined message or write-then-read.
@@ -690,6 +691,7 @@ struct i2c_adapter_quirks {
u16 max_read_len;
u16 max_comb_1st_msg_len;
u16 max_comb_2nd_msg_len;
+ unsigned short skip_addr_in_parent;
};
/* enforce max_num_msgs = 2 and use max_comb_*_len for length checks */
@@ -711,6 +713,11 @@ struct i2c_adapter_quirks {
#define I2C_AQ_NO_ZERO_LEN (I2C_AQ_NO_ZERO_LEN_READ | I2C_AQ_NO_ZERO_LEN_WRITE)
/* adapter cannot do repeated START */
#define I2C_AQ_NO_REP_START BIT(7)
+/**
+ * do not check for conflict on a given address
+ * used accordingly with "struct i2c_adapter_quirks.skip_addr_in_parent"
+ */
+#define I2C_AQ_SKIP_ADDR_CHECK BIT(8)
/*
* i2c_adapter is the structure used to identify a physical i2c bus along
--
2.34.1
Le 11/06/2024 à 13:43, Farouk Bouabid a écrit :
> Allow the mux (if it's an I2C device) to have the same address as a child
> device. This is useful when the mux can only use an I2C address that is
> used by a child device because no other addresses are free to use.
> eg. the mux can only use address 0x18 which is used by amc6821 connected
> to the mux.
>
> Signed-off-by: Farouk Bouabid <[email protected]>
> ---
Hi,
2 nitpicks below.
> --- a/drivers/i2c/i2c-mux.c
> +++ b/drivers/i2c/i2c-mux.c
> @@ -334,7 +334,53 @@ int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
> priv->adap.dev.parent = &parent->dev;
> priv->adap.retries = parent->retries;
> priv->adap.timeout = parent->timeout;
> - priv->adap.quirks = parent->quirks;
> +
> + struct i2c_adapter_quirks *quirks;
Should this be at the beginning of the function?
> + /*
> + * When creating the adapter, the node devices are checked for I2C address
> + * match with other devices on the parent adapter, among which is the mux itself.
> + * If a match is found the node device is not probed successfully.
> + * Allow the mux to have the same address as a child device by skipping this check.
> + */
> + if (muxc->share_addr_with_children) {
> + struct i2c_client *client = to_i2c_client(muxc->dev);
> +
> + if (muxc->dev->type != &i2c_client_type)
> + dev_warn_once(muxc->dev, "Mux is not an I2C device\n");
> +
> + quirks = devm_kzalloc(muxc->dev, sizeof(*quirks), GFP_KERNEL);
> + if (!quirks)
> + return -ENOMEM;
> +
> + if (parent->quirks)
> + memcpy(quirks, parent->quirks, sizeof(*quirks));
> +
> + quirks->flags |= I2C_AQ_SKIP_ADDR_CHECK;
> + quirks->skip_addr_in_parent = client->addr;
> + priv->adap.quirks = quirks;
> +
> + } else if (parent->quirks &&
> + parent->quirks->flags & I2C_AQ_SKIP_ADDR_CHECK) {
> + /*
> + * Another I2C mux device can be a child of the Mule I2C mux.
> + * The former could probably not allow address conflict between
> + * its address and its own children addresses.
> + *
> + * For this purpose, do not propagate this flag unless
> + * share_addr_with_children is set.
> + */
> + quirks = devm_kzalloc(muxc->dev, sizeof(*quirks), GFP_KERNEL);
devm_kmemdup()? (not sure it is a win)
> + if (!quirks)
> + return -ENOMEM;
> +
> + memcpy(quirks, parent->quirks, sizeof(*quirks));
> + quirks->flags &= ~I2C_AQ_SKIP_ADDR_CHECK;
> + priv->adap.quirks = quirks;
> +
> + } else {
> + priv->adap.quirks = parent->quirks;
> + }
> +
> if (muxc->mux_locked)
> priv->adap.lock_ops = &i2c_mux_lock_ops;
> else
...
CJ