[PATCH v6 4/9] i2c: use client addresses directly in ATR interface

Romain Gantois
2025-01-15T09:26:09Z

The I2C Address Translator (ATR) module defines mappings from i2c_client
structs to aliases. However, only the physical address of each i2c_client
struct is actually relevant to the workings of the ATR module. Moreover,
some drivers require address translation functionality but do not allocate
i2c_client structs, accessing the adapter directly instead. The SFP
subsystem is an example of this.

Replace the "i2c_client" field of the i2c_atr_alias_pair struct with a u16
"addr" field. Rewrite helper functions and callbacks as needed.

Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Romain Gantois <romain.gantois@bootlin.com>
---
drivers/i2c/i2c-atr.c | 52 ++++++++++++++++---------------------------
drivers/media/i2c/ds90ub960.c | 24 ++++++++++----------
include/linux/i2c-atr.h | 20 ++++++++---------
3 files changed, 41 insertions(+), 55 deletions(-)

diff --git a/drivers/i2c/i2c-atr.c b/drivers/i2c/i2c-atr.c
index f21475ae592183a45b5e46a20e7a0699fb88132c..f04bd4f9e3143837c035cd08d23d5dfc37f151cb 100644
--- a/drivers/i2c/i2c-atr.c
+++ b/drivers/i2c/i2c-atr.c
@@ -21,16 +21,16 @@
#define ATR_MAX_SYMLINK_LEN 11 /* Longest name is 10 chars: "channel-99" */

/**
- * struct i2c_atr_alias_pair - Holds the alias assigned to a client.
+ * struct i2c_atr_alias_pair - Holds the alias assigned to a client address.
* @node: List node
- * @client: Pointer to the client on the child bus
+ * @addr: Address of the client on the child bus.
* @alias: I2C alias address assigned by the driver.
* This is the address that will be used to issue I2C transactions
* on the parent (physical) bus.
*/
struct i2c_atr_alias_pair {
struct list_head node;
- const struct i2c_client *client;
+ u16 addr;
u16 alias;
};

@@ -97,27 +97,13 @@ struct i2c_atr {
struct i2c_adapter *adapter[] __counted_by(max_adapters);
};

-static struct i2c_atr_alias_pair *
-i2c_atr_find_mapping_by_client(const struct list_head *list,
- const struct i2c_client *client)
-{
- struct i2c_atr_alias_pair *c2a;
-
- list_for_each_entry(c2a, list, node) {
- if (c2a->client == client)
- return c2a;
- }
-
- return NULL;
-}
-
static struct i2c_atr_alias_pair *
i2c_atr_find_mapping_by_addr(const struct list_head *list, u16 phys_addr)
{
struct i2c_atr_alias_pair *c2a;

list_for_each_entry(c2a, list, node) {
- if (c2a->client->addr == phys_addr)
+ if (c2a->addr == phys_addr)
return c2a;
}

@@ -313,8 +299,8 @@ static void i2c_atr_release_alias(struct i2c_atr *atr, u16 alias)
dev_warn(atr->dev, "Unable to find mapped alias\n");
}

-static int i2c_atr_attach_client(struct i2c_adapter *adapter,
- const struct i2c_client *client)
+static int i2c_atr_attach_addr(struct i2c_adapter *adapter,
+ u16 addr)
{
struct i2c_atr_chan *chan = adapter->algo_data;
struct i2c_atr *atr = chan->atr;
@@ -334,14 +320,14 @@ static int i2c_atr_attach_client(struct i2c_adapter *adapter,
goto err_release_alias;
}

- ret = atr->ops->attach_client(atr, chan->chan_id, client, alias);
+ ret = atr->ops->attach_addr(atr, chan->chan_id, addr, alias);
if (ret)
goto err_free;

- dev_dbg(atr->dev, "chan%u: client 0x%02x mapped at alias 0x%02x (%s)\n",
- chan->chan_id, client->addr, alias, client->name);
+ dev_dbg(atr->dev, "chan%u: using alias 0x%02x for addr 0x%02x\n",
+ chan->chan_id, alias, addr);

- c2a->client = client;
+ c2a->addr = addr;
c2a->alias = alias;
list_add(&c2a->node, &chan->alias_list);

@@ -355,16 +341,16 @@ static int i2c_atr_attach_client(struct i2c_adapter *adapter,
return ret;
}

-static void i2c_atr_detach_client(struct i2c_adapter *adapter,
- const struct i2c_client *client)
+static void i2c_atr_detach_addr(struct i2c_adapter *adapter,
+ u16 addr)
{
struct i2c_atr_chan *chan = adapter->algo_data;
struct i2c_atr *atr = chan->atr;
struct i2c_atr_alias_pair *c2a;

- atr->ops->detach_client(atr, chan->chan_id, client);
+ atr->ops->detach_addr(atr, chan->chan_id, addr);

- c2a = i2c_atr_find_mapping_by_client(&chan->alias_list, client);
+ c2a = i2c_atr_find_mapping_by_addr(&chan->alias_list, addr);
if (!c2a) {
/* This should never happen */
dev_warn(atr->dev, "Unable to find address mapping\n");
@@ -374,8 +360,8 @@ static void i2c_atr_detach_client(struct i2c_adapter *adapter,
i2c_atr_release_alias(atr, c2a->alias);

dev_dbg(atr->dev,
- "chan%u: client 0x%02x unmapped from alias 0x%02x (%s)\n",
- chan->chan_id, client->addr, c2a->alias, client->name);
+ "chan%u: detached alias 0x%02x from addr 0x%02x\n",
+ chan->chan_id, c2a->alias, addr);

list_del(&c2a->node);
kfree(c2a);
@@ -405,7 +391,7 @@ static int i2c_atr_bus_notifier_call(struct notifier_block *nb,

switch (event) {
case BUS_NOTIFY_ADD_DEVICE:
- ret = i2c_atr_attach_client(client->adapter, client);
+ ret = i2c_atr_attach_addr(client->adapter, client->addr);
if (ret)
dev_err(atr->dev,
"Failed to attach remote client '%s': %d\n",
@@ -413,7 +399,7 @@ static int i2c_atr_bus_notifier_call(struct notifier_block *nb,
break;

case BUS_NOTIFY_DEL_DEVICE:
- i2c_atr_detach_client(client->adapter, client);
+ i2c_atr_detach_addr(client->adapter, client->addr);
break;

default:
@@ -506,7 +492,7 @@ struct i2c_atr *i2c_atr_new(struct i2c_adapter *parent, struct device *dev,
if (max_adapters > ATR_MAX_ADAPTERS)
return ERR_PTR(-EINVAL);

- if (!ops || !ops->attach_client || !ops->detach_client)
+ if (!ops || !ops->attach_addr || !ops->detach_addr)
return ERR_PTR(-EINVAL);

atr = kzalloc(struct_size(atr, adapter, max_adapters), GFP_KERNEL);
diff --git a/drivers/media/i2c/ds90ub960.c b/drivers/media/i2c/ds90ub960.c
index 0c83c07c287c5eb168ec5d761f3d803c96d1e649..92bdd9f44c4d138903cf4ef45bed1c20687589ad 100644
--- a/drivers/media/i2c/ds90ub960.c
+++ b/drivers/media/i2c/ds90ub960.c
@@ -1026,8 +1026,8 @@ static int ub960_ind_update_bits(struct ub960_data *priv, u8 block, u8 reg,
* I2C-ATR (address translator)
*/

-static int ub960_atr_attach_client(struct i2c_atr *atr, u32 chan_id,
- const struct i2c_client *client, u16 alias)
+static int ub960_atr_attach_addr(struct i2c_atr *atr, u32 chan_id,
+ u16 addr, u16 alias)
{
struct ub960_data *priv = i2c_atr_get_driver_data(atr);
struct ub960_rxport *rxport = priv->rxports[chan_id];
@@ -1046,21 +1046,21 @@ static int ub960_atr_attach_client(struct i2c_atr *atr, u32 chan_id,
return -EADDRNOTAVAIL;
}

- rxport->aliased_addrs[reg_idx] = client->addr;
+ rxport->aliased_addrs[reg_idx] = addr;

ub960_rxport_write(priv, chan_id, UB960_RR_SLAVE_ID(reg_idx),
- client->addr << 1);
+ addr << 1);
ub960_rxport_write(priv, chan_id, UB960_RR_SLAVE_ALIAS(reg_idx),
alias << 1);

dev_dbg(dev, "rx%u: client 0x%02x assigned alias 0x%02x at slot %u\n",
- rxport->nport, client->addr, alias, reg_idx);
+ rxport->nport, addr, alias, reg_idx);

return 0;
}

-static void ub960_atr_detach_client(struct i2c_atr *atr, u32 chan_id,
- const struct i2c_client *client)
+static void ub960_atr_detach_addr(struct i2c_atr *atr, u32 chan_id,
+ u16 addr)
{
struct ub960_data *priv = i2c_atr_get_driver_data(atr);
struct ub960_rxport *rxport = priv->rxports[chan_id];
@@ -1070,13 +1070,13 @@ static void ub960_atr_detach_client(struct i2c_atr *atr, u32 chan_id,
guard(mutex)(&rxport->aliased_addrs_lock);

for (reg_idx = 0; reg_idx < ARRAY_SIZE(rxport->aliased_addrs); reg_idx++) {
- if (rxport->aliased_addrs[reg_idx] == client->addr)
+ if (rxport->aliased_addrs[reg_idx] == addr)
break;
}

if (reg_idx == ARRAY_SIZE(rxport->aliased_addrs)) {
dev_err(dev, "rx%u: client 0x%02x is not mapped!\n",
- rxport->nport, client->addr);
+ rxport->nport, addr);
return;
}

@@ -1085,12 +1085,12 @@ static void ub960_atr_detach_client(struct i2c_atr *atr, u32 chan_id,
ub960_rxport_write(priv, chan_id, UB960_RR_SLAVE_ALIAS(reg_idx), 0);

dev_dbg(dev, "rx%u: client 0x%02x released at slot %u\n", rxport->nport,
- client->addr, reg_idx);
+ addr, reg_idx);
}

static const struct i2c_atr_ops ub960_atr_ops = {
- .attach_client = ub960_atr_attach_client,
- .detach_client = ub960_atr_detach_client,
+ .attach_addr = ub960_atr_attach_addr,
+ .detach_addr = ub960_atr_detach_addr,
};

static int ub960_init_atr(struct ub960_data *priv)
diff --git a/include/linux/i2c-atr.h b/include/linux/i2c-atr.h
index 4d5da161c22516b3294e73702ace7a4546cdd588..14c1f9175c0db6a8a9c6ef5d771ae68361132a76 100644
--- a/include/linux/i2c-atr.h
+++ b/include/linux/i2c-atr.h
@@ -20,20 +20,20 @@ struct i2c_atr;

/**
* struct i2c_atr_ops - Callbacks from ATR to the device driver.
- * @attach_client: Notify the driver of a new device connected on a child
- * bus, with the alias assigned to it. The driver must
- * configure the hardware to use the alias.
- * @detach_client: Notify the driver of a device getting disconnected. The
- * driver must configure the hardware to stop using the
- * alias.
+ * @attach_addr: Notify the driver of a new device connected on a child
+ * bus, with the alias assigned to it. The driver must
+ * configure the hardware to use the alias.
+ * @detach_addr: Notify the driver of a device getting disconnected. The
+ * driver must configure the hardware to stop using the
+ * alias.
*
* All these functions return 0 on success, a negative error code otherwise.
*/
struct i2c_atr_ops {
- int (*attach_client)(struct i2c_atr *atr, u32 chan_id,
- const struct i2c_client *client, u16 alias);
- void (*detach_client)(struct i2c_atr *atr, u32 chan_id,
- const struct i2c_client *client);
+ int (*attach_addr)(struct i2c_atr *atr, u32 chan_id,
+ u16 addr, u16 alias);
+ void (*detach_addr)(struct i2c_atr *atr, u32 chan_id,
+ u16 addr);
};

/**

--
2.47.1