[PATCH v4 3/9] media: i2c: ds90ub960: Protect alias_use_mask with a mutex

Romain Gantois
2024-12-30T13:22:27Z

The aliased_addrs list represents the occupation of an RX port's hardware
alias table. This list and the underlying hardware table are only accessed
in the attach/detach_client() callbacks.

These functions are only called from a bus notifier handler in i2c-atr.c,
which is always called with the notifier chain's semaphore held. This
indirectly prevents concurrent access to the aliased_addrs list.
However, more explicit and direct locking is preferable. Moreover, with the
introduction of dynamic address translation in a future patch, the
attach/detach_client() callbacks will be called from outside of the
notifier chain's read section.

Introduce a mutex to protect access to the aliased_addrs list and its
underlying hardware table.

Signed-off-by: Romain Gantois <romain.gantois@bootlin.com>
---
drivers/media/i2c/ds90ub960.c | 23 ++++++++++++++++++++---
1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/drivers/media/i2c/ds90ub960.c b/drivers/media/i2c/ds90ub960.c
index 7534ddf2079fef466d3a114f0be98599427639fa..0510427ac4e9214132bcdf3fa18873ec78c48a5e 100644
--- a/drivers/media/i2c/ds90ub960.c
+++ b/drivers/media/i2c/ds90ub960.c
@@ -467,6 +467,8 @@ struct ub960_rxport {
};
} eq;

+ /* lock for aliased_addrs and associated registers */
+ struct mutex aliased_addrs_lock;
u16 aliased_addrs[UB960_MAX_PORT_ALIASES];
};

@@ -1030,6 +1032,9 @@ static int ub960_atr_attach_client(struct i2c_atr *atr, u32 chan_id,
struct ub960_rxport *rxport = priv->rxports[chan_id];
struct device *dev = &priv->client->dev;
unsigned int reg_idx;
+ int ret = 0;
+
+ mutex_lock(&rxport->aliased_addrs_lock);

for (reg_idx = 0; reg_idx < UB960_MAX_PORT_ALIASES; reg_idx++) {
if (!rxport->aliased_addrs[reg_idx])
@@ -1038,7 +1043,8 @@ static int ub960_atr_attach_client(struct i2c_atr *atr, u32 chan_id,

if (reg_idx == UB960_MAX_PORT_ALIASES) {
dev_err(dev, "rx%u: alias pool exhausted\n", rxport->nport);
- return -EADDRNOTAVAIL;
+ ret = -EADDRNOTAVAIL;
+ goto out_unlock;
}

rxport->aliased_addrs[reg_idx] = client->addr;
@@ -1051,7 +1057,9 @@ static int ub960_atr_attach_client(struct i2c_atr *atr, u32 chan_id,
dev_dbg(dev, "rx%u: client 0x%02x assigned alias 0x%02x at slot %u\n",
rxport->nport, client->addr, alias, reg_idx);

- return 0;
+out_unlock:
+ mutex_unlock(&rxport->aliased_addrs_lock);
+ return ret;
}

static void ub960_atr_detach_client(struct i2c_atr *atr, u32 chan_id,
@@ -1062,6 +1070,8 @@ static void ub960_atr_detach_client(struct i2c_atr *atr, u32 chan_id,
struct device *dev = &priv->client->dev;
unsigned int reg_idx;

+ mutex_lock(&rxport->aliased_addrs_lock);
+
for (reg_idx = 0; reg_idx < UB960_MAX_PORT_ALIASES; reg_idx++) {
if (rxport->aliased_addrs[reg_idx] == client->addr)
break;
@@ -1070,7 +1080,7 @@ static void ub960_atr_detach_client(struct i2c_atr *atr, u32 chan_id,
if (reg_idx == UB960_MAX_PORT_ALIASES) {
dev_err(dev, "rx%u: client 0x%02x is not mapped!\n",
rxport->nport, client->addr);
- return;
+ goto out_unlock;
}

rxport->aliased_addrs[reg_idx] = 0;
@@ -1079,6 +1089,9 @@ static void ub960_atr_detach_client(struct i2c_atr *atr, u32 chan_id,

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

static const struct i2c_atr_ops ub960_atr_ops = {
@@ -3181,6 +3194,8 @@ static void ub960_rxport_free_ports(struct ub960_data *priv)
fwnode_handle_put(rxport->source.ep_fwnode);
fwnode_handle_put(rxport->ser.fwnode);

+ mutex_destroy(&rxport->aliased_addrs_lock);
+
kfree(rxport);
priv->rxports[nport] = NULL;
}
@@ -3401,6 +3416,8 @@ static int ub960_parse_dt_rxport(struct ub960_data *priv, unsigned int nport,
if (ret)
goto err_put_remote_fwnode;

+ mutex_init(&rxport->aliased_addrs_lock);
+
return 0;

err_put_remote_fwnode:

--
2.47.1