This is from rfc by Alan Cox : https://patchwork.ozlabs.org/patch/381773
The idea is as follows (extract from above rfc) :
- If an adapter knows about its ARA and smbus alerts then the adapter
creates its own interrupt handler as before
- If a client knows it needs smbus alerts it calls
i2c_require_smbus_alert(). This ensures that there is an ARA handler
registered and tells the client whether the adapter is handling it
anyway or not.
- When the client learns that an ARA event has occurred it calls
i2c_smbus_alert_event() which uses the existing ARA mechanism to kick
things off.
In addition, if a client have an irq line to trigger smbus alert, client
driver register its irq with i2c_smbus_alert_add_irq() to the smbus alert
driver to use the generic alert interrupt handler. On detach, the client
must unregister its irq from the smbus alert driver with
i2c_smbus_alert_free_irq().
Signed-off-by: Marc CAPDEVILLE <m.capdevi...@no-log.org>
---
drivers/i2c/i2c-core-smbus.c | 42 +++++++++++
drivers/i2c/i2c-smbus.c | 171 +++++++++++++++++++++++++++++++++++++++++--
include/linux/i2c-smbus.h | 22 ++++++
include/linux/i2c.h | 2 +
4 files changed, 232 insertions(+), 5 deletions(-)
diff --git a/drivers/i2c/i2c-core-smbus.c b/drivers/i2c/i2c-core-smbus.c
index 1238c94fe5a1..0d84ac9669e9 100644
--- a/drivers/i2c/i2c-core-smbus.c
+++ b/drivers/i2c/i2c-core-smbus.c
@@ -659,6 +659,48 @@ struct i2c_client *i2c_setup_smbus_alert(struct
i2c_adapter *adapter,
}
EXPORT_SYMBOL_GPL(i2c_setup_smbus_alert);
+/**
+ * i2c_require_smbus_alert - Client discovered SMBus alert
+ * @client: client requiring ARA support
+ *
+ * When a client needs an ARA it calls this method. If the bus adapter
+ * supports ARA and already knows how to do so then it will already have
+ * configured for ARA and this is a no-op. If not then we set up an ARA
+ * on the adapter.
+ *
+ * Return:
+ * 0 if ARA support already registered
+ * 1 if call register a new smbus_alert device
+ * <0 on error
+ */
+int i2c_require_smbus_alert(struct i2c_client *client)
+{
+ struct i2c_adapter *adapter = client->adapter;
+ struct i2c_smbus_alert_setup setup;
+ struct i2c_client *ara;
+ int ret;
+
+ if (adapter->smbus_ara) {
+ /*
+ * ARA is already known and handled by the adapter (ideal case)
+ * or another client has specified ARA is needed
+ */
+ ret = 0;
+ } else {
+ /* First client requesting alert and no adapter has
+ * has setup one
+ */
+ setup.irq = 0;
+ ara = i2c_setup_smbus_alert(adapter, &setup);
+ if (!ara)
+ return -ENODEV;
+ ret = 1;
+ }
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(i2c_require_smbus_alert);
+
#if IS_ENABLED(CONFIG_I2C_SMBUS) && IS_ENABLED(CONFIG_OF)
int of_i2c_setup_smbus_alert(struct i2c_adapter *adapter)
{
diff --git a/drivers/i2c/i2c-smbus.c b/drivers/i2c/i2c-smbus.c
index 5a1dd7f13bac..1699333ac950 100644
--- a/drivers/i2c/i2c-smbus.c
+++ b/drivers/i2c/i2c-smbus.c
@@ -25,9 +25,16 @@
#include <linux/slab.h>
#include <linux/workqueue.h>
+struct i2c_smbus_irq_usage {
+ struct list_head list;
+ int irq;
+ int count;
+};
+
struct i2c_smbus_alert {
struct work_struct alert;
struct i2c_client *ara; /* Alert response address */
+ struct list_head irq_usage; /* irq usage list */
};
struct alert_data {
@@ -126,6 +133,124 @@ static void smbalert_work(struct work_struct *work)
}
+/**
+ * i2c_smbus_alert_add_irq - Add a new irq handler to ARA client
+ * @client: The client which want to add an smbus alert irq handler
+ * @irq: The irq number to be added to the smbus alert device
+ * return: 0 if irq handler already exist, 1 if a new handler has been
+ * registered, <0 on error
+ *
+ * This is used by the smbalert_probe and by smbus client to check if an
+ * irq handler already exist for that irq and if not register a new one
+ * Clients must free their irq with i2c_smbus_alert_free_irq() on driver
+ * detach.
+ */
+int i2c_smbus_alert_add_irq(struct i2c_client *client, int irq)
+{
+ int res;
+ struct i2c_smbus_irq_usage *irq_usage;
+ struct i2c_client *ara;
+ struct i2c_smbus_alert *alert;
+
+ ara = client->adapter->smbus_ara;
+ if (!ara)
+ return -EINVAL;
+
+ alert = i2c_get_clientdata(client->adapter->smbus_ara);
+ if (!alert)
+ return -EINVAL;
+
+ if (!irq)
+ return 0;
+
+ /* Check if handler exist for that irq */
+ list_for_each_entry(irq_usage, &alert->irq_usage, list)
+ if (irq_usage->irq == irq)
+ break;
+
+ if (irq_usage->irq == irq) {
+ irq_usage->count++;
+ } else {
+ /* setup a new handler for that irq */
+ res = devm_request_threaded_irq(&ara->dev, irq,
+ NULL, smbus_alert,
+ IRQF_SHARED | IRQF_ONESHOT,
+ "smbus_alert", alert);
+ if (res)
+ return res;
+
+ /* Add adapter irq number to used irq list with a count of 1 */
+ irq_usage = devm_kmalloc(&ara->dev,
+ sizeof(struct i2c_smbus_irq_usage),
+ GFP_KERNEL);
+ INIT_LIST_HEAD(&irq_usage->list);
+ irq_usage->irq = irq;
+ irq_usage->count = 1;
+ list_add(&irq_usage->list, &alert->irq_usage);
+
+ return 0;
+ }
+
+ return 1;
+}
+EXPORT_SYMBOL_GPL(i2c_smbus_alert_add_irq);
+
+/**
+ * i2c_smbus_alert_free_irq - free irq added with i2c_smbus_alert_add_irq()
+ * @client: The client which want to free its smbus alert irq
+ * @irq: The irq number to be freed
+ * return: 0 if irq handler still exist for other client,
+ * 1 if client is the last one using this handler and handler have been
+ * removed,
+ * <0 on error.
+ *
+ * This is used by smbus clients to free their irq usage from smbus alert
+ * device.
+ */
+int i2c_smbus_alert_free_irq(struct i2c_client *client, int irq)
+{
+ struct i2c_smbus_irq_usage *irq_usage;
+ struct i2c_client *ara;
+ struct i2c_smbus_alert *alert;
+
+ ara = client->adapter->smbus_ara;
+ if (!ara)
+ return -EINVAL;
+
+ alert = i2c_get_clientdata(client->adapter->smbus_ara);
+ if (!alert)
+ return -EINVAL;
+
+ if (!irq)
+ return 0;
+
+ /* Check if handler exist for that irq */
+ list_for_each_entry(irq_usage, &alert->irq_usage, list)
+ if (irq_usage->irq == irq)
+ break;
+
+ if (irq_usage->irq == irq) {
+ irq_usage->count--;
+ if (!irq_usage->count) {
+ /* usage count goes to 0
+ * so remove irq_usage from list
+ */
+ list_del(&irq_usage->list);
+ devm_kfree(&ara->dev, irq_usage);
+
+ /* remove irq handler */
+ devm_free_irq(&ara->dev, irq, alert);
+
+ return 1;
+ }
+
+ return 0;
+ }
+
+ return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(i2c_smbus_alert_free_irq);
+
/* Setup SMBALERT# infrastructure */
static int smbalert_probe(struct i2c_client *ara,
const struct i2c_device_id *id)
@@ -151,16 +276,18 @@ static int smbalert_probe(struct i2c_client *ara,
INIT_WORK(&alert->alert, smbalert_work);
alert->ara = ara;
+ INIT_LIST_HEAD(&alert->irq_usage);
+
+ i2c_set_clientdata(ara, alert);
+
+ ara->adapter->smbus_ara = ara;
+
if (irq > 0) {
- res = devm_request_threaded_irq(&ara->dev, irq,
- NULL, smbus_alert,
- IRQF_SHARED | IRQF_ONESHOT,
- "smbus_alert", alert);
+ res = i2c_smbus_alert_add_irq(ara, irq);
if (res)
return res;
}
- i2c_set_clientdata(ara, alert);
dev_info(&adapter->dev, "supports SMBALERT#\n");
return 0;
@@ -172,6 +299,9 @@ static int smbalert_remove(struct i2c_client *ara)
struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
cancel_work_sync(&alert->alert);
+
+ ara->adapter->smbus_ara = NULL;
+
return 0;
}
@@ -210,6 +340,37 @@ int i2c_handle_smbus_alert(struct i2c_client *ara)
}
EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert);
+/**
+ * i2c_smbus_alert_event
+ * @client: the client who known of a probable ARA event
+ * Context: can't sleep
+ *
+ * Helper function to be called from an I2C device driver's interrupt
+ * handler. It will schedule the alert work, in turn calling the
+ * corresponding I2C device driver's alert function.
+ *
+ * It is assumed that client is an i2c client who previously call
+ * i2c_require_smbus_alert().
+ *
+ * return: <0 on error
+ */
+int i2c_smbus_alert_event(struct i2c_client *client)
+{
+ struct i2c_client *ara;
+ struct i2c_smbus_alert *alert;
+
+ ara = client->adapter->smbus_ara;
+ if (!ara)
+ return -EINVAL;
+
+ alert = i2c_get_clientdata(ara);
+ if (!alert)
+ return -EINVAL;
+
+ return schedule_work(&alert->alert);
+}
+EXPORT_SYMBOL_GPL(i2c_smbus_alert_event);
+
module_i2c_driver(smbalert_driver);
MODULE_AUTHOR("Jean Delvare <jdelv...@suse.de>");
diff --git a/include/linux/i2c-smbus.h b/include/linux/i2c-smbus.h
index fb0e040b1abb..cf777f29cc79 100644
--- a/include/linux/i2c-smbus.h
+++ b/include/linux/i2c-smbus.h
@@ -47,6 +47,7 @@ struct i2c_smbus_alert_setup {
struct i2c_client *i2c_setup_smbus_alert(struct i2c_adapter *adapter,
struct i2c_smbus_alert_setup *setup);
+int i2c_require_smbus_alert(struct i2c_client *client);
int i2c_handle_smbus_alert(struct i2c_client *ara);
#if IS_ENABLED(CONFIG_I2C_SMBUS) && IS_ENABLED(CONFIG_OF)
@@ -58,4 +59,25 @@ static inline int of_i2c_setup_smbus_alert(struct
i2c_adapter *adap)
}
#endif
+#if IS_ENABLED(CONFIG_I2C_SMBUS)
+int i2c_smbus_alert_add_irq(struct i2c_client *client, int irq);
+int i2c_smbus_alert_free_irq(struct i2c_client *client, int irq);
+int i2c_smbus_alert_event(struct i2c_client *client);
+#else
+static inline int i2c_smbus_alert_add_irq(struct i2c_client *client, int irq)
+{
+ return -EINVAL;
+}
+
+static inline int i2c_smbus_alert_free_irq(struct i2c_client *client, int irq)
+{
+ return -EINVAL;
+}
+
+static inline int i2c_smbus_alert_event(struct i2c_client *client)
+{
+ return -EINVAL;
+}
+#endif
+
#endif /* _LINUX_I2C_SMBUS_H */
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 5d7f3c1853ae..7592dce12923 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -652,6 +652,8 @@ struct i2c_adapter {
const struct i2c_adapter_quirks *quirks;
struct irq_domain *host_notify_domain;
+
+ struct i2c_client *smbus_ara; /* ARA client address if any or NULL */
};
#define to_i2c_adapter(d) container_of(d, struct i2c_adapter, dev)
--
2.11.0
