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SubjectRe: [PATCH v7 1/4] i2c-smbus : Add client discovered ARA support
On Sat, 13 Jan 2018 14:37:02 +0100
Marc CAPDEVILLE <m.capdeville@no-log.org> wrote:

> 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().

A trivial comment inline...

Also, I think this whole thing could do with some documentation as it is
a little 'unusual' :)

Perhaps put a cover letter explaining how whole series has changed as
well.

Jonathan

>
> Signed-off-by: Marc CAPDEVILLE <m.capdeville@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
> + /* 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 <jdelvare@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)
>

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