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Date: Thu, 17 Mar 2016 17:04:30 -0700
From: Andrew Duggan <andrew.duggan@...il.com>
To: Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc: Wolfram Sang <wsa@...-dreams.de>, Jonathan Corbet <corbet@....net>,
Corey Minyard <minyard@....org>,
Jean Delvare <jdelvare@...e.com>,
Guenter Roeck <linux@...ck-us.net>,
Dmitry Torokhov <dmitry.torokhov@...il.com>,
Andrew Duggan <aduggan@...aptics.com>,
Christopher Heiny <cheiny@...aptics.com>,
linux-i2c@...r.kernel.org, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org,
linux-input <linux-input@...r.kernel.org>
Subject: Re: [PATCH v6 2/4] i2c-smbus: add SMBus Host Notify support
On Wed, Mar 16, 2016 at 9:39 AM, Benjamin Tissoires
<benjamin.tissoires@...hat.com> wrote:
> SMBus Host Notify allows a slave device to act as a master on a bus to
> notify the host of an interrupt. On Intel chipsets, the functionality
> is directly implemented in the firmware. We just need to export a
> function to call .alert() on the proper device driver.
>
> i2c_handle_smbus_host_notify() behaves like i2c_handle_smbus_alert().
> When called, it schedules a task that will be able to sleep to go through
> the list of devices attached to the adapter.
>
> The current implementation allows one Host Notification to be scheduled
> while an other is running.
>
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
Tested-by: Andrew Duggan <aduggan@...aptics.com>
> ---
>
> changes in v2:
> - do the actual processing of finding the device in i2c-smbus.c
> - remove the i2c-core implementations
> - remove the manual toggle of SMBus Host Notify
>
> no changes in v3
>
> changes in v4:
> - schedule the worker in i2c_handle_smbus_host_notify() -> it can now be called
> in an interrupt context.
> - introduce i2c_setup_smbus_host_notify()
>
> no changes in v5
>
> changes in v6:
> - fix the parameters of the inlined functions when the module is not compiled
>
> Documentation/i2c/smbus-protocol | 3 ++
> drivers/i2c/i2c-smbus.c | 113 +++++++++++++++++++++++++++++++++++++--
> include/linux/i2c-smbus.h | 44 +++++++++++++++
> include/linux/i2c.h | 3 ++
> include/uapi/linux/i2c.h | 1 +
> 5 files changed, 159 insertions(+), 5 deletions(-)
>
> diff --git a/Documentation/i2c/smbus-protocol b/Documentation/i2c/smbus-protocol
> index 6012b12..4e07848 100644
> --- a/Documentation/i2c/smbus-protocol
> +++ b/Documentation/i2c/smbus-protocol
> @@ -199,6 +199,9 @@ alerting device's address.
>
> [S] [HostAddr] [Wr] A [DevAddr] A [DataLow] A [DataHigh] A [P]
>
> +I2C drivers for devices which can trigger SMBus Host Notify should implement
> +the optional alert() callback.
> +
>
> Packet Error Checking (PEC)
> ===========================
> diff --git a/drivers/i2c/i2c-smbus.c b/drivers/i2c/i2c-smbus.c
> index 3b6765a..1de7ee5 100644
> --- a/drivers/i2c/i2c-smbus.c
> +++ b/drivers/i2c/i2c-smbus.c
> @@ -33,7 +33,8 @@ struct i2c_smbus_alert {
>
> struct alert_data {
> unsigned short addr;
> - u8 flag:1;
> + enum i2c_alert_protocol type;
> + unsigned int data;
> };
>
> /* If this is the alerting device, notify its driver */
> @@ -56,8 +57,7 @@ static int smbus_do_alert(struct device *dev, void *addrp)
> if (client->dev.driver) {
> driver = to_i2c_driver(client->dev.driver);
> if (driver->alert)
> - driver->alert(client, I2C_PROTOCOL_SMBUS_ALERT,
> - data->flag);
> + driver->alert(client, data->type, data->data);
> else
> dev_warn(&client->dev, "no driver alert()!\n");
> } else
> @@ -97,8 +97,9 @@ static void smbus_alert(struct work_struct *work)
> if (status < 0)
> break;
>
> - data.flag = status & 1;
> + data.data = status & 1;
> data.addr = status >> 1;
> + data.type = I2C_PROTOCOL_SMBUS_ALERT;
>
> if (data.addr == prev_addr) {
> dev_warn(&ara->dev, "Duplicate SMBALERT# from dev "
> @@ -106,7 +107,7 @@ static void smbus_alert(struct work_struct *work)
> break;
> }
> dev_dbg(&ara->dev, "SMBALERT# from dev 0x%02x, flag %d\n",
> - data.addr, data.flag);
> + data.addr, data.data);
>
> /* Notify driver for the device which issued the alert */
> device_for_each_child(&ara->adapter->dev, &data,
> @@ -240,6 +241,108 @@ int i2c_handle_smbus_alert(struct i2c_client *ara)
> }
> EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert);
>
> +static void smbus_host_notify_work(struct work_struct *work)
> +{
> + struct alert_data alert;
> + struct i2c_adapter *adapter;
> + unsigned long flags;
> + u16 payload;
> + u8 addr;
> + struct smbus_host_notify *data;
> +
> + data = container_of(work, struct smbus_host_notify, work);
> +
> + spin_lock_irqsave(&data->lock, flags);
> + payload = data->payload;
> + addr = data->addr;
> + adapter = data->adapter;
> +
> + /* clear the pending bit and release the spinlock */
> + data->pending = false;
> + spin_unlock_irqrestore(&data->lock, flags);
> +
> + if (!adapter || !addr)
> + return;
> +
> + alert.type = I2C_PROTOCOL_SMBUS_HOST_NOTIFY;
> + alert.addr = addr;
> + alert.data = payload;
> +
> + device_for_each_child(&adapter->dev, &alert, smbus_do_alert);
> +}
> +
> +/**
> + * i2c_setup_smbus_host_notify - Allocate a new smbus_host_notify for the given
> + * I2C adapter.
> + * @adapter: the adapter we want to associate a Host Notify function
> + *
> + * Returns a struct smbus_host_notify pointer on success, and NULL on failure.
> + * The resulting smbus_host_notify must not be freed afterwards, it is a
> + * managed resource already.
> + */
> +struct smbus_host_notify *i2c_setup_smbus_host_notify(struct i2c_adapter *adap)
> +{
> + struct smbus_host_notify *host_notify;
> +
> + host_notify = devm_kzalloc(&adap->dev, sizeof(struct smbus_host_notify),
> + GFP_KERNEL);
> + if (!host_notify)
> + return NULL;
> +
> + host_notify->adapter = adap;
> +
> + spin_lock_init(&host_notify->lock);
> + INIT_WORK(&host_notify->work, smbus_host_notify_work);
> +
> + return host_notify;
> +}
> +EXPORT_SYMBOL_GPL(i2c_setup_smbus_host_notify);
> +
> +/**
> + * i2c_handle_smbus_host_notify - Forward a Host Notify event to the correct
> + * I2C client.
> + * @host_notify: the struct host_notify attached to the relevant adapter
> + * @data: the Host Notify data which contains the payload and address of the
> + * client
> + * Context: can't sleep
> + *
> + * Helper function to be called from an I2C bus driver's interrupt
> + * handler. It will schedule the Host Notify work, in turn calling the
> + * corresponding I2C device driver's alert function.
> + *
> + * host_notify should be a valid pointer previously returned by
> + * i2c_setup_smbus_host_notify().
> + */
> +int i2c_handle_smbus_host_notify(struct smbus_host_notify *host_notify,
> + unsigned short addr, unsigned int data)
> +{
> + unsigned long flags;
> + struct i2c_adapter *adapter;
> +
> + if (!host_notify || !host_notify->adapter)
> + return -EINVAL;
> +
> + adapter = host_notify->adapter;
> +
> + spin_lock_irqsave(&host_notify->lock, flags);
> +
> + if (host_notify->pending) {
> + spin_unlock_irqrestore(&host_notify->lock, flags);
> + dev_warn(&adapter->dev, "Host Notify already scheduled\n.");
> + return -EFAULT;
> + }
> +
> + host_notify->payload = data;
> + host_notify->addr = addr;
> +
> + /* Mark that there is a pending notification and release the lock */
> + host_notify->pending = true;
> + spin_unlock_irqrestore(&host_notify->lock, flags);
> +
> + return schedule_work(&host_notify->work);
> +}
> +EXPORT_SYMBOL_GPL(i2c_handle_smbus_host_notify);
> +
> module_i2c_driver(smbalert_driver);
>
> MODULE_AUTHOR("Jean Delvare <jdelvare@...e.de>");
> diff --git a/include/linux/i2c-smbus.h b/include/linux/i2c-smbus.h
> index 8f1b086..3adeee3 100644
> --- a/include/linux/i2c-smbus.h
> +++ b/include/linux/i2c-smbus.h
> @@ -23,6 +23,8 @@
> #define _LINUX_I2C_SMBUS_H
>
> #include <linux/i2c.h>
> +#include <linux/spinlock.h>
> +#include <linux/workqueue.h>
>
>
> /**
> @@ -48,4 +50,46 @@ struct i2c_client *i2c_setup_smbus_alert(struct i2c_adapter *adapter,
> struct i2c_smbus_alert_setup *setup);
> int i2c_handle_smbus_alert(struct i2c_client *ara);
>
> +/**
> + * smbus_host_notify - internal structure used by the Host Notify mechanism.
> + * @adapter: the I2C adapter associated with this struct
> + * @work: worker used to schedule the IRQ in the slave device
> + * @lock: spinlock to check if a notification is already pending
> + * @pending: flag set when a notification is pending (any new notification will
> + * be rejected if pending is true)
> + * @payload: the actual payload of the Host Notify event
> + * @addr: the address of the slave device which raised the notification
> + *
> + * This struct needs to be allocated by i2c_setup_smbus_host_notify() and does
> + * not need to be freed. Internally, i2c_setup_smbus_host_notify() uses a
> + * managed resource to clean this up when the adapter get released.
> + */
> +struct smbus_host_notify {
> + struct i2c_adapter *adapter;
> + struct work_struct work;
> + spinlock_t lock;
> + bool pending;
> + u16 payload;
> + u8 addr;
> +};
> +
> +#if defined(CONFIG_I2C_SMBUS) || defined(CONFIG_I2C_SMBUS_MODULE)
> +struct smbus_host_notify *i2c_setup_smbus_host_notify(struct i2c_adapter *adap);
> +int i2c_handle_smbus_host_notify(struct smbus_host_notify *host_notify,
> + unsigned short addr, unsigned int data);
> +#else
> +static inline struct smbus_host_notify *
> +i2c_setup_smbus_host_notify(struct i2c_adapter *adap)
> +{
> + return NULL;
> +}
> +
> +static inline int
> +i2c_handle_smbus_host_notify(struct smbus_host_notify *host_notify,
> + unsigned short addr, unsigned int data)
> +{
> + return 0;
> +}
> +#endif /* I2C_SMBUS */
> +
> #endif /* _LINUX_I2C_SMBUS_H */
> diff --git a/include/linux/i2c.h b/include/linux/i2c.h
> index baae02a..056f800 100644
> --- a/include/linux/i2c.h
> +++ b/include/linux/i2c.h
> @@ -128,6 +128,7 @@ i2c_smbus_read_i2c_block_data_or_emulated(const struct i2c_client *client,
>
> enum i2c_alert_protocol {
> I2C_PROTOCOL_SMBUS_ALERT,
> + I2C_PROTOCOL_SMBUS_HOST_NOTIFY,
> };
>
> /**
> @@ -184,6 +185,8 @@ struct i2c_driver {
> * The format and meaning of the data value depends on the protocol.
> * For the SMBus alert protocol, there is a single bit of data passed
> * as the alert response's low bit ("event flag").
> + * For the SMBus Host Notify protocol, the data corresponds to the
> + * 16-bit payload data reported by the slave device acting as master.
> */
> void (*alert)(struct i2c_client *, enum i2c_alert_protocol protocol,
> unsigned int data);
> diff --git a/include/uapi/linux/i2c.h b/include/uapi/linux/i2c.h
> index b0a7dd6..83ec8ae 100644
> --- a/include/uapi/linux/i2c.h
> +++ b/include/uapi/linux/i2c.h
> @@ -101,6 +101,7 @@ struct i2c_msg {
> #define I2C_FUNC_SMBUS_WRITE_BLOCK_DATA 0x02000000
> #define I2C_FUNC_SMBUS_READ_I2C_BLOCK 0x04000000 /* I2C-like block xfer */
> #define I2C_FUNC_SMBUS_WRITE_I2C_BLOCK 0x08000000 /* w/ 1-byte reg. addr. */
> +#define I2C_FUNC_SMBUS_HOST_NOTIFY 0x10000000
>
> #define I2C_FUNC_SMBUS_BYTE (I2C_FUNC_SMBUS_READ_BYTE | \
> I2C_FUNC_SMBUS_WRITE_BYTE)
> --
> 2.5.0
>
> --
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