SMBus Host-Notify protocol, from the adapter point of view
consist of receiving a message from a client, including the
client address and some other data.
It can be simply handled by creating a new slave device
and registering a callback performing the parsing of the
message received from the client.
This commit introduces two new core functions
* i2c_new_smbus_host_notify_device
* i2c_free_smbus_host_notify_device
that take care of registration of the new slave device and
callback and will call i2c_handle_smbus_host_notify once a
Host-Notify event is received.
Signed-off-by: Alain Volmat <[email protected]>
---
v2: remove useless dev_err message in case of hnotify handling error
prevent handling hnotify in case of a incomplete write
drivers/i2c/i2c-core-smbus.c | 110 +++++++++++++++++++++++++++++++++++++++++++
include/linux/i2c-smbus.h | 2 +
2 files changed, 112 insertions(+)
diff --git a/drivers/i2c/i2c-core-smbus.c b/drivers/i2c/i2c-core-smbus.c
index 56bb840142e3..3a37664fb5f6 100644
--- a/drivers/i2c/i2c-core-smbus.c
+++ b/drivers/i2c/i2c-core-smbus.c
@@ -708,3 +708,113 @@ int of_i2c_setup_smbus_alert(struct i2c_adapter *adapter)
}
EXPORT_SYMBOL_GPL(of_i2c_setup_smbus_alert);
#endif
+
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+struct i2c_smbus_host_notify_status {
+ bool notify_start;
+ u8 addr;
+};
+
+static int i2c_smbus_host_notify_cb(struct i2c_client *client,
+ enum i2c_slave_event event, u8 *val)
+{
+ struct i2c_smbus_host_notify_status *status = client->dev.platform_data;
+ int ret;
+
+ switch (event) {
+ case I2C_SLAVE_WRITE_REQUESTED:
+ status->notify_start = true;
+ break;
+ case I2C_SLAVE_WRITE_RECEIVED:
+ /* We only retrieve the first byte received (addr)
+ * since there is currently no support to retrieve the data
+ * parameter from the client.
+ */
+ if (!status->notify_start)
+ break;
+ status->addr = *val;
+ status->notify_start = false;
+ break;
+ case I2C_SLAVE_STOP:
+ /* In case of incomplete write, don't handle host-notify */
+ if (status->notify_start) {
+ status->notify_start = false;
+ break;
+ }
+
+ ret = i2c_handle_smbus_host_notify(client->adapter,
+ status->addr);
+ if (ret < 0)
+ return ret;
+ break;
+ default:
+ /* Only handle necessary events */
+ break;
+ }
+
+ return 0;
+}
+
+/**
+ * i2c_new_smbus_host_notify_device - get a client for SMBus host-notify support
+ * @adapter: the target adapter
+ * Context: can sleep
+ *
+ * Setup handling of the SMBus host-notify protocol on a given I2C bus segment.
+ *
+ * Handling is done by creating a device and its callback and handling data
+ * received via the SMBus host-notify address (0x8)
+ *
+ * This returns the client, which should be ultimately freed using
+ * i2c_free_smbus_host_notify_device(); or an ERRPTR to indicate an error.
+ */
+struct i2c_client *i2c_new_smbus_host_notify_device(struct i2c_adapter *adapter)
+{
+ struct i2c_board_info host_notify_board_info = {
+ I2C_BOARD_INFO("smbus_host_notify", 0x08),
+ .flags = I2C_CLIENT_SLAVE,
+ };
+ struct i2c_smbus_host_notify_status *status;
+ struct i2c_client *client;
+ int ret;
+
+ status = kzalloc(sizeof(struct i2c_smbus_host_notify_status),
+ GFP_KERNEL);
+ if (!status)
+ return ERR_PTR(-ENOMEM);
+
+ host_notify_board_info.platform_data = status;
+
+ client = i2c_new_client_device(adapter, &host_notify_board_info);
+ if (IS_ERR(client)) {
+ kfree(status);
+ return client;
+ }
+
+ ret = i2c_slave_register(client, i2c_smbus_host_notify_cb);
+ if (ret) {
+ i2c_unregister_device(client);
+ kfree(status);
+ return ERR_PTR(ret);
+ }
+
+ return client;
+}
+EXPORT_SYMBOL_GPL(i2c_new_smbus_host_notify_device);
+
+/**
+ * i2c_free_smbus_host_notify_device - free the client for SMBus host-notify
+ * support
+ * @client: the client to free
+ * Context: can sleep
+ *
+ * Free the i2c_client allocated via i2c_new_smbus_host_notify_device
+ */
+void i2c_free_smbus_host_notify_device(struct i2c_client *client)
+{
+ i2c_slave_unregister(client);
+ kfree(client->dev.platform_data);
+ i2c_unregister_device(client);
+}
+EXPORT_SYMBOL_GPL(i2c_free_smbus_host_notify_device);
+#endif
diff --git a/include/linux/i2c-smbus.h b/include/linux/i2c-smbus.h
index 1e4e0de4ef8b..974038a684ed 100644
--- a/include/linux/i2c-smbus.h
+++ b/include/linux/i2c-smbus.h
@@ -38,6 +38,8 @@ static inline int of_i2c_setup_smbus_alert(struct i2c_adapter *adap)
return 0;
}
#endif
+struct i2c_client *i2c_new_smbus_host_notify_device(struct i2c_adapter *adapter);
+void i2c_free_smbus_host_notify_device(struct i2c_client *client);
#if IS_ENABLED(CONFIG_I2C_SMBUS) && IS_ENABLED(CONFIG_DMI)
void i2c_register_spd(struct i2c_adapter *adap);
--
2.7.4
On Thu, Jun 25, 2020 at 09:39:26AM +0200, Alain Volmat wrote:
> SMBus Host-Notify protocol, from the adapter point of view
> consist of receiving a message from a client, including the
> client address and some other data.
>
> It can be simply handled by creating a new slave device
> and registering a callback performing the parsing of the
> message received from the client.
>
> This commit introduces two new core functions
> * i2c_new_smbus_host_notify_device
> * i2c_free_smbus_host_notify_device
> that take care of registration of the new slave device and
> callback and will call i2c_handle_smbus_host_notify once a
> Host-Notify event is received.
>
> Signed-off-by: Alain Volmat <[email protected]>
> ---
> v2: remove useless dev_err message in case of hnotify handling error
> prevent handling hnotify in case of a incomplete write
Okay, now I got it to work, I also noted a few more issues.
First, I'd suggest s/i2c_smbus_host_notify/i2c_slave_host_notify/g for
all occurences in this patch. This makes a stronger distinction between
the generic HostNotify support and the slave specific one.
Also, I wonder if this shouldn't go to i2c-smbus.c instead but I haven't
checked if we end up in dependency hell then. Second best thought: at
least move to i2c-core-slave.c, then we could save the #ifdeffery in the
c-file?
>
> drivers/i2c/i2c-core-smbus.c | 110 +++++++++++++++++++++++++++++++++++++++++++
> include/linux/i2c-smbus.h | 2 +
> 2 files changed, 112 insertions(+)
>
> diff --git a/drivers/i2c/i2c-core-smbus.c b/drivers/i2c/i2c-core-smbus.c
> index 56bb840142e3..3a37664fb5f6 100644
> --- a/drivers/i2c/i2c-core-smbus.c
> +++ b/drivers/i2c/i2c-core-smbus.c
> @@ -708,3 +708,113 @@ int of_i2c_setup_smbus_alert(struct i2c_adapter *adapter)
> }
> EXPORT_SYMBOL_GPL(of_i2c_setup_smbus_alert);
> #endif
> +
> +#if IS_ENABLED(CONFIG_I2C_SLAVE)
> +struct i2c_smbus_host_notify_status {
> + bool notify_start;
> + u8 addr;
> +};
> +
> +static int i2c_smbus_host_notify_cb(struct i2c_client *client,
> + enum i2c_slave_event event, u8 *val)
> +{
> + struct i2c_smbus_host_notify_status *status = client->dev.platform_data;
> + int ret;
> +
> + switch (event) {
> + case I2C_SLAVE_WRITE_REQUESTED:
> + status->notify_start = true;
> + break;
> + case I2C_SLAVE_WRITE_RECEIVED:
> + /* We only retrieve the first byte received (addr)
> + * since there is currently no support to retrieve the data
> + * parameter from the client.
> + */
> + if (!status->notify_start)
> + break;
> + status->addr = *val;
> + status->notify_start = false;
So, we are safe if the message is too short. Otherwise, we capture the
first byte (== address) only, right. Further bytes until STOP are
discarded. So, we don't check if the message is too long and contains
more than the status word. Maybe we should add that?
> + break;
> + case I2C_SLAVE_STOP:
> + /* In case of incomplete write, don't handle host-notify */
> + if (status->notify_start) {
> + status->notify_start = false;
> + break;
> + }
> +
> + ret = i2c_handle_smbus_host_notify(client->adapter,
> + status->addr);
> + if (ret < 0)
> + return ret;
> + break;
> + default:
The missing cases are mandatory. From my testunit driver:
case I2C_SLAVE_READ_REQUESTED:
case I2C_SLAVE_READ_PROCESSED:
*val = 0xff;
break;
> + /* Only handle necessary events */
> + break;
> + }
> +
> + return 0;
> +}
> +
...
> --- a/include/linux/i2c-smbus.h
> +++ b/include/linux/i2c-smbus.h
> @@ -38,6 +38,8 @@ static inline int of_i2c_setup_smbus_alert(struct i2c_adapter *adap)
> return 0;
> }
> #endif
> +struct i2c_client *i2c_new_smbus_host_notify_device(struct i2c_adapter *adapter);
> +void i2c_free_smbus_host_notify_device(struct i2c_client *client);
Those need to be guarded with I2C_SLAVE as well. And an #else branch
with empty/successful placeholders.
>
> #if IS_ENABLED(CONFIG_I2C_SMBUS) && IS_ENABLED(CONFIG_DMI)
> void i2c_register_spd(struct i2c_adapter *adap);
> --
> 2.7.4
>
Hi Wolfram,
> Okay, now I got it to work, I also noted a few more issues.
>
> First, I'd suggest s/i2c_smbus_host_notify/i2c_slave_host_notify/g for
> all occurences in this patch. This makes a stronger distinction between
> the generic HostNotify support and the slave specific one.
Ok with that.
> Also, I wonder if this shouldn't go to i2c-smbus.c instead but I haven't
> checked if we end up in dependency hell then. Second best thought: at
> least move to i2c-core-slave.c, then we could save the #ifdeffery in the
> c-file?
I have actually difficulties to understand clearly what should go within
i2c-smbus.c vs i2c-core-smbus or i2c-core-slave. My feeling is that
i2c-core-slave is more about the registering of a slave rather than one usage
of the slave mechanism. Hence I am not sure those functions/cb belong there.
But at the same time, I don't know about i2c-smbus vs i2c-core-smbus. I putted
it within i2c-core-smbus considering that the creation of the alert device
is also done there.
....
> > +{
> > + struct i2c_smbus_host_notify_status *status = client->dev.platform_data;
> > + int ret;
> > +
> > + switch (event) {
> > + case I2C_SLAVE_WRITE_REQUESTED:
> > + status->notify_start = true;
> > + break;
> > + case I2C_SLAVE_WRITE_RECEIVED:
> > + /* We only retrieve the first byte received (addr)
> > + * since there is currently no support to retrieve the data
> > + * parameter from the client.
> > + */
> > + if (!status->notify_start)
> > + break;
> > + status->addr = *val;
> > + status->notify_start = false;
>
> So, we are safe if the message is too short. Otherwise, we capture the
> first byte (== address) only, right. Further bytes until STOP are
> discarded. So, we don't check if the message is too long and contains
> more than the status word. Maybe we should add that?
Yes I modified that.
> > + break;
> > + case I2C_SLAVE_STOP:
> > + /* In case of incomplete write, don't handle host-notify */
> > + if (status->notify_start) {
> > + status->notify_start = false;
> > + break;
> > + }
> > +
> > + ret = i2c_handle_smbus_host_notify(client->adapter,
> > + status->addr);
> > + if (ret < 0)
> > + return ret;
> > + break;
> > + default:
>
> The missing cases are mandatory. From my testunit driver:
>
> case I2C_SLAVE_READ_REQUESTED:
> case I2C_SLAVE_READ_PROCESSED:
> *val = 0xff;
> break;
Ok, done as well.
> > --- a/include/linux/i2c-smbus.h
> > +++ b/include/linux/i2c-smbus.h
> > @@ -38,6 +38,8 @@ static inline int of_i2c_setup_smbus_alert(struct i2c_adapter *adap)
> > return 0;
> > }
> > #endif
> > +struct i2c_client *i2c_new_smbus_host_notify_device(struct i2c_adapter *adapter);
> > +void i2c_free_smbus_host_notify_device(struct i2c_client *client);
>
> Those need to be guarded with I2C_SLAVE as well. And an #else branch
> with empty/successful placeholders.
Ok understood.