Re: [PATCH 1/4] i2c: smbus: add core function handling SMBus host-notify

Alain Volmat
2020-05-26T10:23:25Z

On Sat, May 23, 2020 at 10:46:25AM +0000, Wolfram Sang wrote:
>
> Adding Benjamin who mainly implemented this.
>
> On Tue, May 05, 2020 at 07:51:08AM +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.
>
> Yay, cool idea to use the slave interface. I like it a lot!
>
> > +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 way to retrieve the data
> > + * parameter from the client.
>
> Maybe s/no way/no support/ ? I still wonder if we couldn't add it
> somehow. Once we find a device which needs this, of course.

Indeed. Such support can be added later on once such device is found. For the
time being I will state "no support"

>
> > + */
> > + if (!status->notify_start)
> > + break;
> > + status->addr = *val;
> > + status->notify_start = false;
> > + break;
> > + case I2C_SLAVE_STOP:
>
> What about setting 'notify_start' to false here as well? In the case of
> an incomplete write?

Ok. I will check that notify_start is false before calling host_notify
(since otherwise it will call i2c_handle_smbus_host_notify with a bad addr
value) and reset notify_start to false if it is still true.

>
> > + ret = i2c_handle_smbus_host_notify(client->adapter,
> > + status->addr);
> > + if (ret < 0) {
> > + dev_warn(&client->adapter->dev, "failed to handle host_notify (%d)\n",
> > + ret);
>
> I think we should rather add such error strings to the core if we think
> they are needed. I am not convinced they are, though.

Agreed, this error can be removed.

>
> > + return ret;
> > + }
> > + break;
> > + default:
> > + /* Only handle necessary events */
> > + break;
> > + }
> > +
> > + return 0;
> > +}
> > +
>
> Rest of the code looks good. Maybe we should compile all this only when
> I2C_SLAVE is enabled?
>

Yes, I will enclose that around I2C_SLAVE support check.