On 10/27/2017 03:20 PM, Marc CAPDEVILLE wrote:
> On asus T100, Capella cm3218 chip is implemented as ambiant light
> sensor. This chip expose an smbus ARA protocol device on standard
> address 0x0c. The chip is not functional before all alerts are
> acknowledged.
> On asus T100, this device is enumerated on ACPI bus and the description
> give tow I2C connection. The first is the connection to the ARA device
two
> and the second gives the real address of the device.
Is there a document somewhere describing what this ARA stuff is and how it
works? Is this "Project ARA"?
>
> So, on device probe,If the i2c address is the ARA address and the
> device is enumerated via acpi, we lookup for the real address in
> the ACPI resource list and change it in the client structure.
> if an interrupt resource is given, and only for cm3218 chip,
> we declare an smbus_alert device.
>
> Signed-off-by: Marc CAPDEVILLE <m.capdeville@xxxxxxxxxx>
[...]
> +/* Get the real i2c address from acpi resources */
> +static int cm3218_acpi_get_address(struct i2c_client *client)
> +{
> + int ret;
> + struct acpi_device *adev;
> + LIST_HEAD(res_list);
> + struct resource_entry *res_entry;
> + struct acpi_resource *ares;
> + struct acpi_resource_i2c_serialbus *sb;
> +
> + adev = ACPI_COMPANION(&client->dev);
> + if (!adev)
> + return -ENODEV;
> +
> + ret = acpi_dev_get_resources(adev,
> + &res_list,
> + cm3218_filter_i2c_address,
> + client);
> + if (ret < 0)
> + return ret;
> +
> + /* get first resource */
> + res_entry = list_entry(&res_list, struct resource_entry, node);
> + ares = (struct acpi_resource *)res_entry->res;
> + sb = &ares->data.i2c_serial_bus;
> +
> + /* set i2c address */
> + client->addr = sb->slave_address;
> + client->flags &= ~I2C_CLIENT_TEN;
I'm not convinced overwriting the address and flags is legal. Those are
owned by the I2C core and should be read-only in the client driver. Maybe
use i2c_new_dummy() to create a device for the new address?
> + if (sb->access_mode == ACPI_I2C_10BIT_MODE)
> + client->flags |= I2C_CLIENT_TEN;
> +
> + acpi_dev_free_resource_list(&res_list);
> +
> + return 0;
> +}
[...]
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