Re: [RFC PATCH v2 6/6] i2c: core: hand over reserved devices when requesting ancillary addresses

Luca Ceresoli
2020-04-15T10:07:55Z

Hi,

On 18/03/20 16:00, Wolfram Sang wrote:
> With i2c_new_ancillary_address, we can check if the intended driver is
> requesting a reserved address. Update the function to do these checks.
> If the check passes, the "reserved" device will become a regular "dummy"
> device.
>
> Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
> ---
> drivers/i2c/i2c-core-base.c | 24 ++++++++++++++++++++++--
> 1 file changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
> index 84464e439df5..81fb320de28d 100644
> --- a/drivers/i2c/i2c-core-base.c
> +++ b/drivers/i2c/i2c-core-base.c
> @@ -974,7 +974,9 @@ struct i2c_client *i2c_new_ancillary_device(struct i2c_client *client,
> const char *name,
> u16 default_addr)
> {
> - struct device_node *np = client->dev.of_node;
> + struct device_node *reserved_np, *np = client->dev.of_node;
> + struct device *reserved_dev, *adapter_dev = &client->adapter->dev;
> + struct i2c_client *reserved_client = NULL;
> u32 addr = default_addr;
> int i;
>
> @@ -984,7 +986,25 @@ struct i2c_client *i2c_new_ancillary_device(struct i2c_client *client,
> of_property_read_u32_index(np, "reg", i, &addr);
> }
>
> - dev_dbg(&client->adapter->dev, "Address for %s : 0x%x\n", name, addr);
> + dev_info(adapter_dev, "Address for %s : 0x%x\n", name, addr);

Here if we have two identical chips on the same bus, they probably will
both add an ancillary device with the same name. Then a message like:

i2c i2c-0: ds90ub954-q1: Address for rxport0: 0x40

won't tell which ds90ub954-q1 device is using that address. I'd rather
disambiguate using something like:

dev_info(adapter_dev, "%s: Address for %s: 0x%x\n",
dev_name(&client->dev), name, addr);

Sure, this issue did exist before this patch, but since the line is
being promoted from dbg to info (which is OK), it's probably a good idea
to improve the content, perhaps in a separate patch.

Except for that, I tested the patch and it's working fine.

--
Luca