Re: [PATCH v3 05/13] i2c: acpi: Return error pointers from i2c_acpi_new_device()

Hans de Goede
2018-11-27T19:30:46Z

Hi,

On 27-11-18 20:27, Andy Shevchenko wrote:
> On Tue, Nov 27, 2018 at 05:14:06PM +0100, Hans de Goede wrote:
>> On 27-11-18 16:37, Andy Shevchenko wrote:
>>> The caller would like to know the reason why the i2c_acpi_new_device() fails.
>>> For example, if adapter is not available, it might be in the future and we
>>> would like to re-probe the clients again. But at the same time we would like to
>>> bail out if the error seems unrecoverable, such as invalid argument supplied.
>>> To achieve this, return error pointer in some cases.
>
>>> acpi_dev_free_resource_list(&resource_list);
>>> - if (ret < 0 || !info->addr)
>>> - return NULL;
>>> + if (!info->addr)
>>> + return ERR_PTR(-EADDRNOTAVAIL);
>>> adapter = i2c_acpi_find_adapter_by_handle(lookup.adapter_handle);
>>> if (!adapter)
>>> - return NULL;
>>> + return ERR_PTR(-ENODEV);
>
>> Why not simply return -EPROBE_DEFER here (and simplify the callers a lot).
>
>> This is the only case where we really want to defer.
>
>>> + client = i2c_new_device(adapter, info);
>>> + if (!client)
>>> + return ERR_PTR(-ENODEV);
>>
>> If you look at i2c_new_device, it can fail because it is
>> out of memory, the i2c slave address is invalid, or
>> their already is an i2c slave with the same address,
>> iow if this were to return an ERR_PTR itself, this
>> would return -ENOMEM, -EINVAL or -EBUSY and never
>> -EPROBE_DEFER.
>
> It would change the behaviour.

Yes it would change behaviour, for the better, all the errors
from i2c_new_device() (*) will not go away when we retry later,
so responding with probe-deferring to them is not useful.

> In any case, it's only two users and both written by you, so, just to be sure
> you aware of this change and bless it.

I'm aware and you've my ack for this change.

Regards,

Hans

*) with exception of -ENOMEM which should never happen