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

[Hans de Goede <hdegoede@redhat.com>]

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