Re: [PATCH] i2c: do not acpi/of match device in i2c_device_probe()

[Sergey Senozhatsky]

On (20/08/26 23:49), Sergey Senozhatsky wrote:
> i2c, apparently, can match the same device twice - the first
> time in ->match bus hook (i2c_device_match()), and the second
> one in ->probe (i2c_device_probe()) bus hook.
> 
> To make things more complicated, the second matching does not
> do exactly same checks as the first one. Namely, i2c_device_match()
> calls acpi_driver_match_device() which considers devices that
> provide of_match_table and performs of_compatible() matching for
> such devices. One important thing to note here is that ACPI
> of_compatible() matching (acpi_of_match_device()) is part of ACPI
> and does not depend on CONFIG_OF.
> 
> i2c_device_probe(), on the other hand, calls acpi_match_device()
> which does not perform of_compatible() matching, but instead
> i2c_device_probe() relies on CONFIG_OF API to perform of_match_table
> matching, IOW ->probe matching, unlike ->match matching, depends on
> CONFIG_OF. This can break i2c device probing on !CONFIG_OF systems
> if the device does not provide .id_table.
> 
>  i2c_device_probe()
>  ...
>    if (!driver->id_table &&
>        !i2c_acpi_match_device(dev->driver->acpi_match_table, client) &&
>        !i2c_of_match_device(dev->driver->of_match_table, client)) {
>        status = -ENODEV;
>        goto put_sync_adapter;
>    }
> 
> i2c_of_match_device() on !CONFIG_OF systems is always false, so we never
> perform of_match_table matching. i2c_acpi_match_device() does ACPI match
> only, no of_compatible() matching takes place, even though the device
> provides .of_match_table and ACPI is capable of matching such device.
> 
> It is not entirely clear why the device is matched again in bus
> ->probe after successful and proper matching in bus ->match. Let's
> remove ->probe matching.

Hi,

Gentle ping.

	-ss