Subject: Re: [RFC PATCH 2/2] mmc: add OpenFirmware bindings for the mmc_spi driver

From: Jochen Friedrich <[email-masked]>
Date: Sat, 24 May 2008 16:32:48 +0200

Hi Grant,

>> +      - compatible : should be "linux,mmc-spi".
>> +      - linux,modalias  - should be "of_mmc_spi".
> 
> I'm not even sure if the whole linux,modalias is even a good idea.  I
> had kind of thrown it in there as a convenient way to override
> compatible when needed, but I haven't really thought it out very well
> and I think it is rather a hack.
> 
> The real problem is we don't yet have good method (or place) to apply
> a translation table from compatible values to modaliases.  Ideally,
> the translations should be part of the drivers themselves, but that
> causes a chicken and egg problem of needing to load the driver to get
> access to the table to know if it is the correct driver... Of course,
> I'm really not very familiar with the whole module autoloading
> mechanism.  Regardless; binding should be based on compatible, not on
> a hacky and bogus linux,modalias property.

i2c exactly has the same problem. Here the compatible entry is used
in drivers/of/of_i2c.c and mangled into a name to be used as modalias.
It's still sort of hackish, but it seems to be a compromise acceptable
by both OF and i2c folks.

Thanks,
Jochen