Subject: Re: [PATCH] powerpc, 460gt: Add 460gt as compatible in the check for 460ex-compatible crypto

From: Segher Boessenkool <[email-masked]>
Date: Fri, 24 Jun 2011 04:14:07 +0200

>>> - =A0 =A0 =A0 if (of_find_compatible_node(NULL, NULL,=20
>>> "amcc,ppc460ex-crypto")) {
>>> + =A0 =A0 =A0 if (of_find_compatible_node(NULL, NULL,=20
>>> "amcc,ppc460ex-crypto") ||
>>> + =A0 =A0 =A0 =A0 =A0 of_find_compatible_node(NULL, NULL,=20
>>> "amcc,ppc460gt-crypto")) {
>>
>> If the device is actually compatible, the device tree node should=20
>> claim
>> it is, and you do not need this code change.
>
> That was actually my first instinct, however I tried to follow the
> current convention in the glacier and canyonlands DTS files, which is
> to set every device compatible to 460gt or 460ex, depending on the
> processor. Many of the devices are identical between the two, since
> they are variations of the same SoC, so which is the preferred method?
> Follow the device tree convention and add the compatibility check in
> the driver,

That is not the convention.

> or alter the device trees? I'll send another patch if it's
> the latter.

You say

   compatible =3D "amcc,ppc460gt-crypto", "amcc,ppc460ex-crypto";

So, a unique name for the actual device first, followed by the name of
what it is compatible to.  The driver for 460ex-crypto will then work
without any changes, but it can also do some 460gt-specific workarounds
or enhancements; or you could even have a totally separate driver for
the 460gt-crypto (you'll have to arrange for it to be used preferably
then).

You should document this 460gt-crypto binding, btw (a single line in
the 460ex-crypto binding doc will do).

Segher