[PATCH 1/2] update crypto node definition and device tree instances
kim.phillips at freescale.com
Sat May 31 08:40:36 EST 2008
On Fri, 30 May 2008 23:28:38 +0200
Segher Boessenkool <segher at kernel.crashing.org> wrote:
> Nice cleanup! Just one thing...
> > + - compatible : Should contain entries for all compatible SEC
> > versions,
> > + high to low, e.g., "fsl,sec2.1", "fsl,sec2.0"
> *All* compatible versions? That's not really correct -- for
> example that would include *future* versions!
ok, so 'backward compatible'..
> The first entry should describe the exact device version. If
> there are more entries, they should be for device versions where
> the driver for that device version can be reasonably expected to
> do something useful with this newer device (reduced functionality,
> perhaps). Listing *all* compatible devices is a) infeasible,
> b) not useful, and c) insane :-)
> Say you have a 3.3 device, and all 3.x devices have the same
> programming interface; also, the 2.x interface works with reduced
> functionality, and 1.x isn't useful at all; in that case, you would
> list 3.3, 3.0, 2.0. The driver that knows about 3.x would probe
> for 3.0, while an older driver would probe for 2.0. The driver
> doesn't need to probe for 3.3, since devices implementing 3.3
> should show they are compatible with 3.0 (and the binding should
> say they should show this).
All the driver has to do to turn on a particular feature is call
of_device_is_compatible with the version string of the h/w version that
introduces that feature. In the above case, a driver wanting to use
e.g., hardware ICV checking, would have to check for 2.1 and 3.x instead
of just 2.1.
> Also, the binding should explicitly list all defined compatible
> entries (and what they mean), not just give a few examples.
I'm not sure I understand; a lot of the differences between the SEC
versions are miniscule feature bits scattered across the programming
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