Pinmux with device tree

[Nicolas Pitre]

On Thu, 19 May 2011, Mitch Bradley wrote:

> On 5/19/2011 10:36 AM, Nicolas Pitre wrote:
> > On Thu, 19 May 2011, Mitch Bradley wrote:
> > 
> > > So, in my world, space is always an issue.
> > 
> > I'm guessing that in such a scenario you have the kernel stored
> > somewhere else, right?  You therefore simply have to store the FDT data
> > along with the kernel in that other location, and have your boot
> > firmware load an additional and relatively small file.
> 
> There is no stored FDT.  The firmware generates the device tree dynamically
> from a combination of static information and dynamic probing.
> 
> > 
> > It is very important that the DT data be updateable independently from
> > the firmware, just like the kernel is.  Ideally, the DT would indeed be
> > exported by the firmware, but that works only in theory.  In practice it
> > _will_ contain bugs that might be visible only after kernel development
> > has progressed, and therefore it is primordial to be able to update it
> > easily.  Hence in practice it is best if it is not exported/generated by
> > the firmware directly.
> 
> 
> In our world it works in practice.  We control the hardware, firmware, and OS
> releases.  In many cases, a firmware update is less expensive than an OS
> release by several orders of magnitude.

I don't think this can be said for ARM in general though.
This is where all the recent surge of activity around DT comes from.


Nicolas