Re: Pinmux with device tree

[Mitch Bradley <wmb-D5eQfiDGL7eakBO8gow8eQ@public.gmane.org>]

On 5/19/2011 4:23 PM, Nicolas Pitre wrote:
> 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.


Agreed, but I was pointing out that not everybody has space to burn, so 
I hope that the ultimate solution doesn't treat space as free.

>
>
> Nicolas
>