[PATCH] powerpc: Create "rom" (MTD) device prpmc2800
Sergei Shtylyov
sshtylyov at ru.mvista.com
Sun Jun 3 14:03:02 EDT 2007
Hello.
Segher Boessenkool wrote:
>>> If it's a flash, compatible should be the chip type, and maybe as a
>>> second entry, what type of flash protocol (amd, intel, cfi, ...) it's
>>> compatible.
>> As I've already (and repatedly) stated before,
> And you repeatedly got answers too, yet you choose
> to rehash this whole discussion again.
Not I have started it. And I have my reasons, too. :-)
>> this gets you *nothing* WRT
>> selecting the proper driver in the current Linux MTD subsystem.
> Which Linux driver to use is not something that should
> be (directly) communicated in a device tree -- even if
Bah... what's "name" and "compatible" properties are for then. Nobody's
talking about the direct match but making the task of selecting a proper
driver more complex by specifying the details that don't help (if not hinder)
the correct selection is certainly not a way to go.
> you take the position the device tree is a nice big
> configuration file for Linux, what if a new Linux flash
> subsystem shows up (or even simply a driver got renamed,
> etc.)
There is no direct match in *this* case (for an example of such, refer to
FSL "gianfar" nodes ;-).
> -- the device tree on your board doesn't necessarily
> change when your kernel version does.
Well, I'm not anticipating any changes either in this case...
>> What it
>> actually *needs* to know is flash mapping information,
> It needs to know what kind of flash it is, and how it
> is connected -- i.e., it needs to describe the hardware.
> How Linux then decides to use it is its own game, but
> at least the device tree puts all the information it
> could possibly need out there.
>> the CFI/JEDEC interface then can be deduced by probing
> Most of the time, sure. Not always.
That's the way the cookie crumbles in Linux MTD for now. It's *always*
detecting this by probing -- you only can say what [not] to probe.
>> -- so, this property ("ptobe-type"), although specified in
>> Documentation/powerpc/booting-without-of.txt, is optional.
> Who is talking about "probe-type"? We are talking about "compatible".
See my other mail where I've told why I don't consider your example of
this prop valid...
> Segher
WBR, Sergei
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