Request review of device tree documentation
grant.likely at secretlab.ca
Thu Sep 2 02:19:25 EST 2010
On Thu, Aug 05, 2010 at 02:43:25PM +1000, David Gibson wrote:
> On Fri, Jun 11, 2010 at 04:59:46PM -0600, Grant Likely wrote:
> > I've been doing a bit of work on some introductory level documentation
> > of the flattened device tree. I've got a rough copy up on the
> > devicetree.org wiki, and I could use some feedback. If anyone has
> > some time to look at it, you can find it here:
> > http://devicetree.org/Device_Tree_Usage
> Sorry I haven't replied sooner, I've been away, then sick and
> generally preoccupied. Still here are some comments now.
Thanks David. Reworked as per comments. You can see the diff here:
> How Addressing Works:
> * Small inconsistency you use "address1", "address2" then "unit-address3".
> * Perhaps re-emphasise that a parent's #*-cells properties govern the
> children's reg properties, not its own, since this is a common
> Non Memory Mapped Devices:
> * Your phrasing here suggests that non-memory-maped == zero
> size-cells, which is not always true.
> Ranges (Address Translation):
> * Third paragraph, first sentence is a grammatical dogs' breakfast,
> How Interrupts Work:
> * Bogus paragraph break partway through first sentence.
> * At the end you say the second cell indicates the interrupt's
> polarity, but you don't specify how this is encoded. It might be
> worth emphasising that while most interrupt specifiers do include
> trigger and polarity type information, the encoding of it can and
> does vary between interrupt controllers.
> Advanced Sample Machine:
> * The unit address in the name shouldn't have a "0x" prefix
> Advanced Interrupt Mapping:
> * Perhaps worth noting that while a PCI *card* will use INTA..INTD,
> on-board PCI devices can, and frequently do, have interrupts wired
> side-band to the PCI bus, directly to the main interrupt
> * In your example, you're muddying the waters of your previous usage
> of interrupt-parent. The PCI child nodes have the PCI top-level
> node as their implicit interrupt parent, because its their first
> ancestor with an interrupt-map, and we hit that before the
> interrupt-parent property specified at the very top level. This
> means amongst other things that if there are PCI devices with
> seperately wired interrupts, they must explicitly set
> interrupt-parent to bypass the normal PCI interrupt mapping.
> David Gibson | I'll have my music baroque, and my code
> david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
> | _way_ _around_!
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