On 16/07/14 15:08, Arnd Bergmann wrote:
On Wednesday 16 July 2014 18:42:22 Jassi Brar wrote:
On 16 July 2014 18:39, Arnd Bergmann <arnd@xxxxxxxx> wrote:
On Wednesday 16 July 2014 18:35:33 Jassi Brar wrote:
On 16 July 2014 18:15, Arnd Bergmann <arnd@xxxxxxxx> wrote:
On Wednesday 16 July 2014 18:07:04 Jassi Brar wrote:
On 16 July 2014 15:46, Arnd Bergmann <arnd@xxxxxxxx> wrote:
On Wednesday 16 July 2014 10:40:19 Sudeep Holla wrote:
+
+Required property:
+- mbox: List of phandle and mailbox channel specifier.
+
+- mbox-names: List of identifier strings for each mailbox channel
+ required by the client.
+
IMO the mailbox names are more associated with the controller channels/
mailbox rather than the clients using it. Does it make sense to move
this under controller. It also avoid each client replicating the names.
I think it would be best to just make the mbox-names property optional,
like we have for other subsystems.
A very similar subsystem - DMAEngine also has 'dma-names' as a
required property.
If a client is assigned only 1 mbox in DT, we can do without
mbox-names. But I am not sure what to do if a client needs two or more
differently capable mboxes? Simply allocating in order of mbox request
doesn't seem very robust.
Traditionally, these things (regs, interrupts, ...) are just accessed
by index. The reason why dmaengine requires the name is that some machines
can use multiple DMA engine devices attached to the same request line,
so the dmaengine subsystem can pick any of them that has a matching
name.
And also, I think, when a client needs 2 different dma channels, say
for RX and TX each. The api can't assign the first channel specified
in 'dmas' property to the first channel request that comes to it,
unless we assume client driver always requests dma channels in the
order written in its DT node. And this is the main reason I see for
having mbox-names property.
Most subsystems require passing an explicit index in this case.
If we make mbox-names optional, do we assume client driver must
request mbox in the order specified in its DT node?
Correct.
OK. So how about we drop mbox-names altogether and expect client
driver to simply provide an index of the mbox needed?
That would be fine with me, but I think a lot of people like
the idea of identifying things by name, and are used to that
from the other subsystems.
Maybe you can leave the mbox-names property defined as 'optional'
in the generic mbox binding but remove the code in Linux? That way
we can always put it back at a later point without changing the
binding in an incompatible way.
Individual mailbox clients can mandate specific strings.
This sounds reasonable to me.
Regards,
Sudeep
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