On Tuesday 24 March 2009, Martin Fuzzey wrote:
> The i.MX21 has a built in root hub and 3 ports, however depending on
> the board layout, only some of the ports may be accessible.
> When only some ports are available should GetHubDescriptor still
> indicate 3? [I presume so as other drivers do this]
> But in this case I just shouldn't activate the inaccessible ports - correct?
It's simplest to return "3" rather than try any kind of
remapping ("only port 3 works, remap it as port 1") or
even just shrinking "3" ("only port 1 works, report it
as only having 1 port"). If something happens on the
other ports, you'd have to cope with it anyway.
What you do with those ports is somewhat SOC-specific.
If "activating" has any side effects, don't; but if you
can avoid such special-casing, save the effort.
> Furthermore there are two host only ports and one port that can be
> configured as host / function / OTG.
> Will OTG support be required before merging the hcd driver? (once all
> the host only problems are fixed obviously)
No. In fact you *really* really want to get host support
working well before you touch OTG support.
> I currently know next to nothing about OTG in general and the linux
> implementation in particular. I've looked at drivers/usb/otg but the
> isp1301 tranceiver (which my board uses) code is mixed up with omap.
Yes. Somewhere in my mailbox I have patch from someone
at TI to split that driver in the middle, following some
kind of CEA-standardized version of the ISP1301 model.
Right now, that's the most functional OTG support in
Linux, and it's a bit specific to certain chip versions.
As in, OMAP1611b ... but not OMAP1710, which updated the
OTG controller.
> If possible I would prefer to get the hcd driver merged before looking
> at OTG. Are the any special things to be aware of to make later
> addition of OTG go smoothly?
Just be prepared for a bit of black magic needing to
get stirred into the mix. :)
The framework level interfaces are sort of OK, but a
lot of the interactions between drivers are more on
the custom-to-this-hardware level. So far. That's
obviously not the best way to be, long term.
- Dave
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