[SeaBIOS] questions about seabios ohci code

[Kevin O'Connor]

I'm CC'ing the mailing list.

On Wed, Apr 14, 2010 at 02:04:48AM +0800, Qing Pei Wang wrote:
> hi kevin,
>    i am learning the code of seabios/ohci stack followed with OHCI spec. I
> have some question.

Note that the OHCI support has only been tested on a modified qemu - I
haven't had any reports on real hardware.

> 1) in the function alloc_intr_pipe (usb.c line118)what does the frameexp
> mean?

It's log2(epdesc->bInterval) - the log of the sampling time (in ms)
requested by the device.

> 2) how does ohci get the intervals. the code just use epdesc->bInterval, how
> does it init? can pass the parameter from the usb-hid.c?

The epdesc structure is populated by get_device_config() - the config
read from the device includes the device config, interface
descriptions, and end point descriptions.

-Kevin