Re: [PATCH 1/5] USB: Make usb_hcd_irq work for multi-role USB controllers w/ shared irq

On Friday 23 November 2007, Grant Likely wrote:

Some multi-role (host/peripheral) USB controllers use a shared interrupt
line for all parts of the chip.

Like the musb_hdrc code ... soonish to go upstream (it needs some
updates to catch up to usbcore urb->status changes), this is used
by the Nokia 800 and 810.  In terms of chips with Linux support:
DaVinci, TUSB60x0, OMAP 2430, OMAP 3430, Blackfin BF527; and ISTR
a few less-publicised ones (including, yes, some PPC SOCs).

That driver hasn't needed to change usbcore for IRQ handling though.

Export usb_hcd_irq so drivers can call it 
from their interrupt handler instead of duplicating code.

This seems to be the main point of this patch.  I'd rather just
make that "static" though; it should already be marked that way.

That routine doesn't do enough to make me like it any more; and
with dual-role controllers, the driver lifecycle is more complex
than usbcore can be expected to mediate.  Best to just call the
host side IRQ logic directly from your toplevel IRQ handler.

Drivers pass an irqnum of 0 to usb_add_hcd to signal that the interrupt handler
shouldn't be registerred by the core.

The current way to get that behavior is to leave hcd->driver->irq
as zero; then "irqnum" is ignored, and your dual role driver can
register its own handler.

- Dave