Peter Chen <peter.chen@xxxxxxxxxxxxx> writes: > On Fri, Mar 15, 2013 at 05:17:08PM +0200, Alexander Shishkin wrote: >> >> > Eg, for tablet or phone, the dr_mode may be "gadget", but the >> > otg_capable = 1. >> >> No, because dr_mode indicates controller's capability, and not the >> "current" mode of operation. Why would anyone want to put *that* in a >> DT? >> > > OK, now I totally understand your mind of this problem. In fact, dr_mode > is NOT controller's capability, even at its original place: > (Documentation/devicetree/bindings/usb/fsl-usb.txt or nvidia, tegra20-ehci.txt) > dr_mode is the usb working mode. > > When we design USB system, the requirements are differ from products > to products. > The phone/tablet device may only wants itself as gadget > device, it needs to be no-response when there is a usb device plug in > (eg usb keyboard with Micro B-to-A cable). > > The car entertainment system or other Standard-A port system do not want > to be enumerated when it plugs to notebook using Standard A-to-A cable. Bah. Of course, you're right. We're stuck with dr_mode till people learn to design middleware stacks that can handle being both host and peripheral. > So, currently, even most of controllers are otg-capable, still most > of designs are one working mode designed. The reason why we design > the dr_mode is that we want controller working mode to be decided > by DT without re-compile the kernel by build out the host/gadget driver. Ok, so then how about introducing *one* more parameter, something like "dr_cap", which 1) when specified, supersedes DCCPARAMS, so no need to read that register any more; 2) when unspecified, use DCCPARAMS; 3) can be one of "host", "peripheral", "otg", "dual_role": - host, peripheral: initialize one role only, stick to that, no otg; - dual_role: initialize both roles, no otg; - otg: both roles, ci->is_otg == true. Another question now is, do we need "dual_role" variant for the dr_mode parameter? Regards, -- Alex -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
