On 03/20/2013 12:04 PM, Alexander Shishkin wrote: > 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? What's the difference between the newly proposed dr_cap and the dr_mode parameter? Marc -- Pengutronix e.K. | Marc Kleine-Budde | Industrial Linux Solutions | Phone: +49-231-2826-924 | Vertretung West/Dortmund | Fax: +49-5121-206917-5555 | Amtsgericht Hildesheim, HRA 2686 | http://www.pengutronix.de |
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