On Wed, Nov 25, 2009 at 02:54:16PM +0530, Mandeep Sandhu wrote: > On Wed, Nov 25, 2009 at 1:33 PM, Rajaram R <rajaram.officemail@xxxxxxxxx> wrote: > > On Wed, Nov 25, 2009 at 3:30 PM, Mandeep Sandhu > > <mandeepsandhu.chd@xxxxxxxxx> wrote: > >> Hi All, > >> > >> I have a basic doubt on root hubs. > >> > >> I'm working on a media SoC which has 1 USB interface which can > >> function both as a host and a device (would this qualify for OTG? the > >> datasheet doesn't mention OTG though) and an on-chip PHY. Here's an > >> excerpt from the datasheet about the USB host controller: > >> > >> "The USB 2.0 Embedded Host Controller is fully compliant with the USB > >> 2.0 specification and the Enhanced Host Controller Interface (EHCI) > >> specification revision 1.0. The controller supports high-speed > >> (480Mbps) transfers. The controller comprehends the high-speed, > >> full-speed and low-speed data ranges providing compatibility with a > >> full range of USB devices. The full-speed and low-speed operations are > >> supported through the EHCI software stack via a transaction > >> translation layer." > >> > >> Now my question is, does the EHCI also function as a root hub? As in > >> the root hub is incorporated into the host controller? > >> > >> If I have to add another USB port to such a device, will it be > >> possible to connect it to the existing root hub? > >> > >> I'm asking this because its mentioned that the host controller also > >> has an on-chip PHY, and as I understand I'll have to connect my second > >> port directly onto the USB bus and not to the PHY interface. Is my > >> understanding correct? > > > > Can you point to the data sheet ? > > Can't, since it's not available in the public domain. > > Does the USB spec mandate that a host controller also function as a root hub? > (http://en.wikipedia.org/wiki/Usb#Overview) Why not read the USB spec yourself at www.usb.org to find out? :) thanks, greg k-h -- 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
