Re: New USB stack on FreeBSD w/Linux emulation layer coming

On Thursday 17 May 2007 19:44, David Brownell wrote:
> On Thursday 17 May 2007, Hans Petter Selasky wrote:
> > I would like introduce a new USB API call, so that my pre-allocate model
> > will work better with your USB API. For example I want something like
> > this:
> >
> > void
> > usb_setup_endpoint(struct usb_device *usb, struct usb_interface *ui,
> > struct usb_host_endpoint *uhe, uint32_t bufsize, uint32_t unused0,
> > uint32_t unused1, uint32_t unused2);
>
> The usb_device and usb_interface are implied by the usb_host_endpoint,
> and "unused" parameters are pointless.  Sizes are "size_t", and such
> a call could obviously fail because of invalid parameters.   So
>
> 	int usb_setup_endpoint(struct usb_host_endpoint *hep, size_t bufsize);

To save the "hep" to "struct usb_device" pointer, I would like to have "struct 
usb_device *dev" as an argument. 

>
> What would such a call do, though?  Who would use it, and why?

The call will setup one or two pre-allocated USB transfers for the emulation 
layer between the Linux USB stack and the FreeBSD USB stack.

I've currently put the following into this function:

int32_t
usb_setup_endpoint(struct usb_device *dev, struct usb_host_endpoint *uhe, 
uint32_t bufsize)
{
        struct usbd_config cfg[2];
        uint16_t mfs = usbd_get_max_frame_size((usb_endpoint_descriptor_t 
*)&(uhe->desc));
        uint8_t type = uhe->desc.bmAttributes & UE_XFERTYPE;
        uint8_t addr = uhe->desc.bEndpointAddress;

        usbd_transfer_unsetup(uhe->bsd_xfer, 2);

        if (bufsize == 0) {
            return 0;
        }

        bzero(cfg, sizeof(cfg));

        if (type == UE_ISOCHRONOUS) {

            /* Isochronous is special */

            cfg[0].type = type;
            cfg[0].endpoint = addr & UE_ADDR;
            cfg[0].direction = addr & (UE_DIR_OUT|UE_DIR_IN);
            cfg[0].callback = &usb_linux_isoc_callback;
            cfg[0].bufsize = 0; /* use wMaxPacketSize */

            bcopy(cfg + 0, cfg + 1, sizeof(*cfg));

            if (usbd_transfer_setup(dev->bsd_udev, uhe->bsd_iface_index,
                                    uhe->bsd_xfer, cfg, 2, uhe, 
                                    &usb_global_lock))
            {
                return -EINVAL;
            }
        } else {
            if (bufsize > (1 << 22)) {
                /* limit buffer size */
                bufsize = (1 << 22);
            }

            if (type == UE_CONTROL) {
              /* we need enough room for the control header */
              if (bufsize < sizeof(usb_device_request_t)) {
                  bufsize = sizeof(usb_device_request_t);
              }
            }

            if (bufsize < mfs) {
                /* we need to be able to hold at least one frame! */
                bufsize = mfs;
            }

            cfg[0].type = type;
            cfg[0].endpoint = addr & UE_ADDR;
            cfg[0].direction = addr & (UE_DIR_OUT|UE_DIR_IN);
            cfg[0].callback = &usb_linux_non_isoc_callback;
            cfg[0].bufsize = bufsize;

            if (usbd_transfer_setup(dev->bsd_udev, uhe->bsd_iface_index,
                                    uhe->bsd_xfer, cfg, 1, uhe, 
                                    &usb_global_lock))
            {
                return -EINVAL;
            }
        }
        return 0;
}

The reason for this is to allow Linux USB drivers to tell the FreeBSD USB 
stack that they want larger/smaller buffers.

On Linux this information can be used to reserve EHCI/UHCI/OHCI USB transfer 
descriptors.

>
> > On FreeBSD this function will pre-allocate one or two USB transfers for
> > an endpoint using the given "bufsize" argument. Those FreeBSD USB
> > transfers will then be used to do all the Linux USB transfers. This
> > function can block and must have a context.
>
> So what's the model ... GPL'd Linux drivers will be modified to
> incorporate that call, so they'd work better on FreeBSD?

Yes, and under Linux.

As you can see, it is not possible to emulate an on-the-fly allocation model 
by a pre-allocation model. That's why I suggest this API addition.

--HPS

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