USB: core: Add eUSB2 descriptor and parsing in USB core

Add support for the 'eUSB2 Isochronous Endpoint Companion Descriptor'
introduced in the recent USB 2.0 specification 'USB 2.0 Double Isochronous
IN Bandwidth' ECN.

It allows embedded USB2 (eUSB2) devices to report and use higher bandwidths
for isochronous IN transfers in order to support higher camera resolutions
on the lid of laptops and tablets with minimal change to the USB2 protocol.

The motivation for expanding USB 2.0 is further clarified in an additional
Embedded USB2 version 2.0 (eUSB2v2) supplement to the USB 2.0
specification. It points out this is optimized for performance, power and
cost by using the USB 2.0 low-voltage, power efficient PHY and half-duplex
link for the asymmetric camera bandwidth needs, avoiding the costly and
complex full-duplex USB 3.x symmetric link and gigabit receivers.

eUSB2 devices that support the higher isochronous IN bandwidth and the new
descriptor can be identified by their device descriptor bcdUSB value of
0x0220

Co-developed-by: Amardeep Rai <amardeep.rai@intel.com>
Signed-off-by: Amardeep Rai <amardeep.rai@intel.com>
Signed-off-by: Kannappan R <r.kannappan@intel.com>
Co-developed-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/20250220141339.1939448-1-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c
index f7bf8d1de3adeb16a540ec5236726fc7b03517df..13bd4ec4ea5f7a6fef615b6f50b1acb3bbe44ba4 100644 (file)
--- a/drivers/usb/core/config.c
+++ b/drivers/usb/core/config.c
@@ -64,6 +64,37 @@ static void usb_parse_ssp_isoc_endpoint_companion(struct device *ddev,
        memcpy(&ep->ssp_isoc_ep_comp, desc, USB_DT_SSP_ISOC_EP_COMP_SIZE);
 }
 
+static void usb_parse_eusb2_isoc_endpoint_companion(struct device *ddev,
+               int cfgno, int inum, int asnum, struct usb_host_endpoint *ep,
+               unsigned char *buffer, int size)
+{
+       struct usb_eusb2_isoc_ep_comp_descriptor *desc;
+       struct usb_descriptor_header *h;
+
+       /*
+        * eUSB2 isochronous endpoint companion descriptor for this endpoint
+        * shall be declared before the next endpoint or interface descriptor
+        */
+       while (size >= USB_DT_EUSB2_ISOC_EP_COMP_SIZE) {
+               h = (struct usb_descriptor_header *)buffer;
+
+               if (h->bDescriptorType == USB_DT_EUSB2_ISOC_ENDPOINT_COMP) {
+                       desc = (struct usb_eusb2_isoc_ep_comp_descriptor *)buffer;
+                       ep->eusb2_isoc_ep_comp = *desc;
+                       return;
+               }
+               if (h->bDescriptorType == USB_DT_ENDPOINT ||
+                   h->bDescriptorType == USB_DT_INTERFACE)
+                       break;
+
+               buffer += h->bLength;
+               size -= h->bLength;
+       }
+
+       dev_notice(ddev, "No eUSB2 isoc ep %d companion for config %d interface %d altsetting %d\n",
+                  ep->desc.bEndpointAddress, cfgno, inum, asnum);
+}
+
 static void usb_parse_ss_endpoint_companion(struct device *ddev, int cfgno,
                int inum, int asnum, struct usb_host_endpoint *ep,
                unsigned char *buffer, int size)
@@ -258,8 +289,10 @@ static int usb_parse_endpoint(struct device *ddev, int cfgno,
        int n, i, j, retval;
        unsigned int maxp;
        const unsigned short *maxpacket_maxes;
+       u16 bcdUSB;
 
        d = (struct usb_endpoint_descriptor *) buffer;
+       bcdUSB = le16_to_cpu(udev->descriptor.bcdUSB);
        buffer += d->bLength;
        size -= d->bLength;
 
@@ -409,15 +442,17 @@ static int usb_parse_endpoint(struct device *ddev, int cfgno,
 
        /*
         * Validate the wMaxPacketSize field.
-        * Some devices have isochronous endpoints in altsetting 0;
-        * the USB-2 spec requires such endpoints to have wMaxPacketSize = 0
-        * (see the end of section 5.6.3), so don't warn about them.
+        * eUSB2 devices (see USB 2.0 Double Isochronous IN ECN 9.6.6 Endpoint)
+        * and devices with isochronous endpoints in altsetting 0 (see USB 2.0
+        * end of section 5.6.3) have wMaxPacketSize = 0.
+        * So don't warn about those.
         */
        maxp = le16_to_cpu(endpoint->desc.wMaxPacketSize);
-       if (maxp == 0 && !(usb_endpoint_xfer_isoc(d) && asnum == 0)) {
+
+       if (maxp == 0 && bcdUSB != 0x0220 &&
+           !(usb_endpoint_xfer_isoc(d) && asnum == 0))
                dev_notice(ddev, "config %d interface %d altsetting %d endpoint 0x%X has invalid wMaxPacketSize 0\n",
                    cfgno, inum, asnum, d->bEndpointAddress);
-       }
 
        /* Find the highest legal maxpacket size for this endpoint */
        i = 0;          /* additional transactions per microframe */
@@ -465,6 +500,12 @@ static int usb_parse_endpoint(struct device *ddev, int cfgno,
                                maxp);
        }
 
+       /* Parse a possible eUSB2 periodic endpoint companion descriptor */
+       if (bcdUSB == 0x0220 && d->wMaxPacketSize == 0 &&
+           (usb_endpoint_xfer_isoc(d) || usb_endpoint_xfer_int(d)))
+               usb_parse_eusb2_isoc_endpoint_companion(ddev, cfgno, inum, asnum,
+                                                       endpoint, buffer, size);
+
        /* Parse a possible SuperSpeed endpoint companion descriptor */
        if (udev->speed >= USB_SPEED_SUPER)
                usb_parse_ss_endpoint_companion(ddev, cfgno,

diff --git a/include/linux/usb.h b/include/linux/usb.h
index cfa8005e24f9fe7bc823e37250e1743969778731..b46738701f8dc46085f251379873b6a8a008d99d 100644 (file)
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -51,6 +51,7 @@ struct ep_device;
  * @desc: descriptor for this endpoint, wMaxPacketSize in native byteorder
  * @ss_ep_comp: SuperSpeed companion descriptor for this endpoint
  * @ssp_isoc_ep_comp: SuperSpeedPlus isoc companion descriptor for this endpoint
+ * @eusb2_isoc_ep_comp: eUSB2 isoc companion descriptor for this endpoint
  * @urb_list: urbs queued to this endpoint; maintained by usbcore
  * @hcpriv: for use by HCD; typically holds hardware dma queue head (QH)
  *     with one or more transfer descriptors (TDs) per urb
@@ -64,9 +65,10 @@ struct ep_device;
  * descriptor within an active interface in a given USB configuration.
  */
 struct usb_host_endpoint {
-       struct usb_endpoint_descriptor          desc;
-       struct usb_ss_ep_comp_descriptor        ss_ep_comp;
-       struct usb_ssp_isoc_ep_comp_descriptor  ssp_isoc_ep_comp;
+       struct usb_endpoint_descriptor                  desc;
+       struct usb_ss_ep_comp_descriptor                ss_ep_comp;
+       struct usb_ssp_isoc_ep_comp_descriptor          ssp_isoc_ep_comp;
+       struct usb_eusb2_isoc_ep_comp_descriptor        eusb2_isoc_ep_comp;
        struct list_head                urb_list;
        void                            *hcpriv;
        struct ep_device                *ep_dev;        /* For sysfs info */

diff --git a/include/uapi/linux/usb/ch9.h b/include/uapi/linux/usb/ch9.h
index 91f0f7e214a5a57c8bee3f44c4dbf7b175843d8c..475af9358173b0290cf945a763f87eefbe7d4cb1 100644 (file)
--- a/include/uapi/linux/usb/ch9.h
+++ b/include/uapi/linux/usb/ch9.h
@@ -253,6 +253,9 @@ struct usb_ctrlrequest {
 #define USB_DT_BOS                     0x0f
 #define USB_DT_DEVICE_CAPABILITY       0x10
 #define USB_DT_WIRELESS_ENDPOINT_COMP  0x11
+/* From the eUSB2 spec */
+#define USB_DT_EUSB2_ISOC_ENDPOINT_COMP        0x12
+/* From Wireless USB spec */
 #define USB_DT_WIRE_ADAPTER            0x21
 /* From USB Device Firmware Upgrade Specification, Revision 1.1 */
 #define USB_DT_DFU_FUNCTIONAL          0x21
@@ -675,6 +678,18 @@ static inline int usb_endpoint_interrupt_type(
 
 /*-------------------------------------------------------------------------*/
 
+/* USB_DT_EUSB2_ISOC_ENDPOINT_COMP: eUSB2 Isoch Endpoint Companion descriptor */
+struct usb_eusb2_isoc_ep_comp_descriptor {
+       __u8    bLength;
+       __u8    bDescriptorType;
+       __le16  wMaxPacketSize;
+       __le32  dwBytesPerInterval;
+} __attribute__ ((packed));
+
+#define USB_DT_EUSB2_ISOC_EP_COMP_SIZE 8
+
+/*-------------------------------------------------------------------------*/
+
 /* USB_DT_SSP_ISOC_ENDPOINT_COMP: SuperSpeedPlus Isochronous Endpoint Companion
  * descriptor
  */