[PATCH v3 3/4] USB: Add a function to obtain USB version independent maximum bpi value

[Sakari Ailus <sakari.ailus@linux.intel.com>]

From: "Rai, Amardeep" <amardeep.rai@intel.com>

Add usb_endpoint_max_isoc_bpi() to obtain maximum bytes per interval for
isochronous endpoints in a USB version independent way.

Signed-off-by: Rai, Amardeep <amardeep.rai@intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Co-developed-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Hans de Goede <hansg@kernel.org>
---
 include/linux/usb.h | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/include/linux/usb.h b/include/linux/usb.h
index 535ac37198a1..da0f51dfe15f 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -2049,6 +2049,37 @@ static inline int usb_translate_errors(int error_code)
 	}
 }
 
+/**
+ * usb_endpoint_max_isoc_bpi - Get maximum isochronous transfer bytes per interval
+ * @dev: The USB device
+ * @ep: The endpoint
+ *
+ * Returns: the maximum number of bytes isochronous endpoint @endpoint can
+ * transfer in during a service interval, or 0 for non-isochronous endpoints.
+ */
+static inline u32 usb_endpoint_max_isoc_bpi(struct usb_device *dev,
+					    const struct usb_host_endpoint *ep)
+{
+	if (usb_endpoint_type(&ep->desc) != USB_ENDPOINT_XFER_ISOC)
+		return 0;
+
+	switch (dev->speed) {
+	case USB_SPEED_SUPER_PLUS:
+		if (USB_SS_SSP_ISOC_COMP(ep->ss_ep_comp.bmAttributes))
+			return le32_to_cpu(ep->ssp_isoc_ep_comp.dwBytesPerInterval);
+		fallthrough;
+	case USB_SPEED_SUPER:
+		return le16_to_cpu(ep->ss_ep_comp.wBytesPerInterval);
+	case USB_SPEED_HIGH:
+		if (ep->eusb2_isoc_ep_comp.bDescriptorType &&
+		    !usb_endpoint_maxp(&ep->desc) && usb_endpoint_dir_in(&ep->desc))
+			return le32_to_cpu(ep->eusb2_isoc_ep_comp.dwBytesPerInterval);
+		fallthrough;
+	default:
+		return usb_endpoint_maxp(&ep->desc) * usb_endpoint_maxp_mult(&ep->desc);
+	}
+}
+
 /* Events from the usb core */
 #define USB_DEVICE_ADD		0x0001
 #define USB_DEVICE_REMOVE	0x0002
-- 
2.39.5