From: Rai, Amardeep <amardeep.rai@intel.com>
Date: Wed, 20 Aug 2025 14:38:19 +0000 (+0300)
Subject: usb: core: Add a function to get USB version independent periodic payload
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=20f988320d2718ef28b1f0635acc88c12a216d29;p=users%2Fhch%2Fmisc.git

usb: core: Add a function to get USB version independent periodic payload

Add usb_endpoint_max_periodic_payload() to obtain maximum payload bytes in
a service interval for isochronous and interrupt 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>
Acked-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20250820143824.551777-5-sakari.ailus@linux.intel.com
---

diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index fca7735fc660..ca9ff6ad8e73 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -1110,6 +1110,35 @@ void usb_free_noncoherent(struct usb_device *dev, size_t size,
 }
 EXPORT_SYMBOL_GPL(usb_free_noncoherent);
 
+/**
+ * usb_endpoint_max_periodic_payload - Get maximum payload bytes per service
+ *				       interval
+ * @udev: The USB device
+ * @ep: The endpoint
+ *
+ * Returns: the maximum number of bytes isochronous or interrupt endpoint @ep
+ * can transfer during a service interval, or 0 for other endpoints.
+ */
+u32 usb_endpoint_max_periodic_payload(struct usb_device *udev,
+				      const struct usb_host_endpoint *ep)
+{
+	if (!usb_endpoint_xfer_isoc(&ep->desc) &&
+	    !usb_endpoint_xfer_int(&ep->desc))
+		return 0;
+
+	switch (udev->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);
+	default:
+		return usb_endpoint_maxp(&ep->desc) * usb_endpoint_maxp_mult(&ep->desc);
+	}
+}
+EXPORT_SYMBOL_GPL(usb_endpoint_max_periodic_payload);
+
 /*
  * Notifications of device and interface registration
  */
diff --git a/include/linux/usb.h b/include/linux/usb.h
index 9d662c6abb4d..e9cf2786d8bd 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -2039,6 +2039,9 @@ static inline u16 usb_maxpacket(struct usb_device *udev, int pipe)
 	return usb_endpoint_maxp(&ep->desc);
 }
 
+u32 usb_endpoint_max_periodic_payload(struct usb_device *udev,
+				      const struct usb_host_endpoint *ep);
+
 /* translate USB error codes to codes user space understands */
 static inline int usb_translate_errors(int error_code)
 {