From 13eef6a87a718876bf33d6fe1a947f8972362470 Mon Sep 17 00:00:00 2001
From: Sebastian Sumpf <sebastian.sumpf@genode-labs.com>
Date: Thu, 13 Feb 2025 11:57:54 +0100
Subject: [PATCH] genode_c_api/usb: fix size calculation of isoc_payload

simplify and fix wrong calculation of 'size' for isoc_payload.
---
 repos/os/src/lib/genode_c_api/usb.cc | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/repos/os/src/lib/genode_c_api/usb.cc b/repos/os/src/lib/genode_c_api/usb.cc
index 3645f88a9a..5f7defab7a 100644
--- a/repos/os/src/lib/genode_c_api/usb.cc
+++ b/repos/os/src/lib/genode_c_api/usb.cc
@@ -813,13 +813,15 @@ Interface_component::_handle_request(Constructible<Packet_descriptor> &cpd,
 		{
 			genode_usb_isoc_transfer_header & hdr =
 				*reinterpret_cast<genode_usb_isoc_transfer_header*>(payload.addr);
+
+			size_t const header_size = sizeof(genode_usb_isoc_transfer_header) +
+			                           (hdr.number_of_packets *
+			                           sizeof(genode_usb_isoc_descriptor));
+
 			genode_buffer_t isoc_payload {
-				(void*) ((addr_t)payload.addr +
-				         sizeof(genode_usb_isoc_transfer_header) +
-				         (hdr.number_of_packets *
-				          sizeof(genode_usb_isoc_descriptor))),
-				payload.size - sizeof(genode_usb_isoc_transfer_header) +
-				hdr.number_of_packets * sizeof(genode_usb_isoc_descriptor) };
+				(void *)(addr_t(payload.addr) + header_size),
+				payload.size - header_size };
+
 			cbs->isoc_fn(handle, cpd->index, hdr.number_of_packets,
 			             hdr.packets, isoc_payload, opaque_data);
 			break;