From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8427B44CAFE for ; Tue, 20 Jan 2026 18:12:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.19 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768932732; cv=none; b=PqoWOOHA5WMJ4TOpj0ThEQ3hqkNDjLT90ptrrmQJ2FtD65R3G6s1pHnvahhskcKUX2BYwv+0kzwrQVf7BkL6icQTPKR1yB5lzEsmF5eQUXZWtMmNN1e8klnfXZPCovC6ivqqDkL9Tdk8qHgO+4JgRB6LALjIC8lJM81V9xquEXk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768932732; c=relaxed/simple; bh=2ioqgKNJG4CDvzxiwQUNry8NcuvtGhb3/JxGfrs5Ma8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=uMlI6EkfG4tI43hS/w1JZm9YItKHeERpIjAf7SMk787MNZRQd5ZZDKXzR/tQCGtgHhA2WPSpjjaGHQ2cYA0W65PCwlY3JlGazIJ8rQGzU5MZdgOArZK/d3uQnvDEXZZ0FHaDJc1ogoaMWRBpn8qaQVmwBNZ4Cfta0s8vrqbzlj4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=JQ9OYISh; arc=none smtp.client-ip=198.175.65.19 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="JQ9OYISh" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1768932730; x=1800468730; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=2ioqgKNJG4CDvzxiwQUNry8NcuvtGhb3/JxGfrs5Ma8=; b=JQ9OYIShuB32qx74jrbFol0h6/W4v76I575Bi0OP6EsI224ywxwfmBfa qnl0akGvnG8sclgNWUA4C/IvQ9Q9ApNB8n+kymtQJ8oT9lqXHdWh3xe3g 9UQV1dcFgmkPV4T6cnHT5Pz8cSMhKs2L1WkN/jnaTUz0sSqnz1pnGXpzr E0p/dTpwkYMSJGcOZmQc+6nqi3XNlk5xExDmNc3hw8S6RI4c6+FIxshFT rYkQZx8L0kLzFaR5VUan7V9z+RFFO/SYGCn4Tq74qt2y+9kxM+W1UpfE6 4IGjMNiH+1yCTv0evJrZhdkmo2rB2Na7yxlSK4cpbQpvFLkd995vyPkMR g==; X-CSE-ConnectionGUID: eJ+o9eLaRwe0gz9SqT6oFA== X-CSE-MsgGUID: s8IO8CtsT8WOLd/yNNTS1Q== X-IronPort-AV: E=McAfee;i="6800,10657,11677"; a="70055588" X-IronPort-AV: E=Sophos;i="6.21,241,1763452800"; d="scan'208";a="70055588" Received: from orviesa009.jf.intel.com ([10.64.159.149]) by orvoesa111.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Jan 2026 10:12:09 -0800 X-CSE-ConnectionGUID: BEsc7aPPRDK7W0ypL/VmAg== X-CSE-MsgGUID: Mz59BMsORYeoPS6npeZ7yg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.21,241,1763452800"; d="scan'208";a="205997440" Received: from abityuts-desk.ger.corp.intel.com (HELO mnyman-desk.home) ([10.245.244.215]) by orviesa009-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Jan 2026 10:12:08 -0800 From: Mathias Nyman To: Cc: , =?UTF-8?q?=C5=81ukasz=20Bartosik?= , Mathias Nyman Subject: [PATCH 2/4] xhci: dbc: allow setting device serial number through sysfs Date: Tue, 20 Jan 2026 20:11:46 +0200 Message-ID: <20260120181148.128712-3-mathias.nyman@linux.intel.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260120181148.128712-1-mathias.nyman@linux.intel.com> References: <20260120181148.128712-1-mathias.nyman@linux.intel.com> Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Łukasz Bartosik Add dbc_serial sysfs attribute to allow changing the serial number string descriptor presented by the debug device when a host requests a string descriptor with iSerialNumber index. Value can only be changed while debug capability (DbC) is in disabled state to prevent USB device descriptor change while connected to a USB host. The default value is "0001". The field length can be from 1 to 126 characters. String is terminated at null or newline, driver does not support empty string. [ mn: Improve commit message and sysfs entry documentation ] Signed-off-by: Łukasz Bartosik Signed-off-by: Mathias Nyman --- .../testing/sysfs-bus-pci-drivers-xhci_hcd | 15 ++++++++ drivers/usb/host/xhci-dbgcap.c | 36 +++++++++++++++++++ 2 files changed, 51 insertions(+) diff --git a/Documentation/ABI/testing/sysfs-bus-pci-drivers-xhci_hcd b/Documentation/ABI/testing/sysfs-bus-pci-drivers-xhci_hcd index fc82aa4e54b0..b0e8ded09c16 100644 --- a/Documentation/ABI/testing/sysfs-bus-pci-drivers-xhci_hcd +++ b/Documentation/ABI/testing/sysfs-bus-pci-drivers-xhci_hcd @@ -85,3 +85,18 @@ Description: up to 5000. The default value is 64 ms. This polling interval is used while DbC is enabled but has no active data transfers. + +What: /sys/bus/pci/drivers/xhci_hcd/.../dbc_serial +Date: January 2026 +Contact: Łukasz Bartosik +Description: + The dbc_serial attribute allows to change the serial number + string descriptor presented by the debug device when a host + requests a string descriptor with iSerialNumber index. + Index is found in the iSerialNumber field in the device + descriptor. + Value can only be changed while debug capability (DbC) is in + disabled state to prevent USB device descriptor change while + connected to a USB host. + The default value is "0001". + The field length can be from 1 to 126 characters. diff --git a/drivers/usb/host/xhci-dbgcap.c b/drivers/usb/host/xhci-dbgcap.c index 4ba8edb37e51..a78d386ffdc3 100644 --- a/drivers/usb/host/xhci-dbgcap.c +++ b/drivers/usb/host/xhci-dbgcap.c @@ -1210,6 +1210,40 @@ static ssize_t dbc_bcdDevice_store(struct device *dev, return size; } +static ssize_t dbc_serial_show(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + struct xhci_hcd *xhci = hcd_to_xhci(dev_get_drvdata(dev)); + struct xhci_dbc *dbc = xhci->dbc; + + return sysfs_emit(buf, "%s\n", dbc->str.serial); +} + +static ssize_t dbc_serial_store(struct device *dev, + struct device_attribute *attr, + const char *buf, size_t size) +{ + struct xhci_hcd *xhci = hcd_to_xhci(dev_get_drvdata(dev)); + struct xhci_dbc *dbc = xhci->dbc; + size_t len; + + if (dbc->state != DS_DISABLED) + return -EBUSY; + + len = strcspn(buf, "\n"); + if (!len) + return -EINVAL; + + if (len > USB_MAX_STRING_LEN) + return -E2BIG; + + memcpy(dbc->str.serial, buf, len); + dbc->str.serial[len] = '\0'; + + return size; +} + static ssize_t dbc_bInterfaceProtocol_show(struct device *dev, struct device_attribute *attr, char *buf) @@ -1297,6 +1331,7 @@ static DEVICE_ATTR_RW(dbc); static DEVICE_ATTR_RW(dbc_idVendor); static DEVICE_ATTR_RW(dbc_idProduct); static DEVICE_ATTR_RW(dbc_bcdDevice); +static DEVICE_ATTR_RW(dbc_serial); static DEVICE_ATTR_RW(dbc_bInterfaceProtocol); static DEVICE_ATTR_RW(dbc_poll_interval_ms); @@ -1305,6 +1340,7 @@ static struct attribute *dbc_dev_attrs[] = { &dev_attr_dbc_idVendor.attr, &dev_attr_dbc_idProduct.attr, &dev_attr_dbc_bcdDevice.attr, + &dev_attr_dbc_serial.attr, &dev_attr_dbc_bInterfaceProtocol.attr, &dev_attr_dbc_poll_interval_ms.attr, NULL -- 2.43.0