* [PATCH 1/4] xhci: dbc: prepare to expose strings through sysfs
2026-01-20 18:11 [PATCH 0/4] xhci feature for usb-next Mathias Nyman
@ 2026-01-20 18:11 ` Mathias Nyman
2026-01-20 18:11 ` [PATCH 2/4] xhci: dbc: allow setting device serial number " Mathias Nyman
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: Mathias Nyman @ 2026-01-20 18:11 UTC (permalink / raw)
To: gregkh; +Cc: linux-usb, Łukasz Bartosik, Mathias Nyman
From: Łukasz Bartosik <ukaszb@chromium.org>
Reorganize the code to prepare ground for setting serial number,
product and manufacturer names through sysfs. This commit:
1. Introduces new buffers for storing serial number, product and
manufacturer name in utf8. The buffers will be used by sysfs
*_show and *_store functions.
2. Increases USB string descriptor data maximum length to the
value from USB specification (126 bytes of data).
3. Adds new helper functions get_str_desc_len, prepare_len
and xhci_dbc_populate_str_desc.
Signed-off-by: Łukasz Bartosik <ukaszb@chromium.org>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
---
drivers/usb/host/xhci-dbgcap.c | 151 ++++++++++++++++++---------------
drivers/usb/host/xhci-dbgcap.h | 39 ++++++---
2 files changed, 112 insertions(+), 78 deletions(-)
diff --git a/drivers/usb/host/xhci-dbgcap.c b/drivers/usb/host/xhci-dbgcap.c
index 9da4f3b452cb..4ba8edb37e51 100644
--- a/drivers/usb/host/xhci-dbgcap.c
+++ b/drivers/usb/host/xhci-dbgcap.c
@@ -29,6 +29,12 @@
#include "xhci-trace.h"
#include "xhci-dbgcap.h"
+static const struct dbc_str dbc_str_default = {
+ .manufacturer = "Linux Foundation",
+ .product = "Linux USB Debug Target",
+ .serial = "0001",
+};
+
static void dbc_free_ctx(struct device *dev, struct xhci_container_ctx *ctx)
{
if (!ctx)
@@ -52,55 +58,6 @@ static void dbc_ring_free(struct device *dev, struct xhci_ring *ring)
kfree(ring);
}
-static u32 xhci_dbc_populate_strings(struct dbc_str_descs *strings)
-{
- struct usb_string_descriptor *s_desc;
- u32 string_length;
-
- /* Serial string: */
- s_desc = (struct usb_string_descriptor *)strings->serial;
- utf8s_to_utf16s(DBC_STRING_SERIAL, strlen(DBC_STRING_SERIAL),
- UTF16_LITTLE_ENDIAN, (wchar_t *)s_desc->wData,
- DBC_MAX_STRING_LENGTH);
-
- s_desc->bLength = (strlen(DBC_STRING_SERIAL) + 1) * 2;
- s_desc->bDescriptorType = USB_DT_STRING;
- string_length = s_desc->bLength;
- string_length <<= 8;
-
- /* Product string: */
- s_desc = (struct usb_string_descriptor *)strings->product;
- utf8s_to_utf16s(DBC_STRING_PRODUCT, strlen(DBC_STRING_PRODUCT),
- UTF16_LITTLE_ENDIAN, (wchar_t *)s_desc->wData,
- DBC_MAX_STRING_LENGTH);
-
- s_desc->bLength = (strlen(DBC_STRING_PRODUCT) + 1) * 2;
- s_desc->bDescriptorType = USB_DT_STRING;
- string_length += s_desc->bLength;
- string_length <<= 8;
-
- /* Manufacture string: */
- s_desc = (struct usb_string_descriptor *)strings->manufacturer;
- utf8s_to_utf16s(DBC_STRING_MANUFACTURER,
- strlen(DBC_STRING_MANUFACTURER),
- UTF16_LITTLE_ENDIAN, (wchar_t *)s_desc->wData,
- DBC_MAX_STRING_LENGTH);
-
- s_desc->bLength = (strlen(DBC_STRING_MANUFACTURER) + 1) * 2;
- s_desc->bDescriptorType = USB_DT_STRING;
- string_length += s_desc->bLength;
- string_length <<= 8;
-
- /* String0: */
- strings->string0[0] = 4;
- strings->string0[1] = USB_DT_STRING;
- strings->string0[2] = 0x09;
- strings->string0[3] = 0x04;
- string_length += 4;
-
- return string_length;
-}
-
static void xhci_dbc_init_ep_contexts(struct xhci_dbc *dbc)
{
struct xhci_ep_ctx *ep_ctx;
@@ -124,7 +81,65 @@ static void xhci_dbc_init_ep_contexts(struct xhci_dbc *dbc)
ep_ctx->deq = cpu_to_le64(deq | dbc->ring_in->cycle_state);
}
-static void xhci_dbc_init_contexts(struct xhci_dbc *dbc, u32 string_length)
+static u8 get_str_desc_len(const char *desc)
+{
+ return ((struct usb_string_descriptor *)desc)->bLength;
+}
+
+static u32 dbc_prepare_info_context_str_len(struct dbc_str_descs *descs)
+{
+ u32 len;
+
+ len = get_str_desc_len(descs->serial);
+ len <<= 8;
+ len += get_str_desc_len(descs->product);
+ len <<= 8;
+ len += get_str_desc_len(descs->manufacturer);
+ len <<= 8;
+ len += get_str_desc_len(descs->string0);
+
+ return len;
+}
+
+static int xhci_dbc_populate_str_desc(char *desc, const char *src)
+{
+ struct usb_string_descriptor *s_desc;
+ int len;
+
+ s_desc = (struct usb_string_descriptor *)desc;
+
+ /* len holds number of 2 byte UTF-16 characters */
+ len = utf8s_to_utf16s(src, strlen(src), UTF16_LITTLE_ENDIAN,
+ (wchar_t *)s_desc->wData, USB_MAX_STRING_LEN * 2);
+ if (len < 0)
+ return len;
+
+ s_desc->bLength = len * 2 + 2;
+ s_desc->bDescriptorType = USB_DT_STRING;
+
+ return s_desc->bLength;
+}
+
+static void xhci_dbc_populate_str_descs(struct dbc_str_descs *str_descs,
+ struct dbc_str *str)
+{
+ /* Serial string: */
+ xhci_dbc_populate_str_desc(str_descs->serial, str->serial);
+
+ /* Product string: */
+ xhci_dbc_populate_str_desc(str_descs->product, str->product);
+
+ /* Manufacturer string: */
+ xhci_dbc_populate_str_desc(str_descs->manufacturer, str->manufacturer);
+
+ /* String0: */
+ str_descs->string0[0] = 4;
+ str_descs->string0[1] = USB_DT_STRING;
+ str_descs->string0[2] = 0x09;
+ str_descs->string0[3] = 0x04;
+}
+
+static void xhci_dbc_init_contexts(struct xhci_dbc *dbc)
{
struct dbc_info_context *info;
u32 dev_info;
@@ -135,12 +150,12 @@ static void xhci_dbc_init_contexts(struct xhci_dbc *dbc, u32 string_length)
/* Populate info Context: */
info = (struct dbc_info_context *)dbc->ctx->bytes;
- dma = dbc->string_dma;
+ dma = dbc->str_descs_dma;
info->string0 = cpu_to_le64(dma);
- info->manufacturer = cpu_to_le64(dma + DBC_MAX_STRING_LENGTH);
- info->product = cpu_to_le64(dma + DBC_MAX_STRING_LENGTH * 2);
- info->serial = cpu_to_le64(dma + DBC_MAX_STRING_LENGTH * 3);
- info->length = cpu_to_le32(string_length);
+ info->manufacturer = cpu_to_le64(dma + USB_MAX_STRING_DESC_LEN);
+ info->product = cpu_to_le64(dma + USB_MAX_STRING_DESC_LEN * 2);
+ info->serial = cpu_to_le64(dma + USB_MAX_STRING_DESC_LEN * 3);
+ info->length = cpu_to_le32(dbc_prepare_info_context_str_len(dbc->str_descs));
/* Populate bulk in and out endpoint contexts: */
xhci_dbc_init_ep_contexts(dbc);
@@ -525,7 +540,6 @@ static int xhci_dbc_mem_init(struct xhci_dbc *dbc, gfp_t flags)
{
int ret;
dma_addr_t deq;
- u32 string_length;
struct device *dev = dbc->dev;
/* Allocate various rings for events and transfers: */
@@ -552,11 +566,11 @@ static int xhci_dbc_mem_init(struct xhci_dbc *dbc, gfp_t flags)
goto ctx_fail;
/* Allocate the string table: */
- dbc->string_size = sizeof(*dbc->string);
- dbc->string = dma_alloc_coherent(dev, dbc->string_size,
- &dbc->string_dma, flags);
- if (!dbc->string)
- goto string_fail;
+ dbc->str_descs_size = sizeof(*dbc->str_descs);
+ dbc->str_descs = dma_alloc_coherent(dev, dbc->str_descs_size,
+ &dbc->str_descs_dma, flags);
+ if (!dbc->str_descs)
+ goto str_descs_fail;
/* Setup ERST register: */
writel(dbc->erst.num_entries, &dbc->regs->ersts);
@@ -566,16 +580,16 @@ static int xhci_dbc_mem_init(struct xhci_dbc *dbc, gfp_t flags)
dbc->ring_evt->dequeue);
lo_hi_writeq(deq, &dbc->regs->erdp);
- /* Setup strings and contexts: */
- string_length = xhci_dbc_populate_strings(dbc->string);
- xhci_dbc_init_contexts(dbc, string_length);
+ /* Setup string descriptors and contexts: */
+ xhci_dbc_populate_str_descs(dbc->str_descs, &dbc->str);
+ xhci_dbc_init_contexts(dbc);
xhci_dbc_eps_init(dbc);
dbc->state = DS_INITIALIZED;
return 0;
-string_fail:
+str_descs_fail:
dbc_free_ctx(dev, dbc->ctx);
dbc->ctx = NULL;
ctx_fail:
@@ -600,8 +614,8 @@ static void xhci_dbc_mem_cleanup(struct xhci_dbc *dbc)
xhci_dbc_eps_exit(dbc);
- dma_free_coherent(dbc->dev, dbc->string_size, dbc->string, dbc->string_dma);
- dbc->string = NULL;
+ dma_free_coherent(dbc->dev, dbc->str_descs_size, dbc->str_descs, dbc->str_descs_dma);
+ dbc->str_descs = NULL;
dbc_free_ctx(dbc->dev, dbc->ctx);
dbc->ctx = NULL;
@@ -1316,6 +1330,9 @@ xhci_alloc_dbc(struct device *dev, void __iomem *base, const struct dbc_driver *
dbc->bInterfaceProtocol = DBC_PROTOCOL;
dbc->poll_interval = DBC_POLL_INTERVAL_DEFAULT;
+ /* initialize serial, product and manufacturer with default values */
+ dbc->str = dbc_str_default;
+
if (readl(&dbc->regs->control) & DBC_CTRL_DBC_ENABLE)
goto err;
diff --git a/drivers/usb/host/xhci-dbgcap.h b/drivers/usb/host/xhci-dbgcap.h
index 5426c971d2d3..20ae4e7617f2 100644
--- a/drivers/usb/host/xhci-dbgcap.h
+++ b/drivers/usb/host/xhci-dbgcap.h
@@ -47,10 +47,6 @@ struct dbc_info_context {
#define DBC_DOOR_BELL_TARGET(p) (((p) & 0xff) << 8)
#define DBC_MAX_PACKET 1024
-#define DBC_MAX_STRING_LENGTH 64
-#define DBC_STRING_MANUFACTURER "Linux Foundation"
-#define DBC_STRING_PRODUCT "Linux USB Debug Target"
-#define DBC_STRING_SERIAL "0001"
#define DBC_CONTEXT_SIZE 64
/*
@@ -63,11 +59,31 @@ struct dbc_info_context {
#define DBC_PORTSC_LINK_CHANGE BIT(22)
#define DBC_PORTSC_CONFIG_CHANGE BIT(23)
+/*
+ * The maximum length of a string descriptor is 255, because the bLength
+ * field in the usb_string_descriptor struct is __u8. In practice the
+ * maximum length is 254, because a string descriptor consists of a 2 byte
+ * header followed by UTF-16 characters (2 bytes each). This allows for
+ * only 126 characters (code points) in the string, which is where
+ * USB_MAX_STRING_LEN comes from.
+ */
+#define USB_MAX_STRING_DESC_LEN 254
+
struct dbc_str_descs {
- char string0[DBC_MAX_STRING_LENGTH];
- char manufacturer[DBC_MAX_STRING_LENGTH];
- char product[DBC_MAX_STRING_LENGTH];
- char serial[DBC_MAX_STRING_LENGTH];
+ char string0[USB_MAX_STRING_DESC_LEN];
+ char manufacturer[USB_MAX_STRING_DESC_LEN];
+ char product[USB_MAX_STRING_DESC_LEN];
+ char serial[USB_MAX_STRING_DESC_LEN];
+};
+
+/*
+ * NULL terminated UTF-8 strings used to create UTF-16 strings
+ * (with maxiumum USB_MAX_STRING_LEN 2 byte characters).
+ */
+struct dbc_str {
+ char manufacturer[USB_MAX_STRING_LEN+1];
+ char product[USB_MAX_STRING_LEN+1];
+ char serial[USB_MAX_STRING_LEN+1];
};
#define DBC_PROTOCOL 1 /* GNU Remote Debug Command */
@@ -133,9 +149,10 @@ struct xhci_dbc {
struct xhci_erst erst;
struct xhci_container_ctx *ctx;
- struct dbc_str_descs *string;
- dma_addr_t string_dma;
- size_t string_size;
+ struct dbc_str_descs *str_descs;
+ dma_addr_t str_descs_dma;
+ size_t str_descs_size;
+ struct dbc_str str;
u16 idVendor;
u16 idProduct;
u16 bcdDevice;
--
2.43.0
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH 2/4] xhci: dbc: allow setting device serial number through sysfs
2026-01-20 18:11 [PATCH 0/4] xhci feature for usb-next Mathias Nyman
2026-01-20 18:11 ` [PATCH 1/4] xhci: dbc: prepare to expose strings through sysfs Mathias Nyman
@ 2026-01-20 18:11 ` Mathias Nyman
2026-01-20 18:11 ` [PATCH 3/4] xhci: dbc: allow setting product string " Mathias Nyman
2026-01-20 18:11 ` [PATCH 4/4] xhci: dbc: allow setting manufacturer " Mathias Nyman
3 siblings, 0 replies; 5+ messages in thread
From: Mathias Nyman @ 2026-01-20 18:11 UTC (permalink / raw)
To: gregkh; +Cc: linux-usb, Łukasz Bartosik, Mathias Nyman
From: Łukasz Bartosik <ukaszb@chromium.org>
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 <ukaszb@chromium.org>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
---
.../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 <ukaszb@chromium.org>
+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
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH 3/4] xhci: dbc: allow setting product string through sysfs
2026-01-20 18:11 [PATCH 0/4] xhci feature for usb-next Mathias Nyman
2026-01-20 18:11 ` [PATCH 1/4] xhci: dbc: prepare to expose strings through sysfs Mathias Nyman
2026-01-20 18:11 ` [PATCH 2/4] xhci: dbc: allow setting device serial number " Mathias Nyman
@ 2026-01-20 18:11 ` Mathias Nyman
2026-01-20 18:11 ` [PATCH 4/4] xhci: dbc: allow setting manufacturer " Mathias Nyman
3 siblings, 0 replies; 5+ messages in thread
From: Mathias Nyman @ 2026-01-20 18:11 UTC (permalink / raw)
To: gregkh; +Cc: linux-usb, Łukasz Bartosik, Mathias Nyman
From: Łukasz Bartosik <ukaszb@chromium.org>
Add dbc_product sysfs attribute to allow changing the product description
presented by the debug device when a host requests a string descriptor
with iProduct 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 "Linux USB Debug Target".
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 <ukaszb@chromium.org>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
---
.../testing/sysfs-bus-pci-drivers-xhci_hcd | 14 ++++++++
drivers/usb/host/xhci-dbgcap.c | 36 +++++++++++++++++++
2 files changed, 50 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-bus-pci-drivers-xhci_hcd b/Documentation/ABI/testing/sysfs-bus-pci-drivers-xhci_hcd
index b0e8ded09c16..d153162d6045 100644
--- a/Documentation/ABI/testing/sysfs-bus-pci-drivers-xhci_hcd
+++ b/Documentation/ABI/testing/sysfs-bus-pci-drivers-xhci_hcd
@@ -100,3 +100,17 @@ Description:
connected to a USB host.
The default value is "0001".
The field length can be from 1 to 126 characters.
+
+What: /sys/bus/pci/drivers/xhci_hcd/.../dbc_product
+Date: January 2026
+Contact: Łukasz Bartosik <ukaszb@chromium.org>
+Description:
+ The dbc_product attribute allows to change the product string
+ descriptor presented by the debug device when a host requests
+ a string descriptor with iProduct index.
+ Index is found in the iProduct 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 "Linux USB Debug Target".
+ 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 a78d386ffdc3..cae98576545e 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_product_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.product);
+}
+
+static ssize_t dbc_product_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.product, buf, len);
+ dbc->str.product[len] = '\0';
+
+ return size;
+}
+
static ssize_t dbc_serial_show(struct device *dev,
struct device_attribute *attr,
char *buf)
@@ -1332,6 +1366,7 @@ 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_product);
static DEVICE_ATTR_RW(dbc_bInterfaceProtocol);
static DEVICE_ATTR_RW(dbc_poll_interval_ms);
@@ -1341,6 +1376,7 @@ static struct attribute *dbc_dev_attrs[] = {
&dev_attr_dbc_idProduct.attr,
&dev_attr_dbc_bcdDevice.attr,
&dev_attr_dbc_serial.attr,
+ &dev_attr_dbc_product.attr,
&dev_attr_dbc_bInterfaceProtocol.attr,
&dev_attr_dbc_poll_interval_ms.attr,
NULL
--
2.43.0
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH 4/4] xhci: dbc: allow setting manufacturer string through sysfs
2026-01-20 18:11 [PATCH 0/4] xhci feature for usb-next Mathias Nyman
` (2 preceding siblings ...)
2026-01-20 18:11 ` [PATCH 3/4] xhci: dbc: allow setting product string " Mathias Nyman
@ 2026-01-20 18:11 ` Mathias Nyman
3 siblings, 0 replies; 5+ messages in thread
From: Mathias Nyman @ 2026-01-20 18:11 UTC (permalink / raw)
To: gregkh; +Cc: linux-usb, Łukasz Bartosik, Mathias Nyman
From: Łukasz Bartosik <ukaszb@chromium.org>
Add dbc_manufacturer sysfs attribute to allow changing the manufacturer
description presented by the debug device when a host requests a string
descriptor with iManufacturer 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 "Linux Foundation".
The string 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 <ukaszb@chromium.org>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
---
.../testing/sysfs-bus-pci-drivers-xhci_hcd | 13 +++++++
drivers/usb/host/xhci-dbgcap.c | 36 +++++++++++++++++++
2 files changed, 49 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-bus-pci-drivers-xhci_hcd b/Documentation/ABI/testing/sysfs-bus-pci-drivers-xhci_hcd
index d153162d6045..d10e6de3adb2 100644
--- a/Documentation/ABI/testing/sysfs-bus-pci-drivers-xhci_hcd
+++ b/Documentation/ABI/testing/sysfs-bus-pci-drivers-xhci_hcd
@@ -114,3 +114,16 @@ Description:
connected to a USB host.
The default value is "Linux USB Debug Target".
The field length can be from 1 to 126 characters.
+
+What: /sys/bus/pci/drivers/xhci_hcd/.../dbc_manufacturer
+Date: January 2026
+Contact: Łukasz Bartosik <ukaszb@chromium.org>
+Description:
+ The dbc_manufacturer attribute allows to change the manufacturer
+ string descriptor presented by the debug device when a host
+ requests a string descriptor with iManufacturer 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 "Linux Foundation".
+ 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 cae98576545e..9fd497e0dc7f 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_manufacturer_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.manufacturer);
+}
+
+static ssize_t dbc_manufacturer_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.manufacturer, buf, len);
+ dbc->str.manufacturer[len] = '\0';
+
+ return size;
+}
+
static ssize_t dbc_product_show(struct device *dev,
struct device_attribute *attr,
char *buf)
@@ -1367,6 +1401,7 @@ static DEVICE_ATTR_RW(dbc_idProduct);
static DEVICE_ATTR_RW(dbc_bcdDevice);
static DEVICE_ATTR_RW(dbc_serial);
static DEVICE_ATTR_RW(dbc_product);
+static DEVICE_ATTR_RW(dbc_manufacturer);
static DEVICE_ATTR_RW(dbc_bInterfaceProtocol);
static DEVICE_ATTR_RW(dbc_poll_interval_ms);
@@ -1377,6 +1412,7 @@ static struct attribute *dbc_dev_attrs[] = {
&dev_attr_dbc_bcdDevice.attr,
&dev_attr_dbc_serial.attr,
&dev_attr_dbc_product.attr,
+ &dev_attr_dbc_manufacturer.attr,
&dev_attr_dbc_bInterfaceProtocol.attr,
&dev_attr_dbc_poll_interval_ms.attr,
NULL
--
2.43.0
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