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xhci: dbc: allow setting product string through sysfs

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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>
Link: https://patch.msgid.link/20260120181148.128712-4-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Łukasz Bartosik
2026-01-20 20:11:47 +02:00
committed by Greg Kroah-Hartman
parent 412de639b5
commit 33d15312e3
2 changed files with 50 additions and 0 deletions
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14
Documentation/ABI/testing/sysfs-bus-pci-drivers-xhci_hcd
View File

@@ -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.

36
drivers/usb/host/xhci-dbgcap.c
View File

@@ -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