Re: [PATCH v2 1/2] usb: xhci-pci: add generic auxiliary device interface
From: Jihong Min
Date: Wed May 06 2026 - 17:10:12 EST
I refactored the auxiliary device table to use PCI_DEVICE_DATA(), store the
auxiliary device name in driver_data, and use pci_match_id() inside
xhci_pci_aux_dev_name(). The relevant change is:
#define PCI_DEVICE_ID_AMD_PROM21_XHCI 0x43fd
...
static const struct pci_device_id pci_ids_have_aux[] = {
{ PCI_DEVICE_DATA(AMD, PROM21_XHCI, "hwmon") },
{ /* end: all zeroes */ }
};
...
static const char *xhci_pci_aux_dev_name(struct pci_dev *pdev)
{
const struct pci_device_id *id;
id = pci_match_id(pci_ids_have_aux, pdev);
if (!id)
return NULL;
return (const char *)id->driver_data;
}
I will include this in v3.
Thank you,
Jihong Min
On 5/7/26 05:53, Mario Limonciello wrote:
On 5/6/26 15:40, Jihong Min wrote:
[You don't often get email from hurryman2212@xxxxxxxxx. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
Some xHCI PCI controllers expose controller-specific functionality that is
not part of generic xHCI operation and is better handled by optional child
drivers in other subsystems. Add a small auxiliary device registration path
for selected xHCI PCI controllers.
The initial table creates an xhci_pci.hwmon auxiliary device for AMD
1022:43fd controllers. Store the created auxiliary device in devres so the
xhci-pci remove path destroys it before HCD teardown. Use a
PCI-domain-qualified id so auxiliary device names remain unique across PCI
domains.
This keeps xhci-pci responsible only for publishing selected controller
functions while allowing subsystem-specific drivers to bind through the
auxiliary bus.
Assisted-by: Codex:gpt-5.5
Signed-off-by: Jihong Min <hurryman2212@xxxxxxxxx>
---
drivers/usb/host/Kconfig | 10 ++++
drivers/usb/host/xhci-pci.c | 114 ++++++++++++++++++++++++++++++++++++
2 files changed, 124 insertions(+)
diff --git a/drivers/usb/host/Kconfig b/drivers/usb/host/Kconfig
index 0a277a07cf70..e0c2c7ac5c97 100644
--- a/drivers/usb/host/Kconfig
+++ b/drivers/usb/host/Kconfig
@@ -42,6 +42,16 @@ config USB_XHCI_PCI
depends on USB_PCI
default y
+config USB_XHCI_PCI_AUXDEV
+ bool "xHCI PCI auxiliary device support"
+ depends on USB_XHCI_PCI
+ select AUXILIARY_BUS
+ help
+ This enables xHCI PCI support for registering auxiliary devices
+ for selected controllers. It is used by optional child drivers
+ that bind to xHCI PCI controller-specific functionality through
+ the auxiliary bus.
+
config USB_XHCI_PCI_RENESAS
tristate "Support for additional Renesas xHCI controller with firmware"
depends on USB_XHCI_PCI
diff --git a/drivers/usb/host/xhci-pci.c b/drivers/usb/host/xhci-pci.c
index 585b2f3117b0..1ab27d2182eb 100644
--- a/drivers/usb/host/xhci-pci.c
+++ b/drivers/usb/host/xhci-pci.c
@@ -8,6 +8,8 @@
* Some code borrowed from the Linux EHCI driver.
*/
+#include <linux/auxiliary_bus.h>
+#include <linux/device/devres.h>
#include <linux/pci.h>
#include <linux/slab.h>
#include <linux/module.h>
@@ -103,6 +105,114 @@ static int xhci_pci_run(struct usb_hcd *hcd);
static int xhci_pci_update_hub_device(struct usb_hcd *hcd, struct usb_device *hdev,
struct usb_tt *tt, gfp_t mem_flags);
+#if IS_ENABLED(CONFIG_USB_XHCI_PCI_AUXDEV)
+static const struct {
+ struct pci_device_id id;
+ const char *aux_dev_name;
+} pci_ids_have_aux[] = {
+ {
+ .id = { PCI_DEVICE(PCI_VENDOR_ID_AMD, 0x43fd) }, /* PROM21 xHCI */
+ .aux_dev_name = "hwmon",
+ },
+ { /* end: all zeroes */ }
+};
+
+struct xhci_pci_aux_devres {
+ struct auxiliary_device *auxdev;
+};
+
+static bool xhci_pci_aux_match_id(const struct pci_device_id *id,
+ const struct pci_dev *pdev)
+{
+ if (id->vendor != PCI_ANY_ID && id->vendor != pdev->vendor)
+ return false;
+ if (id->device != PCI_ANY_ID && id->device != pdev->device)
+ return false;
+ if (id->subvendor != PCI_ANY_ID &&
+ id->subvendor != pdev->subsystem_vendor)
+ return false;
+ if (id->subdevice != PCI_ANY_ID &&
+ id->subdevice != pdev->subsystem_device)
+ return false;
+
+ return !((id->class ^ pdev->class) & id->class_mask);
What's wrong with pci_match_id()?
+}
+
+static const char *xhci_pci_aux_dev_name(struct pci_dev *pdev)
+{
+ int i;
+
+ for (i = 0; pci_ids_have_aux[i].aux_dev_name; i++) {
+ if (xhci_pci_aux_match_id(&pci_ids_have_aux[i].id, pdev))
+ return pci_ids_have_aux[i].aux_dev_name;
+ }
+
+ return NULL;
+}
+
+static void xhci_pci_aux_devres_release(struct device *dev, void *res)
+{
+ struct xhci_pci_aux_devres *devres = res;
+
+ if (devres->auxdev)
+ auxiliary_device_destroy(devres->auxdev);
+}
+
+static void xhci_pci_try_add_aux_device(struct pci_dev *pdev)
+{
+ struct xhci_pci_aux_devres *devres;
+ struct auxiliary_device *auxdev;
+ const char *aux_dev_name;
+
+ aux_dev_name = xhci_pci_aux_dev_name(pdev);
+ if (!aux_dev_name)
+ return;
+
+ devres = devres_alloc(xhci_pci_aux_devres_release, sizeof(*devres),
+ GFP_KERNEL);
+ if (!devres) {
+ dev_warn(&pdev->dev,
+ "failed to allocate auxiliary device state\n");
+ return;
+ }
+
+ auxdev = auxiliary_device_create(&pdev->dev, KBUILD_MODNAME,
+ aux_dev_name, NULL,
+ (pci_domain_nr(pdev->bus) << 16) |
+ pci_dev_id(pdev));
+ if (!auxdev) {
+ devres_free(devres);
+ dev_warn(&pdev->dev, "failed to add %s auxiliary device\n",
+ aux_dev_name);
+ return;
+ }
+
+ devres->auxdev = auxdev;
+ devres_add(&pdev->dev, devres);
+}
+
+static void xhci_pci_try_remove_aux_device(struct pci_dev *pdev)
+{
+ struct xhci_pci_aux_devres *devres;
+
+ devres = devres_find(&pdev->dev, xhci_pci_aux_devres_release, NULL,
+ NULL);
+ if (!devres || !devres->auxdev)
+ return;
+
+ auxiliary_device_destroy(devres->auxdev);
+ devres->auxdev = NULL;
+}
+#else
+static inline void xhci_pci_try_add_aux_device(struct pci_dev *pdev)
+{
+}
+
+static inline void xhci_pci_try_remove_aux_device(struct pci_dev *pdev)
+{
+}
+#endif
+
static const struct xhci_driver_overrides xhci_pci_overrides __initconst = {
.reset = xhci_pci_setup,
.start = xhci_pci_run,
@@ -677,6 +787,8 @@ int xhci_pci_common_probe(struct pci_dev *dev, const struct pci_device_id *id)
if (device_property_read_bool(&dev->dev, "ti,pwron-active-high"))
pci_clear_and_set_config_dword(dev, 0xE0, 0, 1 << 22);
+ xhci_pci_try_add_aux_device(dev);
+
return 0;
put_usb3_hcd:
@@ -713,6 +825,8 @@ void xhci_pci_remove(struct pci_dev *dev)
xhci = hcd_to_xhci(pci_get_drvdata(dev));
set_power_d3 = xhci->quirks & XHCI_SPURIOUS_WAKEUP;
+ xhci_pci_try_remove_aux_device(dev);
+
xhci->xhc_state |= XHCI_STATE_REMOVING;
if (pci_choose_state(dev, PMSG_SUSPEND) == PCI_D0)
--
2.53.0