[PATCH v2 0/6] USB: add usb_make_subpath() to replace strlcat() in input drivers

[PATCH v2 0/6] USB: add usb_make_subpath() to replace strlcat() in input drivers

[Shihuang Liu]

Several USB input drivers build their physical device paths by calling
usb_make_path() and then appending "/input0" or "/input1" with strlcat().

In preparation for removing the deprecated strlcat() API [1], introduce
usb_make_subpath() and convert these callers to use it.

Patch 1 adds the helper in include/linux/usb.h. Patches 2-6 convert the
joystick, misc, mouse, tablet and touchscreen drivers, respectively.

Link: https://github.com/KSPP/linux/issues/370 [1]
Signed-off-by: Shihuang Liu <shlomojune6@gmail.com>

---

Changes in v2:
  - Add usb_make_subpath() as the first patch in the series.
  - Use the helper instead of open-coding strnlen() and strscpy() in
    each input driver.
  - Link to v1: https://lore.kernel.org/all/20261016170411.51025-1-shlomojune6@gmail.com/

---

Shihuang Liu (6):
  USB: add usb_make_subpath() for formatted device subpaths
  Input: joystick - use usb_make_subpath()
  Input: misc - use usb_make_subpath()
  Input: mouse - use usb_make_subpath()
  Input: tablet - use usb_make_subpath()
  Input: touchscreen - use usb_make_subpath()

 drivers/input/joystick/pxrc.c              |  3 +--
 drivers/input/joystick/xpad.c              |  3 +--
 drivers/input/misc/ati_remote2.c           |  3 +--
 drivers/input/misc/cm109.c                 |  3 +--
 drivers/input/misc/ims-pcu.c               |  6 ++---
 drivers/input/misc/keyspan_remote.c        |  3 +--
 drivers/input/misc/powermate.c             |  3 +--
 drivers/input/misc/yealink.c               |  3 +--
 drivers/input/mouse/appletouch.c           |  3 +--
 drivers/input/mouse/bcm5974.c              |  3 +--
 drivers/input/mouse/synaptics_usb.c        |  3 +--
 drivers/input/tablet/acecad.c              |  3 +--
 drivers/input/tablet/aiptek.c              |  6 ++---
 drivers/input/tablet/hanwang.c             |  3 +--
 drivers/input/tablet/kbtab.c               |  3 +--
 drivers/input/tablet/pegasus_notetaker.c   |  3 +--
 drivers/input/touchscreen/sur40.c          |  3 +--
 drivers/input/touchscreen/usbtouchscreen.c |  3 +--
 include/linux/usb.h                        | 29 ++++++++++++++++++++++
 19 files changed, 49 insertions(+), 40 deletions(-)

-- 
2.43.0

[PATCH v2 1/6] USB: add usb_make_subpath() for formatted device subpaths

[Shihuang Liu]

USB drivers often build device paths by calling usb_make_path() :and
then appending a subpath. Several callers use the deprecated strlcat()
API for this.

In preparation for removing the deprecated strlcat() API[1], add
usb_make_subpath() to format the USB device path.

Link: https://github.com/KSPP/linux/issues/370 [1]
Signed-off-by: Shihuang Liu <shlomojune6@gmail.com>
---
 include/linux/usb.h | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/include/linux/usb.h b/include/linux/usb.h
index 1da4ad1610bca..c90ccea0cdbf6 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -14,6 +14,7 @@
 #include <linux/errno.h>        /* for -ENODEV */
 #include <linux/delay.h>	/* for mdelay() */
 #include <linux/interrupt.h>	/* for in_interrupt() */
+#include <linux/stdarg.h>	/* for va_list */
 #include <linux/list.h>		/* for struct list_head */
 #include <linux/kref.h>		/* for struct kref */
 #include <linux/device.h>	/* for struct device */
@@ -987,6 +988,34 @@ static inline int usb_make_path(struct usb_device *dev, char *buf, size_t size)
 	return (actual >= (int)size) ? -1 : actual;
 }
 
+/**
+ * usb_make_subpath - returns a stable device path and formatted subpath
+ * @dev: the device whose path is being constructed
+ * @buf: where to put the string
+ * @size: how big is "buf"?
+ * @fmt: format string for the subpath, without the leading slash
+ * @...: arguments for @fmt
+ *
+ * Return: Length of the string (> 0) or negative if size was too small.
+ */
+static inline __printf(4, 5)
+int usb_make_subpath(struct usb_device *dev, char *buf, size_t size,
+		     const char *fmt, ...)
+{
+	struct va_format vaf;
+	va_list args;
+	int actual;
+
+	va_start(args, fmt);
+	vaf.fmt = fmt;
+	vaf.va = &args;
+	actual = snprintf(buf, size, "usb-%s-%s/%pV", dev->bus->bus_name,
+			  dev->devpath, &vaf);
+	va_end(args);
+
+	return (actual >= (int)size) ? -1 : actual;
+}
+
 /*-------------------------------------------------------------------------*/
 
 #define USB_DEVICE_ID_MATCH_DEVICE \
-- 
2.43.0

[PATCH v2 2/6] Input: joystick - use usb_make_subpath()

[Shihuang Liu]

The pxrc and xpad drivers build their input device physical paths
by appending "/input0" with strlcat() after usb_make_path().

In preparation for removing the deprecated strlcat() API [1],
replace each pair of calls with usb_make_subpath(). The helper
formats the USB path and the "input0" subpath in one call,
avoiding a separate buffer scan and append operation.

Link: https://github.com/KSPP/linux/issues/370 [1]
Signed-off-by: Shihuang Liu <shlomojune6@gmail.com>
---
 drivers/input/joystick/pxrc.c | 3 +--
 drivers/input/joystick/xpad.c | 3 +--
 2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/input/joystick/pxrc.c b/drivers/input/joystick/pxrc.c
index 52d9eab667b7a..1a11e73d7cd04 100644
--- a/drivers/input/joystick/pxrc.c
+++ b/drivers/input/joystick/pxrc.c
@@ -169,8 +169,7 @@ static int pxrc_probe(struct usb_interface *intf,
 
 	pxrc->input->name = "PXRC Flight Controller Adapter";
 
-	usb_make_path(udev, pxrc->phys, sizeof(pxrc->phys));
-	strlcat(pxrc->phys, "/input0", sizeof(pxrc->phys));
+	usb_make_subpath(udev, pxrc->phys, sizeof(pxrc->phys), "input0");
 	pxrc->input->phys = pxrc->phys;
 
 	usb_to_input_id(udev, &pxrc->input->id);
diff --git a/drivers/input/joystick/xpad.c b/drivers/input/joystick/xpad.c
index feb8f368f834e..0f7ca5adaeee7 100644
--- a/drivers/input/joystick/xpad.c
+++ b/drivers/input/joystick/xpad.c
@@ -2059,8 +2059,7 @@ static int xpad_probe(struct usb_interface *intf, const struct usb_device_id *id
 	if (!xpad)
 		return -ENOMEM;
 
-	usb_make_path(udev, xpad->phys, sizeof(xpad->phys));
-	strlcat(xpad->phys, "/input0", sizeof(xpad->phys));
+	usb_make_subpath(udev, xpad->phys, sizeof(xpad->phys), "input0");
 
 	xpad->idata = usb_alloc_coherent(udev, XPAD_PKT_LEN,
 					 GFP_KERNEL, &xpad->idata_dma);
-- 
2.43.0

[PATCH v2 3/6] Input: misc - use usb_make_subpath()

[Shihuang Liu]

The ati_remote2, cm109, ims-pcu, keyspan_remote, powermate and yealink
drivers build their input device physical paths by appending a subpath
with strlcat() after usb_make_path(). Most use "/input0"; ims-pcu also
uses "/input1" for its gamepad interface.

In preparation for removing the deprecated strlcat() API [1], replace
these pairs of calls with usb_make_subpath(). Pass "input0" or "input1"
as appropriate so the helper constructs each physical path in one call,
avoiding a separate buffer scan and append operation.

Link: https://github.com/KSPP/linux/issues/370 [1]

Signed-off-by: Shihuang Liu <shlomojune6@gmail.com>
---
 drivers/input/misc/ati_remote2.c    | 3 +--
 drivers/input/misc/cm109.c          | 3 +--
 drivers/input/misc/ims-pcu.c        | 6 ++----
 drivers/input/misc/keyspan_remote.c | 3 +--
 drivers/input/misc/powermate.c      | 3 +--
 drivers/input/misc/yealink.c        | 3 +--
 6 files changed, 7 insertions(+), 14 deletions(-)

diff --git a/drivers/input/misc/ati_remote2.c b/drivers/input/misc/ati_remote2.c
index 8db2dca84975c..20cb7b8efcc0b 100644
--- a/drivers/input/misc/ati_remote2.c
+++ b/drivers/input/misc/ati_remote2.c
@@ -822,8 +822,7 @@ static int ati_remote2_probe(struct usb_interface *interface, const struct usb_d
 	if (r)
 		goto fail3;
 
-	usb_make_path(udev, ar2->phys, sizeof(ar2->phys));
-	strlcat(ar2->phys, "/input0", sizeof(ar2->phys));
+	usb_make_subpath(udev, ar2->phys, sizeof(ar2->phys), "input0");
 
 	strlcat(ar2->name, "ATI Remote Wonder II", sizeof(ar2->name));
 
diff --git a/drivers/input/misc/cm109.c b/drivers/input/misc/cm109.c
index 353d3c1d347d5..06d8f0dab4b37 100644
--- a/drivers/input/misc/cm109.c
+++ b/drivers/input/misc/cm109.c
@@ -765,8 +765,7 @@ static int cm109_usb_probe(struct usb_interface *intf,
 	dev->urb_ctl->dev = udev;
 
 	/* find out the physical bus location */
-	usb_make_path(udev, dev->phys, sizeof(dev->phys));
-	strlcat(dev->phys, "/input0", sizeof(dev->phys));
+	usb_make_subpath(udev, dev->phys, sizeof(dev->phys), "input0");
 
 	/* register settings for the input device */
 	input_dev->name = nfo->name;
diff --git a/drivers/input/misc/ims-pcu.c b/drivers/input/misc/ims-pcu.c
index b1a0edcc49b4e..e629a327fdd76 100644
--- a/drivers/input/misc/ims-pcu.c
+++ b/drivers/input/misc/ims-pcu.c
@@ -215,8 +215,7 @@ static int ims_pcu_setup_buttons(struct ims_pcu *pcu,
 	snprintf(buttons->name, sizeof(buttons->name),
 		 "IMS PCU#%d Button Interface", pcu->device_no);
 
-	usb_make_path(pcu->udev, buttons->phys, sizeof(buttons->phys));
-	strlcat(buttons->phys, "/input0", sizeof(buttons->phys));
+	usb_make_subpath(pcu->udev, buttons->phys, sizeof(buttons->phys), "input0");
 
 	memcpy(buttons->keymap, keymap, sizeof(*keymap) * keymap_len);
 
@@ -301,8 +300,7 @@ static int ims_pcu_setup_gamepad(struct ims_pcu *pcu)
 	snprintf(gamepad->name, sizeof(gamepad->name),
 		 "IMS PCU#%d Gamepad Interface", pcu->device_no);
 
-	usb_make_path(pcu->udev, gamepad->phys, sizeof(gamepad->phys));
-	strlcat(gamepad->phys, "/input1", sizeof(gamepad->phys));
+	usb_make_subpath(pcu->udev, gamepad->phys, sizeof(gamepad->phys), "input1");
 
 	input->name = gamepad->name;
 	input->phys = gamepad->phys;
diff --git a/drivers/input/misc/keyspan_remote.c b/drivers/input/misc/keyspan_remote.c
index 70cd6586459ef..68c969657806d 100644
--- a/drivers/input/misc/keyspan_remote.c
+++ b/drivers/input/misc/keyspan_remote.c
@@ -481,8 +481,7 @@ static int keyspan_probe(struct usb_interface *interface, const struct usb_devic
 			 le16_to_cpu(udev->descriptor.idVendor),
 			 le16_to_cpu(udev->descriptor.idProduct));
 
-	usb_make_path(udev, remote->phys, sizeof(remote->phys));
-	strlcat(remote->phys, "/input0", sizeof(remote->phys));
+	usb_make_subpath(udev, remote->phys, sizeof(remote->phys), "input0");
 	memcpy(remote->keymap, keyspan_key_table, sizeof(remote->keymap));
 
 	input_dev->name = remote->name;
diff --git a/drivers/input/misc/powermate.c b/drivers/input/misc/powermate.c
index 754379d2625cf..f004cfca795ec 100644
--- a/drivers/input/misc/powermate.c
+++ b/drivers/input/misc/powermate.c
@@ -333,8 +333,7 @@ static int powermate_probe(struct usb_interface *intf, const struct usb_device_i
 	pm->intf = intf;
 	pm->input = input_dev;
 
-	usb_make_path(udev, pm->phys, sizeof(pm->phys));
-	strlcat(pm->phys, "/input0", sizeof(pm->phys));
+	usb_make_subpath(udev, pm->phys, sizeof(pm->phys), "input0");
 
 	spin_lock_init(&pm->lock);
 
diff --git a/drivers/input/misc/yealink.c b/drivers/input/misc/yealink.c
index 560f895a00cda..9a8ee7a586f44 100644
--- a/drivers/input/misc/yealink.c
+++ b/drivers/input/misc/yealink.c
@@ -890,8 +890,7 @@ static int usb_probe(struct usb_interface *intf, const struct usb_device_id *id)
 	yld->urb_ctl->dev = udev;
 
 	/* find out the physical bus location */
-	usb_make_path(udev, yld->phys, sizeof(yld->phys));
-	strlcat(yld->phys,  "/input0", sizeof(yld->phys));
+	usb_make_subpath(udev, yld->phys, sizeof(yld->phys), "input0");
 
 	/* register settings for the input device */
 	input_dev->name = nfo->name;
-- 
2.43.0

[PATCH v2 4/6] Input: mouse - use usb_make_subpath()

[Shihuang Liu]

The appletouch, bcm5974 and synaptics_usb drivers build their input
device physical paths by appending "/input0" with strlcat() after
usb_make_path().

In preparation for removing the deprecated strlcat() API [1],
replace each pair of calls with usb_make_subpath(). The
helper formats the USB path and the "input0" subpath in
one call, avoiding a separate buffer scan and append operation.

Link: https://github.com/KSPP/linux/issues/370 [1]
Signed-off-by: Shihuang Liu <shlomojune6@gmail.com>
---
 drivers/input/mouse/appletouch.c    | 3 +--
 drivers/input/mouse/bcm5974.c       | 3 +--
 drivers/input/mouse/synaptics_usb.c | 3 +--
 3 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/input/mouse/appletouch.c b/drivers/input/mouse/appletouch.c
index eebeb57515e1c..b536dfae427de 100644
--- a/drivers/input/mouse/appletouch.c
+++ b/drivers/input/mouse/appletouch.c
@@ -874,8 +874,7 @@ static int atp_probe(struct usb_interface *iface,
 	if (error)
 		goto err_free_buffer;
 
-	usb_make_path(udev, dev->phys, sizeof(dev->phys));
-	strlcat(dev->phys, "/input0", sizeof(dev->phys));
+	usb_make_subpath(udev, dev->phys, sizeof(dev->phys), "input0");
 
 	input_dev->name = "appletouch";
 	input_dev->phys = dev->phys;
diff --git a/drivers/input/mouse/bcm5974.c b/drivers/input/mouse/bcm5974.c
index e772bac3b64c0..0732bf3a97adc 100644
--- a/drivers/input/mouse/bcm5974.c
+++ b/drivers/input/mouse/bcm5974.c
@@ -989,8 +989,7 @@ static int bcm5974_probe(struct usb_interface *iface,
 	dev->tp_urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
 
 	/* create bcm5974 device */
-	usb_make_path(udev, dev->phys, sizeof(dev->phys));
-	strlcat(dev->phys, "/input0", sizeof(dev->phys));
+	usb_make_subpath(udev, dev->phys, sizeof(dev->phys), "input0");
 
 	input_dev->name = "bcm5974";
 	input_dev->phys = dev->phys;
diff --git a/drivers/input/mouse/synaptics_usb.c b/drivers/input/mouse/synaptics_usb.c
index 880a0c79148cd..7da22118ce576 100644
--- a/drivers/input/mouse/synaptics_usb.c
+++ b/drivers/input/mouse/synaptics_usb.c
@@ -353,8 +353,7 @@ static int synusb_probe(struct usb_interface *intf,
 	if (synusb->flags & SYNUSB_STICK)
 		strlcat(synusb->name, " (Stick)", sizeof(synusb->name));
 
-	usb_make_path(udev, synusb->phys, sizeof(synusb->phys));
-	strlcat(synusb->phys, "/input0", sizeof(synusb->phys));
+	usb_make_subpath(udev, synusb->phys, sizeof(synusb->phys), "input0");
 
 	input_dev->name = synusb->name;
 	input_dev->phys = synusb->phys;
-- 
2.43.0

[PATCH v2 5/6] Input: tablet - use usb_make_subpath()

[Shihuang Liu]

The acecad, aiptek, hanwang, kbtab and pegasus_notetaker drivers build
their input device physical paths by appending "/input0" with strlcat()
after usb_make_path().

In preparation for removing the deprecated strlcat() API [1], replace
each pair of calls with usb_make_subpath(). The helper formats the USB
path and the "input0" subpath in one call, avoiding a separate buffer
scan and append operation.

Link: https://github.com/KSPP/linux/issues/370 [1]
Signed-off-by: Shihuang Liu <shlomojune6@gmail.com>
---
 drivers/input/tablet/acecad.c            | 3 +--
 drivers/input/tablet/aiptek.c            | 6 ++----
 drivers/input/tablet/hanwang.c           | 3 +--
 drivers/input/tablet/kbtab.c             | 3 +--
 drivers/input/tablet/pegasus_notetaker.c | 3 +--
 5 files changed, 6 insertions(+), 12 deletions(-)

diff --git a/drivers/input/tablet/acecad.c b/drivers/input/tablet/acecad.c
index ba79dff21aac8..c12b0a0181837 100644
--- a/drivers/input/tablet/acecad.c
+++ b/drivers/input/tablet/acecad.c
@@ -160,8 +160,7 @@ static int usb_acecad_probe(struct usb_interface *intf, const struct usb_device_
 		strlcat(acecad->name, dev->product, sizeof(acecad->name));
 	}
 
-	usb_make_path(dev, acecad->phys, sizeof(acecad->phys));
-	strlcat(acecad->phys, "/input0", sizeof(acecad->phys));
+	usb_make_subpath(dev, acecad->phys, sizeof(acecad->phys), "input0");
 
 	input_dev->name = acecad->name;
 	input_dev->phys = acecad->phys;
diff --git a/drivers/input/tablet/aiptek.c b/drivers/input/tablet/aiptek.c
index 0c1acb9e6b437..cc68ee82c12c3 100644
--- a/drivers/input/tablet/aiptek.c
+++ b/drivers/input/tablet/aiptek.c
@@ -1705,10 +1705,8 @@ aiptek_probe(struct usb_interface *intf, const struct usb_device_id *id)
 	 * & a tablet, and the inputX number actually will tell
 	 * us something...
 	 */
-	usb_make_path(usbdev, aiptek->features.usbPath,
-			sizeof(aiptek->features.usbPath));
-	strlcat(aiptek->features.usbPath, "/input0",
-		sizeof(aiptek->features.usbPath));
+	usb_make_subpath(usbdev, aiptek->features.usbPath,
+			sizeof(aiptek->features.usbPath), "input0");
 
 	/* Set up client data, pointers to open and close routines
 	 * for the input device.
diff --git a/drivers/input/tablet/hanwang.c b/drivers/input/tablet/hanwang.c
index fd5a7e761dcc4..a9521bbc89646 100644
--- a/drivers/input/tablet/hanwang.c
+++ b/drivers/input/tablet/hanwang.c
@@ -350,8 +350,7 @@ static int hanwang_probe(struct usb_interface *intf, const struct usb_device_id
 	hanwang->usbdev = dev;
 	hanwang->dev = input_dev;
 
-	usb_make_path(dev, hanwang->phys, sizeof(hanwang->phys));
-	strlcat(hanwang->phys, "/input0", sizeof(hanwang->phys));
+	usb_make_subpath(dev, hanwang->phys, sizeof(hanwang->phys), "input0");
 
 	strscpy(hanwang->name, hanwang->features->name, sizeof(hanwang->name));
 	input_dev->name = hanwang->name;
diff --git a/drivers/input/tablet/kbtab.c b/drivers/input/tablet/kbtab.c
index 6ce70c8e2d7cc..f777118ed7c8f 100644
--- a/drivers/input/tablet/kbtab.c
+++ b/drivers/input/tablet/kbtab.c
@@ -137,8 +137,7 @@ static int kbtab_probe(struct usb_interface *intf, const struct usb_device_id *i
 	kbtab->intf = intf;
 	kbtab->dev = input_dev;
 
-	usb_make_path(dev, kbtab->phys, sizeof(kbtab->phys));
-	strlcat(kbtab->phys, "/input0", sizeof(kbtab->phys));
+	usb_make_subpath(dev, kbtab->phys, sizeof(kbtab->phys), "input0");
 
 	input_dev->name = "KB Gear Tablet";
 	input_dev->phys = kbtab->phys;
diff --git a/drivers/input/tablet/pegasus_notetaker.c b/drivers/input/tablet/pegasus_notetaker.c
index 85390ae423076..28fbae98f7399 100644
--- a/drivers/input/tablet/pegasus_notetaker.c
+++ b/drivers/input/tablet/pegasus_notetaker.c
@@ -354,8 +354,7 @@ static int pegasus_probe(struct usb_interface *intf,
 			 le16_to_cpu(dev->descriptor.idVendor),
 			 le16_to_cpu(dev->descriptor.idProduct));
 
-	usb_make_path(dev, pegasus->phys, sizeof(pegasus->phys));
-	strlcat(pegasus->phys, "/input0", sizeof(pegasus->phys));
+	usb_make_subpath(dev, pegasus->phys, sizeof(pegasus->phys), "input0");
 
 	INIT_WORK(&pegasus->init, pegasus_init);
 
-- 
2.43.0

[PATCH v2 6/6] Input: touchscreen - use usb_make_subpath()

[Shihuang Liu]

The sur40 and usbtouchscreen drivers build their input device physical
paths by appending "/input0" with strlcat() after usb_make_path().

In preparation for removing the deprecated strlcat() API [1], replace
each pair of calls with usb_make_subpath(). The helper formats the
USB path and the "input0" subpath in one call, avoiding a separate
buffer scan and append operation.

Link: https://github.com/KSPP/linux/issues/370 [1]
Signed-off-by: Shihuang Liu <shlomojune6@gmail.com>
---
 drivers/input/touchscreen/sur40.c          | 3 +--
 drivers/input/touchscreen/usbtouchscreen.c | 3 +--
 2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/input/touchscreen/sur40.c b/drivers/input/touchscreen/sur40.c
index 77ec2c94b91fd..7702eead123e2 100644
--- a/drivers/input/touchscreen/sur40.c
+++ b/drivers/input/touchscreen/sur40.c
@@ -690,8 +690,7 @@ static int sur40_probe(struct usb_interface *interface,
 	/* Set up regular input device structure */
 	input->name = DRIVER_LONG;
 	usb_to_input_id(usbdev, &input->id);
-	usb_make_path(usbdev, sur40->phys, sizeof(sur40->phys));
-	strlcat(sur40->phys, "/input0", sizeof(sur40->phys));
+	usb_make_subpath(usbdev, sur40->phys, sizeof(sur40->phys), "input0");
 	input->phys = sur40->phys;
 	input->dev.parent = &interface->dev;
 
diff --git a/drivers/input/touchscreen/usbtouchscreen.c b/drivers/input/touchscreen/usbtouchscreen.c
index 0bbacb517c286..fd2b896675dee 100644
--- a/drivers/input/touchscreen/usbtouchscreen.c
+++ b/drivers/input/touchscreen/usbtouchscreen.c
@@ -1512,8 +1512,7 @@ static int usbtouch_probe(struct usb_interface *intf,
 			 le16_to_cpu(udev->descriptor.idVendor),
 			 le16_to_cpu(udev->descriptor.idProduct));
 
-	usb_make_path(udev, usbtouch->phys, sizeof(usbtouch->phys));
-	strlcat(usbtouch->phys, "/input0", sizeof(usbtouch->phys));
+	usb_make_subpath(udev, usbtouch->phys, sizeof(usbtouch->phys), "input0");
 
 	input_dev->name = usbtouch->name;
 	input_dev->phys = usbtouch->phys;
-- 
2.43.0

Re: [PATCH v2 1/6] USB: add usb_make_subpath() for formatted device subpaths

[Alejandro Colomar]

[-- Attachment #1: Type: text/plain, Size: 2490 bytes --]

Hi Shihuang,

> Date: 2026-10-21 20:31:41+0800
> From: Shihuang Liu <shlomojune6@gmail.com>
>
> USB drivers often build device paths by calling usb_make_path() :and
> then appending a subpath. Several callers use the deprecated strlcat()
> API for this.
> 
> In preparation for removing the deprecated strlcat() API[1], add
> usb_make_subpath() to format the USB device path.
> 
> Link: https://github.com/KSPP/linux/issues/370 [1]
> Signed-off-by: Shihuang Liu <shlomojune6@gmail.com>
> ---
>  include/linux/usb.h | 29 +++++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff --git a/include/linux/usb.h b/include/linux/usb.h
> index 1da4ad1610bca..c90ccea0cdbf6 100644
> --- a/include/linux/usb.h
> +++ b/include/linux/usb.h
> @@ -14,6 +14,7 @@
>  #include <linux/errno.h>        /* for -ENODEV */
>  #include <linux/delay.h>	/* for mdelay() */
>  #include <linux/interrupt.h>	/* for in_interrupt() */
> +#include <linux/stdarg.h>	/* for va_list */
>  #include <linux/list.h>		/* for struct list_head */
>  #include <linux/kref.h>		/* for struct kref */
>  #include <linux/device.h>	/* for struct device */
> @@ -987,6 +988,34 @@ static inline int usb_make_path(struct usb_device *dev, char *buf, size_t size)
>  	return (actual >= (int)size) ? -1 : actual;
>  }
>  
> +/**
> + * usb_make_subpath - returns a stable device path and formatted subpath
> + * @dev: the device whose path is being constructed
> + * @buf: where to put the string
> + * @size: how big is "buf"?
> + * @fmt: format string for the subpath, without the leading slash
> + * @...: arguments for @fmt
> + *
> + * Return: Length of the string (> 0) or negative if size was too small.
> + */
> +static inline __printf(4, 5)
> +int usb_make_subpath(struct usb_device *dev, char *buf, size_t size,
> +		     const char *fmt, ...)
> +{
> +	struct va_format vaf;
> +	va_list args;
> +	int actual;
> +
> +	va_start(args, fmt);
> +	vaf.fmt = fmt;
> +	vaf.va = &args;
> +	actual = snprintf(buf, size, "usb-%s-%s/%pV", dev->bus->bus_name,
> +			  dev->devpath, &vaf);
> +	va_end(args);
> +
> +	return (actual >= (int)size) ? -1 : actual;

Why are you open-coding usb_make_path() here instead of calling it?


Have a lovely day!
Alex

> +}
> +
>  /*-------------------------------------------------------------------------*/
>  
>  #define USB_DEVICE_ID_MATCH_DEVICE \
> -- 
> 2.43.0
> 
> 

-- 
<https://www.alejandro-colomar.es>

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Re: [PATCH v2 2/6] Input: joystick - use usb_make_subpath()

[Alejandro Colomar]

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Hi Shihuang,

> Date: 2026-10-21 20:31:42+0800
> From: Shihuang Liu <shlomojune6@gmail.com>
>
> The pxrc and xpad drivers build their input device physical paths
> by appending "/input0" with strlcat() after usb_make_path().
> 
> In preparation for removing the deprecated strlcat() API [1],
> replace each pair of calls with usb_make_subpath(). The helper
> formats the USB path and the "input0" subpath in one call,
> avoiding a separate buffer scan and append operation.
> 
> Link: https://github.com/KSPP/linux/issues/370 [1]
> Signed-off-by: Shihuang Liu <shlomojune6@gmail.com>
> ---
>  drivers/input/joystick/pxrc.c | 3 +--
>  drivers/input/joystick/xpad.c | 3 +--
>  2 files changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/input/joystick/pxrc.c b/drivers/input/joystick/pxrc.c
> index 52d9eab667b7a..1a11e73d7cd04 100644
> --- a/drivers/input/joystick/pxrc.c
> +++ b/drivers/input/joystick/pxrc.c
> @@ -169,8 +169,7 @@ static int pxrc_probe(struct usb_interface *intf,
>  
>  	pxrc->input->name = "PXRC Flight Controller Adapter";
>  
> -	usb_make_path(udev, pxrc->phys, sizeof(pxrc->phys));
> -	strlcat(pxrc->phys, "/input0", sizeof(pxrc->phys));
> +	usb_make_subpath(udev, pxrc->phys, sizeof(pxrc->phys), "input0");

To be honest, I think the composed approach is more readable.  You don't
need to learn a new _subpath function with all the details it has.

Everyone knows what a str*cat() (or str*cpy, FWIW) function does.

I'd rather improve this by adding strscat().  The reason for removing
strlcat(3) is that it is vulnerable to DoS, and that it is inefficient,
but it is good at producing readable code, and a replacement should not
degrade that.


Have a lovely day!
Alex

>  	pxrc->input->phys = pxrc->phys;
>  
>  	usb_to_input_id(udev, &pxrc->input->id);
> diff --git a/drivers/input/joystick/xpad.c b/drivers/input/joystick/xpad.c
> index feb8f368f834e..0f7ca5adaeee7 100644
> --- a/drivers/input/joystick/xpad.c
> +++ b/drivers/input/joystick/xpad.c
> @@ -2059,8 +2059,7 @@ static int xpad_probe(struct usb_interface *intf, const struct usb_device_id *id
>  	if (!xpad)
>  		return -ENOMEM;
>  
> -	usb_make_path(udev, xpad->phys, sizeof(xpad->phys));
> -	strlcat(xpad->phys, "/input0", sizeof(xpad->phys));
> +	usb_make_subpath(udev, xpad->phys, sizeof(xpad->phys), "input0");
>  
>  	xpad->idata = usb_alloc_coherent(udev, XPAD_PKT_LEN,
>  					 GFP_KERNEL, &xpad->idata_dma);
> -- 
> 2.43.0
> 
> 

-- 
<https://www.alejandro-colomar.es>

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Re: [PATCH v2 1/6] USB: add usb_make_subpath() for formatted device subpaths

[Greg KH]

On Wed, Oct 21, 2026 at 08:31:41PM +0800, Shihuang Liu wrote:
> USB drivers often build device paths by calling usb_make_path() :and
> then appending a subpath. Several callers use the deprecated strlcat()
> API for this.
> 
> In preparation for removing the deprecated strlcat() API[1], add
> usb_make_subpath() to format the USB device path.
> 
> Link: https://github.com/KSPP/linux/issues/370 [1]
> Signed-off-by: Shihuang Liu <shlomojune6@gmail.com>
> ---
>  include/linux/usb.h | 29 +++++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)

Did you forget to use get_maintainer.pl for this?

Re: [PATCH v2 2/6] Input: joystick - use usb_make_subpath()

[Dmitry Torokhov]

On Wed, Oct 21, 2026 at 03:21:28PM +0200, Alejandro Colomar wrote:
> Hi Shihuang,
> 
> > Date: 2026-10-21 20:31:42+0800
> > From: Shihuang Liu <shlomojune6@gmail.com>
> >
> > The pxrc and xpad drivers build their input device physical paths
> > by appending "/input0" with strlcat() after usb_make_path().
> > 
> > In preparation for removing the deprecated strlcat() API [1],
> > replace each pair of calls with usb_make_subpath(). The helper
> > formats the USB path and the "input0" subpath in one call,
> > avoiding a separate buffer scan and append operation.
> > 
> > Link: https://github.com/KSPP/linux/issues/370 [1]
> > Signed-off-by: Shihuang Liu <shlomojune6@gmail.com>
> > ---
> >  drivers/input/joystick/pxrc.c | 3 +--
> >  drivers/input/joystick/xpad.c | 3 +--
> >  2 files changed, 2 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/input/joystick/pxrc.c b/drivers/input/joystick/pxrc.c
> > index 52d9eab667b7a..1a11e73d7cd04 100644
> > --- a/drivers/input/joystick/pxrc.c
> > +++ b/drivers/input/joystick/pxrc.c
> > @@ -169,8 +169,7 @@ static int pxrc_probe(struct usb_interface *intf,
> >  
> >  	pxrc->input->name = "PXRC Flight Controller Adapter";
> >  
> > -	usb_make_path(udev, pxrc->phys, sizeof(pxrc->phys));
> > -	strlcat(pxrc->phys, "/input0", sizeof(pxrc->phys));
> > +	usb_make_subpath(udev, pxrc->phys, sizeof(pxrc->phys), "input0");
> 
> To be honest, I think the composed approach is more readable.  You don't
> need to learn a new _subpath function with all the details it has.
> 
> Everyone knows what a str*cat() (or str*cpy, FWIW) function does.
> 
> I'd rather improve this by adding strscat().  The reason for removing
> strlcat(3) is that it is vulnerable to DoS, and that it is inefficient,
> but it is good at producing readable code, and a replacement should not
> degrade that.

Well, there is absolutely no performance concerns in this code, so
another option is to simply leave it as is. I see no benefit here from
using yet another variant of str*cat().

Thanks.

-- 
Dmitry