@@ -189,6 +189,16 @@ Description:
The file will read "hotplug", "wired" and "not used" if the
information is available, and "unknown" otherwise.
+What: /sys/bus/usb/devices/.../(hub interface)/portX/location
+Date: October 2018
+Contact: Bjørn Mork <bjorn@mork.no>
+Description:
+ Some platforms provide usb port physical location through
+ firmware. This is used by the kernel to pair up logical ports
+ mapping to the same physical connector. The attribute exposes the
+ raw location value as a hex integer.
+
+
What: /sys/bus/usb/devices/.../(hub interface)/portX/quirks
Date: May 2018
Contact: Nicolas Boichat <drinkcat@chromium.org>
@@ -16,6 +16,15 @@ static int usb_port_block_power_off;
static const struct attribute_group *port_dev_group[];
+static ssize_t location_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct usb_port *port_dev = to_usb_port(dev);
+
+ return sprintf(buf, "0x%08x\n", port_dev->location);
+}
+static DEVICE_ATTR_RO(location);
+
static ssize_t connect_type_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
@@ -140,6 +149,7 @@ static DEVICE_ATTR_RW(usb3_lpm_permit);
static struct attribute *port_dev_attrs[] = {
&dev_attr_connect_type.attr,
+ &dev_attr_location.attr,
&dev_attr_quirks.attr,
&dev_attr_over_current_count.attr,
NULL,
The platform firmware "location" data is used to find port peer relationships. But firmware is an unreliable source, and there are real world examples of errors leading to missing or wrong peer relationships. Debugging this is currently hard. Exporting the location attribute makes it easier to spot mismatches between the firmware data and the real world. Signed-off-by: Bjørn Mork <bjorn@mork.no> --- v4: remove unrelated ABI doc changes, thanks to Alan Stern for noticing v3: resurrect missing hunk, as pointed out by the kbuild test robot v2: Sorry, forgot to rebase the old branch before sending v1 This patch got stuck in one of my debugging branches. It proved very useful to me while trying to figure out why the "peer" link was useless on a specific host. And if it was useful to me once, then maybe it will be to someone else as well... tl;dr; The full use case for anyone interested: Some current LTE modems with USB3 SS support come with a bootloader supporting USB2 only. The application and bootloader modes are provided by different softwares running on the modem (which of course is just another Linux system with a UDC). None of the descriptors are therefore guaranteed to be identical, or even similar. Doing a firmware upgrade of such a device involves - some preparation in application mode (USB3), - rebooting into bootloader mode (USB2), and - finally booting into the upgraded application firmware (USB3) to verify the upgrade. The firmware upgrade tool should make sure it talks to the same physical device in all three phases. The only semi-reliable way to do that is to look for "new" devices in the expected mode, connected to the same physical USB port. But the locical port will change due to the USB2/3 switch, and all we are left with is the "peer" link. Which can, and do, fail due to buggy ACPI tables. This patch won't solve that problem, but it makes it a lot easier to detect. Lesson for the next time: Either submit rightaway or just delete it. Three attempts to get this even building without a warning is more than embarrassing. Sorry about that. It *is* build tested now. And even run tested. Honestly ;-) Documentation/ABI/testing/sysfs-bus-usb | 10 ++++++++++ drivers/usb/core/port.c | 10 ++++++++++ 2 files changed, 20 insertions(+)