Add debug support for experimenting with USB timing delay
values on the fly. This provides a debug interface through
/sys/kernel/usb where a user can tweak the values. The code
enforces the spec minimums so that a user can't set them
too low.
Signed-off-by: Todd Brandt <todd.e.brandt@xxxxxxxxxxxxxxx>
---
drivers/usb/core/hub.c | 100 +++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 100 insertions(+)
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 43242e3..6dea6a7 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -5265,8 +5265,98 @@ static struct usb_driver hub_driver = {
.supports_autosuspend = 1,
};
+static ssize_t tdrsmdn_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%d\n", usb_timing.tdrsmdn);
+}
+
+static ssize_t tdrsmdn_store(struct kobject *kobj,
+ struct kobj_attribute *attr, const char *buf, size_t count)
+{
+ int ret, val;
+
+ ret = kstrtoint(buf, 10, &val);
+ if (ret < 0)
+ return ret;
+
+ if (val < 20)
+ usb_timing.tdrsmdn = 20;
+ else
+ usb_timing.tdrsmdn = val;
+
+ return count;
+}
+
+static ssize_t trsmrcy_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%d\n", usb_timing.trsmrcy);
+}
+
+static ssize_t trsmrcy_store(struct kobject *kobj,
+ struct kobj_attribute *attr, const char *buf, size_t count)
+{
+ int ret, val;
+
+ ret = kstrtoint(buf, 10, &val);
+ if (ret < 0)
+ return ret;
+
+ if (val < 10)
+ usb_timing.trsmrcy = 10;
+ else
+ usb_timing.trsmrcy = val;
+
+ return count;
+}
+
+static ssize_t trstrcy_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%d\n", usb_timing.trstrcy);
+}
+
+static ssize_t trstrcy_store(struct kobject *kobj,
+ struct kobj_attribute *attr, const char *buf, size_t count)
+{
+ int ret, val;
+
+ ret = kstrtoint(buf, 10, &val);
+ if (ret < 0)
+ return ret;
+
+ if (val < 0)
+ usb_timing.trstrcy = 0;
+ else
+ usb_timing.trstrcy = val;
+
+ return count;
+}
+
+static struct kobj_attribute tdrsmdn_attr =
+ __ATTR(tdrsmdn, 0664, tdrsmdn_show, tdrsmdn_store);
+static struct kobj_attribute trsmrcy_attr =
+ __ATTR(trsmrcy, 0664, trsmrcy_show, trsmrcy_store);
+static struct kobj_attribute trstrcy_attr =
+ __ATTR(trstrcy, 0664, trstrcy_show, trstrcy_store);
+
+static struct attribute *attrs[] = {
+ &tdrsmdn_attr.attr,
+ &trsmrcy_attr.attr,
+ &trstrcy_attr.attr,
+ NULL
+};
+
+static struct attribute_group attr_group = {
+ .attrs = attrs,
+};
+
int usb_hub_init(void)
{
+ int retval;
+ struct kobject *usb_kobj;
+
if (usb_register(&hub_driver) < 0) {
printk(KERN_ERR "%s: can't register hub driver\n",
usbcore_name);
@@ -5279,6 +5369,16 @@ int usb_hub_init(void)
usb_timing.trstrcy = USB_TIMING_TRSTRCY_MIN;
}
+ usb_kobj = kobject_create_and_add("usb", kernel_kobj);
+ if (!usb_kobj)
+ return -ENOMEM;
+
+ retval = sysfs_create_group(usb_kobj, &attr_group);
+ if (retval) {
+ kobject_put(usb_kobj);
+ return retval;
+ }
+
/*
* The workqueue needs to be freezable to avoid interfering with
* USB-PERSIST port handover. Otherwise it might see that a full-speed
--
2.1.4
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