USB: Add a sysfs file to show LTM capabilities.
USB 3.0 devices can optionally support Latency Tolerance Messaging (LTM). Add a new sysfs file in the device directory to show whether a device is LTM capable. This file will be present for both USB 2.0 and USB 3.0 devices. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
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@ -208,3 +208,15 @@ Description:
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such as ACPI. This file will read either "removable" or
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"fixed" if the information is available, and "unknown"
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otherwise.
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What: /sys/bus/usb/devices/.../ltm_capable
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Date: July 2012
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Contact: Sarah Sharp <sarah.a.sharp@linux.intel.com>
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Description:
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USB 3.0 devices may optionally support Latency Tolerance
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Messaging (LTM). They indicate their support by setting a bit
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in the bmAttributes field of their SuperSpeed BOS descriptors.
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If that bit is set for the device, ltm_capable will read "yes".
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If the device doesn't support LTM, the file will read "no".
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The file will be present for all speeds of USB devices, and will
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always read "no" for USB 1.1 and USB 2.0 devices.
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@ -2610,13 +2610,6 @@ static int check_port_resume_type(struct usb_device *udev,
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return status;
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}
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static bool usb_device_supports_ltm(struct usb_device *udev)
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{
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if (udev->speed != USB_SPEED_SUPER || !udev->bos || !udev->bos->ss_cap)
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return false;
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return udev->bos->ss_cap->bmAttributes & USB_LTM_SUPPORT;
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}
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int usb_disable_ltm(struct usb_device *udev)
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{
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struct usb_hcd *hcd = bus_to_hcd(udev->bus);
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@ -253,6 +253,15 @@ show_removable(struct device *dev, struct device_attribute *attr, char *buf)
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}
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static DEVICE_ATTR(removable, S_IRUGO, show_removable, NULL);
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static ssize_t
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show_ltm_capable(struct device *dev, struct device_attribute *attr, char *buf)
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{
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if (usb_device_supports_ltm(to_usb_device(dev)))
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return sprintf(buf, "%s\n", "yes");
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return sprintf(buf, "%s\n", "no");
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}
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static DEVICE_ATTR(ltm_capable, S_IRUGO, show_ltm_capable, NULL);
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#ifdef CONFIG_PM
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static ssize_t
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@ -649,6 +658,7 @@ static struct attribute *dev_attrs[] = {
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&dev_attr_authorized.attr,
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&dev_attr_remove.attr,
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&dev_attr_removable.attr,
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&dev_attr_ltm_capable.attr,
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NULL,
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};
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static struct attribute_group dev_attr_grp = {
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@ -636,6 +636,14 @@ extern void usb_unlocked_enable_lpm(struct usb_device *udev);
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extern int usb_disable_ltm(struct usb_device *udev);
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extern void usb_enable_ltm(struct usb_device *udev);
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static inline bool usb_device_supports_ltm(struct usb_device *udev)
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{
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if (udev->speed != USB_SPEED_SUPER || !udev->bos || !udev->bos->ss_cap)
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return false;
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return udev->bos->ss_cap->bmAttributes & USB_LTM_SUPPORT;
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}
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/*-------------------------------------------------------------------------*/
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/* for drivers using iso endpoints */
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