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USB: Add a sysfs file to show LTM capabilities.

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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>
This commit is contained in:
Sarah Sharp 2012-07-05 17:17:24 -07:00
parent f74631e342
commit 024f117c2f
4 changed files with 30 additions and 7 deletions
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12
Documentation/ABI/testing/sysfs-bus-usb
View File

@ -208,3 +208,15 @@ Description:
such as ACPI. This file will read either "removable" or
"fixed" if the information is available, and "unknown"
otherwise.
What: /sys/bus/usb/devices/.../ltm_capable
Date: July 2012
Contact: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Description:
USB 3.0 devices may optionally support Latency Tolerance
Messaging (LTM). They indicate their support by setting a bit
in the bmAttributes field of their SuperSpeed BOS descriptors.
If that bit is set for the device, ltm_capable will read "yes".
If the device doesn't support LTM, the file will read "no".
The file will be present for all speeds of USB devices, and will
always read "no" for USB 1.1 and USB 2.0 devices.

7
drivers/usb/core/hub.c
View File

@ -2610,13 +2610,6 @@ static int check_port_resume_type(struct usb_device *udev,
return status;
}
static bool usb_device_supports_ltm(struct usb_device *udev)
{
if (udev->speed != USB_SPEED_SUPER || !udev->bos || !udev->bos->ss_cap)
return false;
return udev->bos->ss_cap->bmAttributes & USB_LTM_SUPPORT;
}
int usb_disable_ltm(struct usb_device *udev)
{
struct usb_hcd *hcd = bus_to_hcd(udev->bus);

10
drivers/usb/core/sysfs.c
View File

@ -253,6 +253,15 @@ show_removable(struct device *dev, struct device_attribute *attr, char *buf)
}
static DEVICE_ATTR(removable, S_IRUGO, show_removable, NULL);
static ssize_t
show_ltm_capable(struct device *dev, struct device_attribute *attr, char *buf)
{
if (usb_device_supports_ltm(to_usb_device(dev)))
return sprintf(buf, "%s\n", "yes");
return sprintf(buf, "%s\n", "no");
}
static DEVICE_ATTR(ltm_capable, S_IRUGO, show_ltm_capable, NULL);
#ifdef CONFIG_PM
static ssize_t
@ -649,6 +658,7 @@ static struct attribute *dev_attrs[] = {
&dev_attr_authorized.attr,
&dev_attr_remove.attr,
&dev_attr_removable.attr,
&dev_attr_ltm_capable.attr,
NULL,
};
static struct attribute_group dev_attr_grp = {

8
include/linux/usb.h
View File

@ -636,6 +636,14 @@ extern void usb_unlocked_enable_lpm(struct usb_device *udev);
extern int usb_disable_ltm(struct usb_device *udev);
extern void usb_enable_ltm(struct usb_device *udev);
static inline bool usb_device_supports_ltm(struct usb_device *udev)
{
if (udev->speed != USB_SPEED_SUPER || !udev->bos || !udev->bos->ss_cap)
return false;
return udev->bos->ss_cap->bmAttributes & USB_LTM_SUPPORT;
}
/*-------------------------------------------------------------------------*/
/* for drivers using iso endpoints */