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How to programatically determine the usb port speed in embedded devices running the Linux kernel?
You can read /sys/bus/usb/devices/usb?/speed - it'll give you the bus speed of the root hub(s) in Mbps: either 1.5, 12, 480, 5000 or 10000. The first two indicate USB1 (low speed or full speed), the third USB2 and the fourth and fifth USB3.
This rather depends on were the code that needs the information is running. If you want to modify a kernel USB device drivers behavior based on connection speed then the usb_device struct that passed to the driver by the USB subsystem contains a speed enumeration. If you want an application in user space to detect the devices connection speed then try walking the /sys/bus/usb tree you should be able to identify your USB device by checking the idProduct and idVendor entries. Once you have a match then the speed entry will give you what you need.
If you have multiple devices connected then you might need to figure a way to match USB id to specific device. Generally USB to device mappings vary on any hot plug support present whether the device supplies a serial number and the sub system that abstracts the functionality provided by the USB device.
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Closed 1 year ago.
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My laptop used to come with windows 10, but then I decided to install ubuntu on it instead. Now I would like to install windows 10. Is there way to get windows 10 back?
First you will need a bootable USB - a USB flash drive that has at least 16GB of space (there are free programs that you will find available on internet to make the USB bootable), download Windows 10 ISO file and add to the USB.
Alter the BIOS sequence on your PC so your USB device is first. In most instances, the BIOS will usually not be automatically set to your device. If you skip this step, your computer will start regularly from your hard drive instead of getting boot information from your USB device, then follow the steps to install the windows OS.
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Closed 7 years ago.
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I just received a pi 2 with sd card preloaded with NOOBS. I also have an hdmi cable and wifi dongle for it.
I wanted to begin using the pi 2 but do not have a spare monitor to connect it to. I was hoping to be able to connect to my macbook pro (Late 2013 - hence has HDMI) either via HDMI or wifi or ssh so that I could essentially use the macbook's display and keyboard to utilize the pi 2. How is this done, suggestions, recommended way of doing it?
Thank you
I guess that, for the first time, you will need to have a monitor, keyboard and mouse and a LAN connection in order to check everything is going fine.
After you set up everything, you can go on using SSH & SFTP. You should setup x11vnc and you can be really good without any peripheral after that, you will only a LAN connection. If you have a WiFi Dongle for the PI, you also can be unplugged from the Ethernet Cable.
If you want to try, just plug the RPi and try to make an SSH, by checking your LAN devices. If you can, then you dont need anything else.
Cheers...
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Closed 8 years ago.
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I am aware that the USB drive can be damaged if you disconnect it without ejecting it first, but is it possible to damage the computer itself?
I've disconnected my USB drive from my Macbook Pro Retina and the OS gave me a warning about an incorrectly unplugged USB drive. Can this damage the computer?
You won't damage the computer unless you remove the drive violently enough to cause physical damage to the USB connector -- that said, you might cause problems with the file structure on the USB drive, which might cause the drive to become read-only or even cause loss of data, and some operating systems (in my experience, older version of Windows, but I have little experience with Mac OS) may become confused and be unable to remount the same USB volume until you restart the computer.
I have done that countless times and I have never noticed any damage, but I have used PCs only, no MACs.
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Closed 8 years ago.
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It appears that the destination MAC address is added for routing purposes. But what is the purpose of including a source MAC address in a packet?
One purpose, besides telling the destination host where to send the reply, is i.e. in switches. They use the source address to identify the address of the system on a specific port. Next time they see that address as the destination, they know where to send the packet. Otherwise, the packet would need to be sent to all ports, making the switch perform not much better than a simple hub.
One use of source MAC addresses is for switches to discover which port a MAC address is connected to.
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I want to know how a device node is created when a hardware is connected to the system.
Information that I know:
When a piece of hardware is connected to the system, the device name is compared with the driver name, if it matches, then probe is called.
Info I wish to know:
At which point is the device node created and who is creating it? (In other words, I want to know where mknod is happening?)
This one thing is bugging my mind from so many months. Please tell me programatically where is this happening.
On most (but not all!) Linux systems this is handled by Udev.
It is notified of the new hardware through a netlink socket. It then creates the device node, based on its configuration.