On Sun 17 Feb 2019 at 21:34:44 +0100, Rhialto wrote:
> I have an external harddisk, like so: (output from usbdevs -v)
>
> Controller /dev/usb0:
> addr 0: super speed, self powered, config 1, xHCI Root Hub(0x0000), vendor 8086(0x8086), rev 1.00(0x0100)
> port 1 addr 9: super speed, power 224 mA, config 1, Elements 25A1(0x25a1), Western Digital(0x1058), rev 10.14(0x1014), serial xxxxxxxxxxxxxxxxxxxxxxxx
To make things more interesting, I connected it to a laptop which has
USB 2, not 3, and under Linux "lsusb -v" says
bmAttributes 0x80
(Bus Powered)
MaxPower 500mA
On the same laptop, with NetBSD 8, also 500 mA:
Controller /dev/usb7:
addr 1: high speed, self powered, config 1, EHCI root hub(0x0000), vendor 8086(0x8086), rev 1.00(0x0100)
port 1 addr 2: high speed, power 500 mA, config 1, Elements 25A1(0x25a1), Western Digital(0x1058), rev 10.14(0x1014), serial xxxxxxxxxxxxxxxxxxxxxxxx
When I try the same on the original computer in a USB 2 port, I get the
same result.
On a MacBook (which does have USB 3), "System Information" says
"Current Available (mA): 900" and "Current Required (mA): 896".
And on a laptop with Linux and USB 3 ports, the same "224 mA" number is
shown by lsusb -v.
So there seems some confusion about the number, which supposedly is
reported by the device and simply believed by the computer.
So inspired by seeing "500 mA" on USB-2 ports, I plugged the disk into
a USB-2 port on the original computer, and I don't see the symptoms
(yet??) that made me think that there was a power problem.
Can anyone shed some light on this?
-Olaf.
--
___ Olaf 'Rhialto' Seibert -- "What good is a Ring of Power
\X/ rhialto/at/falu.nl -- if you're unable...to Speak." - Agent Elrond
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