[ltp] 100mbit only when docked?

Henrique de Moraes Holschuh linux-thinkpad@linux-thinkpad.org
Thu, 09 Apr 2015 08:02:17 -0300

On Tue, Apr 7, 2015, at 06:54, Christoph Schmees wrote:
> Am 30.03.2015 um 01:38 schrieb Richard Neill:
> ...
> > You can check the hardware and cables of most ethernet devices by using 
> > TDR (time-domain reflectrometry). This sends pulses up the cable, and by 
> > timing it back, you can find which core is broken, and how
> > far away the break is. Annoyingly, I've never seen a Linux driver for 
> > this, but many thinkpad BIOSes support it as an advanced option within 
> > the network settings.
> > 
> to my knowledge TDR is pure hardware, and not even computer but
> high sophisticated electronics. Nothing w/ BIOS or Linux.

This hardware is included in several NIC/PHY chipsets.  AFAIK Linux lacks the driver functionality and the userspace/kernel ABI to expose it to userspace, but I could be wrong about this (I didn't hunt it down in Linux 4.0-rc to double-check).

The BIOS diagnostics code in several ThinkPads as well as some of the Windows drivers, OTOH, do have code to interface to the PHY's TDR probe, and do expose the functionality.

  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh