Re: [Discuss-gnuradio] X300 PCIe issues

[Marcus D. Leech]

On 04/27/2014 02:45 PM, Robert McGwier wrote:
> Backing off to Ubuntu 12.04.4 LTS was successful in getting the PCIe 
> Express interface to build, dkms the kernel module, start and 
> uhd_find_device sees the USRP x300.
>
> Now for the fun part.... using it.
>
> Finally:
>
> To all those entertaining PCIe interfacing,  do not install a later 
> version of kernel or distro than is KNOWN to support the interface. 
>  PCIe is most decidely NOT USB or GigE.  Ettus would not be using a 
> proprietary interface from NI with known working support for various 
> kernels if it were not necessary.  Having done multiple projects at 
> work with PCIe,  you use it when it is necessary and NEVER when it 
> isn't.  My application for the x3x0 series requires it.  I find all 
> the pieces of the needed documentation to make it all work NOT in one 
> place.  I will give a short summary today after I get my first app 
> going using the device.
>
> Thanks,
> Bob
I'll chime in as an occasional kernel and driver developer.  Developing 
code, like drivers or kernel extensions, that runs inside the kernel is
  a *royal pain in the posterior* in Linux.  While the "top side" API 
is very stable so that applications hardly *ever* experience API changes
  that require on-going tedious maintenance, the same cannot be said of 
code that runs in the kernel. Quite the contrary.  Linus and friends
  *routinely and regularly* change critical APIs within the kernel, 
sometimes even across minor version revs of the same codebase.  This makes
  maintaining drivers and other kernel code a complete and utter 
nightmare, and which is why often drivers are only guaranteed to work
  for specific kernel versions or kernel version series.  It's serious 
challenge, and it's not a road that should be gone down lightly....




--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org