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Thread: Intel Thunderbolt Is Still A Pain For Linux Developers, Users

  1. #1
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    Default Intel Thunderbolt Is Still A Pain For Linux Developers, Users

    Phoronix: Intel Thunderbolt Is Still A Pain For Linux Developers, Users

    While Thunderbolt was promising from a technology perspective, it hasn't seen too much adoption outside of Apple systems and the Linux support is still plaguing developers and causing nightmares among Linux users...

    http://www.phoronix.com/vr.php?view=MTY0NDc

  2. #2
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    Default How is that different

    <..>it was wonderfully convenient connecting it to the Apple Thunderbolt Display with just having to connect a Thunderbolt cable and power cable.
    And how is that different from any other monitor? Except that in every other monitor you have various connections (VGA, DVI, HMDI, DisplayPort, etc.) for different devices and there is no need for converter like on Apple products.

    On every non Apple monitor basics are the same - power cable + video feed cable and that's it!

  3. #3
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    <...>it was wonderfully convenient connecting it to the Apple Thunderbolt Display with just having to connect a Thunderbolt cable and power cable.
    How is that different from any other (non Apple) display? Basically you have a display cable and power cable. How is Thunderbolt more convenient, than HDMI, DisplayPort, DVI or VGA?

  4. #4

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    Quote Originally Posted by ežiukas View Post
    How is that different from any other (non Apple) display? Basically you have a display cable and power cable. How is Thunderbolt more convenient, than HDMI, DisplayPort, DVI or VGA?
    Not having also Ethernet, audio (in cases where the monitor doesn't have a headphone jack and wanting to connect to an external speaker system), and USB primarily over the same cable.

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    Quote Originally Posted by ežiukas View Post
    How is that different from any other (non Apple) display? Basically you have a display cable and power cable. How is Thunderbolt more convenient, than HDMI, DisplayPort, DVI or VGA?
    It is more convenient because the TBolt cable carries both DisplayPort and PCI-Express to the display. This could be useful in the following ways:

    1: Display becomes a HUB (usb, Tbolt, card-reader, camera, etc) without additional cables
    2: Display can contain logic (you can put a graphics card in the display for example)
    3: Can be used as an interconnect.

    So when you think about TBolt, just think "DisplayPort + PCIExpress" in a single cable. The 'current' downsides are:

    Limited number of peripherals available
    Price of peripherals is high
    Price of cables is high.
    Speed is not fast enough for neat stuff (high performance external SLI/Crossfire) last time I checked.

  6. #6
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    Quote Originally Posted by ežiukas View Post
    And how is that different from any other monitor? Except that in every other monitor you have various connections (VGA, DVI, HMDI, DisplayPort, etc.) for different devices and there is no need for converter like on Apple products.

    On every non Apple monitor basics are the same - power cable + video feed cable and that's it!
    - your monitor can become a 1 cable laptop dock, with your peripherals connected to the display
    - even for a desktop, it's always nice to have sound jacks and usb hub behind the screen.
    - you can chain a second monitor from the first, instead of from the PC (closer => less cable)
    which are useful features. But yes, if your monitor does not do that, it is effectively useless.

  7. #7
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    Quote Originally Posted by russofris View Post
    It is more convenient because the TBolt cable carries both DisplayPort and PCI-Express to the display. This could be useful in the following ways:

    1: Display becomes a HUB (usb, Tbolt, card-reader, camera, etc) without additional cables
    2: Display can contain logic (you can put a graphics card in the display for example)
    3: Can be used as an interconnect.

    So when you think about TBolt, just think "DisplayPort + PCIExpress" in a single cable. The 'current' downsides are:

    Limited number of peripherals available
    Price of peripherals is high
    Price of cables is high.
    Speed is not fast enough for neat stuff (high performance external SLI/Crossfire) last time I checked.
    you're forgetting an extremely serious downside: thunderbolt ports are completely insecure due to their direct PCI-e access. which means that a malicious piece of hardware or even one that just has badly coded firmware can screw over your entire system at the hardware level. And this isn't just a theoretical problem, there are plenty of cases that have shown up in tech news where some hardware manufacturer or another was unknowingly distributed malware because a disgruntled or paid off employee decided to compromise the hardware or driver disk.

    Further you can do most of the same using just 1 additional USB cable, of the type everyone has lying around somewhere, however putting the GPU in the display is honestly a horrible idea. Not only is a monitor significantly thermally constrained which means that at best you'll be using laptop parts but it becomes a non-upgradeable component (even assuming they make it replacable you're going to have to go to somewhere like Ebay of all places to get one), and you're very significantly increasing the latency between the parts that need as low latency as possible to decrease the latency between the parts that are far less sensitive to latency, and you're increasing the price of the display significantly (because now you're also having to pay the price of a laptop GPU).

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    Quote Originally Posted by Luke_Wolf View Post
    you're forgetting an extremely serious downside: thunderbolt ports are completely insecure due to their direct PCI-e access. which means that a malicious piece of hardware or even one that just has badly coded firmware can screw over your entire system at the hardware level.
    Referring to DMA access as "completely insecure" is a bit misleading, yes? After all, every Ultra ATA, SATA, SCSI, SAS, and Firewire device in existence uses DMA mode access, no different from Thunderbolt. DMA mode performs way better than PIO mode, especially for bulk data transfers. When you're talking bulk data transfers (i.e. hard drives) it's silly and stupid to use PIO mode. It's the reason that Firewire 400 hard drives delivered much better real world performance as compared to USB 2.0 hard drives, despite Fw400's lower bit rate (400 Mbit vs. USB's 480 Mbit).

    Another downside to PIO mode, is the requirement for drivers. You need to write drivers for all the different OS's, in order to use those devices. That means your dependent on the vendor to maintain those drivers. In Windows land, how many perfectly good USB devices, printers, scanners, etc. have been tossed in the trash because the vendor wrote a Win9x driver but then never bothered to release a W2k or XP driver? Millions I'd wager. Less of an issue on Linux, assuming FOSS drivers get written.

    Personally I wish Firewire had developed beyond Fw800. There were plans for Fw1600 and Fw3200 at one time, which would have kept it competitive. All my external hard disks, scanners, cameras, and audio mixers are all Firewire.

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    Quote Originally Posted by torsionbar28 View Post
    Referring to DMA access as "completely insecure" is a bit misleading, yes? After all, every Ultra ATA, SATA, SCSI, SAS, and Firewire device in existence uses DMA mode access, no different from Thunderbolt.
    Except here's the difference (ignoring firewire which is as stupid as thunderbolt imo) an HDD is inherently a trusted computing device because you need to have internal storage and you're storing your data on it after all, and things that are inside of your computer (cpu, gpu, networking devices, etc) are things you inherently *have* to trust in order for you to have a computer, however there is no reason that that trusted computing base should be extended to external devices, particularly not for all external devices.

  10. #10
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    Quote Originally Posted by torsionbar28 View Post
    Referring to DMA access as "completely insecure" is a bit misleading, yes? After all, every Ultra ATA, SATA, SCSI, SAS, and Firewire device in existence uses DMA mode access, no different from Thunderbolt. DMA mode performs way better than PIO mode, especially for bulk data transfers. When you're talking bulk data transfers (i.e. hard drives) it's silly and stupid to use PIO mode. It's the reason that Firewire 400 hard drives delivered much better real world performance as compared to USB 2.0 hard drives, despite Fw400's lower bit rate (400 Mbit vs. USB's 480 Mbit).
    The big difference is that SATA, etc. are internal ports (eSATA ports are pretty rare, and every mass deployment I've seen has them blocked off if they were present). Firewire is a completely different matter - the only reason it doesn't get more attention is because it's so uncommon. The only way to protect against that attack on Linux is to disable DMA or blacklist the kernel module.[1] That's an unacceptable vulnerability for any external facing interface.

    DMA might yield better performance, but giving any device plugged in DMA access is utterly retarded from a security perspective. At the very least, you want some confirmation phase where the user whitelists the device before it can be granted DMA. This check could be implemented in the DMA controller to avoid any overhead, with the kernel authorising new devices. Each device would need a unique ID to prevent malicious devices from cloning known good IDs, but that shouldn't be too hard to implement given that we already have similar systems for MAC addresses and USB.



    [1] http://www.breaknenter.org/projects/inception/

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