20 ms·

I remember seeing somewhere that in the beginning of Linux on the Nintendo Switch that people destroyed their displays by raising the brightness bar too high.

• gambiting 4y ago
  Well because like you said - it's a general purpose controller. Maybe it can drive any display accepting voltage input between 5 and 12V, which means that you can use it with a display that only supports 5-8V range - you just limit the range in software and make sure the user can't select anything about 8V. But if a device is hacked and the controller sent direct commands, then of course it could lead to issues.
  • esperent 4y ago
    Well that's fair for the switch. It's a locked down platform and sold as such. If you hack, you're doing so at your own risk. But is that really the case for these laptops? Seems kind of negligent from the manufacturer if so.
  • xani_ 4y ago
    LEDs are current driven, not voltage driven. It's still weird as most controllers have the current set via resistor (either the value of inline resistor used for current measurement, or separate one), why wouldn't you set that to the max one for the panel ? edit: https://www.diodes.com/assets/Datasheets/AP3019A.pdf https://www.diodes.com/assets/Datasheets/AP3019A.pdf example of simple one. The value of the single resistor decides the max current.
• pas 4y ago
  because the whole industry [and by extension the whole world] is built on a throne of lies, shit, pain, and weapons-grade idiocy. there's absolutely no safety mindset for anything behind the cover. if it's industrial, just put a big sticker on it, write something about it in the mandatory occupational hazards training kit, maaaaaaaybe consider adding a fence, but it's fine anyway. if it's consumer stuff? well, as long as kids won't choke on it, it's A-OK. especially if it comes to electronics. just write in the user's guide that always disconnect it from the mains when not in use, if used improperly that's on you, and don't ever think about opening it. that only for professionals who are trained in the dark arts of handling this exact piece of immanetized hell-forged eschaton housed in a convenient beige plastic. adding a voltage limiter between the LCD panel and the input would cost money. designing it would cost money. adding an analog limiter on the regulator would cost money (plus setting it mechanically is very expensive compared to flashing on some firmware), compartmentalizing the software - by having a segment that's set at assembly that contains the physical properties of connected parts, which communicates the operational limits, and the other segment which can be set via software - would also cost a lot of money.
  • capableweb 4y ago
    > there's absolutely no safety mindset for anything behind the cover. As a counter-point: One persons "safety" is another persons "limitation". Sometimes it's good that things are generally protected but you can break through the protections somewhat.
    • pas 4y ago
      I'm not advocating for filling out the whole insides with epoxy. (Quite the contrary, I think it'd be great to have better markings on components, and have data sheets - and schematics - for them readily available. I mean it's ridiculous that the whole IP protection legal machinery is justified in the name of incentivizing invention and new works, but in practice all we got is cheaper and cheaper copies/derivatives of the same noname things.)
    • collegeburner 4y ago
      facts, if there was a regulator some hackernews would be on here complaining about how it's "not hackable" or whatever.
  • throwawaylinux 4y ago
    Lots of real time, safety critical, and control systems rely on software and don't have mechanical or hard wired electronic interlocks or fallbacks. That doesn't make it worse than alternatives. You could hack the firmware and make the device behave out of spec, but you could also hack the hardware. If you bypassed your voltage limiter on the board then you could blow it up too.
    • GTP 4y ago
      And there is the crucial difference: you would need to bypass the voltage limiter on purpose, your display wouldn't be ruined by mistake just by putting a slider to the maximum possible value.
      • throwawaylinux 4y ago
• ablob 4y ago
  If its about hardware security measures it may be its spatial cost. Having each circuit / subcircuit bring its own safety is certainly gonna be subobtimal when optimizing for size. On the software side I reckon the driving circuit is the deciding factor, which a vendor (of displays) can't control.
• ajsnigrutin 4y ago
  > How come these things are not secured against at the LCD controller side? Why would a general purpose controller ne designed to accept e.g. too high voltage levels? Why would they be secured there? The device doesn't allow setting any of the dangerous settings, so noone will break their displays this way. Look at cars for example... pretty much cars have systems in place not to overheat (thermostatic valves, fans, etc.). Most even have code to go into limp mode and turn off if they overheat. Now imagine someone taking the ECU out of the car, installing gentoo on it, putting it back in, and forget to write a script to check the temperature and turn on the fans when needed... the car would probably work ok when driving high airflow) but when stopped, it would heat, overheat and eventually something would break down. Do we need some kind of a hardware system in our cars to turn on the fans, or something that turns off the main relay, because someone decided to hack the software and forgot to implement sotware limits and checks?
  • hulitu 4y ago
    Cars are mostly immune to such things. Mostly due to previous experience which has showed that SW alone will not protect hardware.
    • ajsnigrutin 4y ago
      So, what exactly stops the car when it gets too hot? Or when there's no oil? (except the eventual engine failure)
      • tremon 4y ago
        The driver.
      • hulitu 4y ago
        The car is _designed_ so that it doesn't get to hot. If, despite this, it gets hot it will be stopped. Now, those are the requirements and some suppliers might disregard them with the prize of their liability.
        • 4y ago
• deleted 4y ago
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• MisterTea 4y ago
  > Why would a general purpose controller be designed to accept e.g. too high voltage levels? Pragmatic design decisions. My bet is they decided that adding voltage regulation was unnecessary since they can limit it via software which they have control. Adding voltage regulation would increase the component count which takes up board space and lengthens the BOM (bill of materials.)
• xattt 4y ago
  This reminds me of installing uLinux on a Palm IIIxe around 2000-2001. During reboot, one of the transparent diagonal LCD traces behind the LCD went black for several seconds and then faded back to clear. I thought I fried the thing, but it went away it on its own and the display continued to work. I couldn’t figure out a mechanism for causing it to happen, but this explains it.
• PragmaticPulp 4y ago
  > How come these things are not secured against at the LCD controller side? Because we make generic LCD controllers that can service a wide range of panels. Using generic parts with adjustable outputs is standard practice. It keeps prices down, keeps supply chains flowing, and makes it easier to design new systems around common parts. It also reduces the amount of waste because common parts can be re-used in new designs and resold if unused. Many things around you are controlled by software settings without separate hardware limits to keep them in check. If you have an enthusiast motherboard, you can reboot right now into the BIOS and set the CPU and RAM voltages to numbers that will fry your chips in short order if you want, and it won't stop you at the hardware level. Generic parts with a wide output range are great, but it requires care and attention to make sure the software is providing the right settings.
  • deleted 4y ago
    [deleted]
• megous 4y ago
  Rising brightness too high has nothing to do with LCD controller.
• xani_ 4y ago
  First example: LED used as flash in phones. The simplest hardware design is just running it at say 10% max in flashlight mode but allowing for short bursts of overdrive for flashing. The LED is big enough to handle short bursts, but not thermally cooled well enough to work at full power all the time. So you rely on firmware/software to do its job instead of having specialised hardware controller that's only job would be to make sure LED isn't on on 100% for more than say half a sec. You control software so you don't GAF, but people putting custom one have to take same amount of care Second example: You're an engineer and need to drive a backlight. You can * slap a constant-current controller (buck or two of parts) so 100% is a maximum safe level all while regulating it at >90% efficiency * slap a high value resistor costing $0.01 so 100% is maximum level is safe but you lose a lot of power in the resistor * slap a low value resistor then just drive it at 20% duty cycle and waste less heat in resistor all while still costing $0.01 They just most likely picked 3rd. Or picked 1st and misengineered the limits I guess...
  • megous 4y ago
    Phones use flash LED controllers that limit the time the LED is able to turn on in high power mode. Though apparently you can misdesign the HW with these, too, as I've recently discovered.
• Gordonjcp 4y ago
  Because you don't know what the final design spec might need to be, under all circumstances. I've got a board design that's used in production that the moment where - depending on configuration - it could blow the device it's connected to up in about three seconds if you set it to full power in normal operation. It's designed to go that high, because it may be running from a very degraded power supply and it may be necessary to "kick" the actuator it controls quite hard with short bursts of full power to unstick it as it wears.