6 ms·

Just an FYI SPI is a pretty standard interface in the embedded world

by emgeee 10y ago

userbinator 10y ago
True, but SPI is really just referring to the physical layer protocol while the layers above can vary considerably and be proprietary. The only thing that's constant is that it is a synchronous serial protocol. It's not like USB which defines device classes and the higher-level layers of the stack, or PS/2 where e.g. all PS/2 keyboards or mice are expected to have an identical basic set of functionality and behaviour. There are certainly proprietary "vendor-specific" extensions to those, but e.g. it's almost a given that if you plug in a USB keyboard, all the standard QWERTY keys should work effortlessly; and while there may be extensions like displays and touchbars that require specific drivers, the core functionality doesn't change. If I understand correctly, what Apple did here is invent their own protocol for the keyboard which is completely different from what any PC or earlier Macs have, thus the lack of any functionality from Linux. And given how crucial a keyboard is to being able to do anything with the computer, it's no wonder this has caused much consternation. I think many people are used to the idea that even if the OS does not provide drivers for specific devices, basic functionality like keyboard, mouse, and video (even if it's something like a VGA 640x480 16 colours mode) should still be present --- partly to enable "bootstrapping" into more functionality by installing and troubleshooting the drivers.
- geocar 10y ago
  > I think many people are used to the idea that even if the OS does not provide drivers for specific devices, basic functionality like keyboard, mouse, and video (even if it's something like a VGA 640x480 16 colours mode) should still be present --- partly to enable "bootstrapping" into more functionality by installing and troubleshooting the drivers. Then I think people need to step back and appreciate that this "basic functionality" is actually really expensive in terms of price, space, power and performance. Would they really pay more for Apple hardware if it booted up with a full internal USB or a PS/2? What if it made the laptop heavier? Shortened the battery life? These things are very important to me: I wouldn't buy a heavier Mac. Could this be mitigated with custom ASICs? Or a new power switch and some extra power controllers (e.g. a soft switch to turn off the fallback 8042 and start using the faster more sensible SPI interface)? Perhaps, but someone has to pay for it. Moaning about things that don't make sense to change -- that someone just doesn't like, just makes that someone unhappy.
  - userbinator 10y ago
    Could this be mitigated with custom ASICs? Or a new power switch and some extra power controllers (e.g. a soft switch to turn off the fallback 8042 and start using the faster more sensible SPI interface)? Perhaps, but someone has to pay for it. PS/2 has not been implemented with a real 8042 for a very long time. Standard laptop ECs which are cheap and widely available have optimised dedicated hardware to handle the protocol. Speed is not a problem either, because this doesn't need to be a physical PS/2 interface with a separate keyboard on the end of it --- in the designs I've seen, the EC scans the key matrix itself and just provides a PS/2 software interface. It really doesn't matter what the physical interface on a laptop is, since the software interface is what's important here; Apple could've used something similar to PS/2 but increased the clock rate to whatever they needed, and it'd still look the same and be compatible to existing software. USB is not a good idea from a power perspective since it is a polled bus and there's plenty of additional unneeded complexity throughout the whole stack, but PS/2 is interrupt-driven and extremely low-power. In fact, it is a synchronous serial protocol just like SPI, so what appears to have happened with these MacBooks is that Apple basically reinvented PS/2 in their own "Think Different" way.
    - mjg59 10y ago
      >In fact, it is a synchronous serial protocol just like SPI, so what appears to have happened with these MacBooks is that Apple basically reinvented PS/2 in their own "Think Different" way. Ugh. Almost everybody uses SPI for touchpads these days, although they frequently also provide a PS/2 compatibility mode. Apple don't care about working with stock operating systems other than their own (the Bootcamp installer injects additional drivers for Windows), so they decided not to bother.
    - geocar 10y ago
      > Apple could've used something similar to PS/2 but increased the clock rate to whatever they needed, and it'd still look the same and be compatible to existing software. If you deliver a byte per interrupt to be compatible with PS/2 then your system has to wake up more frequently than a DMA/SPI interface. > USB … is a polled bus > PS/2 is interrupt-driven and low-power enough for me. This is wrong. USB and PS/2 both deliver an interrupt when there is data available. USB can be configured to directly store the data in memory, so that in the ISR the operating system simply scans memory. PS/2 on the other hand has to be polled inside the ISR, whether there is data available or not. Not a problem for a keyboard, but touchpads send a lot of data (of course, this is why everyone uses SPI for touchpads) > It really doesn't matter what the physical interface on a laptop is, since the software interface is what's important here This is a common, but fundamental misunderstanding of how software and hardware work. Hardware is not mere programmable matter, it has wires and current, and those wires take up space, and that current draws down your battery. A lot of laptop vendors have to include "compatibility chips" that take up space and draw down battery because they don't control the software, but if they did control the software they could make their users happier.
WayneBro 10y ago
Wheels are pretty standard on cars too. Shouldn't every computer have wheels?

Just an FYI SPI is a pretty standard interface in the embedded world

by emgeee 10y ago

Just an FYI SPI is a pretty standard interface in the embedded world

True, but SPI is really just referring to the physical layer protocol while the layers above can vary considerably and be proprietary. The only thing that's constant is that it is a synchronous serial protocol. It's not like USB which defines device classes and the higher-level layers of the stack, or PS/2 where e.g. all PS/2 keyboards or mice are expected to have an identical basic set of functionality and behaviour. There are certainly proprietary "vendor-specific" extensions to those, but e.g. it's almost a given that if you plug in a USB keyboard, all the standard QWERTY keys should work effortlessly; and while there may be extensions like displays and touchbars that require specific drivers, the core functionality doesn't change. If I understand correctly, what Apple did here is invent their own protocol for the keyboard which is completely different from what any PC or earlier Macs have, thus the lack of any functionality from Linux. And given how crucial a keyboard is to being able to do anything with the computer, it's no wonder this has caused much consternation. I think many people are used to the idea that even if the OS does not provide drivers for specific devices, basic functionality like keyboard, mouse, and video (even if it's something like a VGA 640x480 16 colours mode) should still be present --- partly to enable "bootstrapping" into more functionality by installing and troubleshooting the drivers.

geocar 10y ago
> I think many people are used to the idea that even if the OS does not provide drivers for specific devices, basic functionality like keyboard, mouse, and video (even if it's something like a VGA 640x480 16 colours mode) should still be present --- partly to enable "bootstrapping" into more functionality by installing and troubleshooting the drivers. Then I think people need to step back and appreciate that this "basic functionality" is actually really expensive in terms of price, space, power and performance. Would they really pay more for Apple hardware if it booted up with a full internal USB or a PS/2? What if it made the laptop heavier? Shortened the battery life? These things are very important to me: I wouldn't buy a heavier Mac. Could this be mitigated with custom ASICs? Or a new power switch and some extra power controllers (e.g. a soft switch to turn off the fallback 8042 and start using the faster more sensible SPI interface)? Perhaps, but someone has to pay for it. Moaning about things that don't make sense to change -- that someone just doesn't like, just makes that someone unhappy.
- userbinator 10y ago
  Could this be mitigated with custom ASICs? Or a new power switch and some extra power controllers (e.g. a soft switch to turn off the fallback 8042 and start using the faster more sensible SPI interface)? Perhaps, but someone has to pay for it. PS/2 has not been implemented with a real 8042 for a very long time. Standard laptop ECs which are cheap and widely available have optimised dedicated hardware to handle the protocol. Speed is not a problem either, because this doesn't need to be a physical PS/2 interface with a separate keyboard on the end of it --- in the designs I've seen, the EC scans the key matrix itself and just provides a PS/2 software interface. It really doesn't matter what the physical interface on a laptop is, since the software interface is what's important here; Apple could've used something similar to PS/2 but increased the clock rate to whatever they needed, and it'd still look the same and be compatible to existing software. USB is not a good idea from a power perspective since it is a polled bus and there's plenty of additional unneeded complexity throughout the whole stack, but PS/2 is interrupt-driven and extremely low-power. In fact, it is a synchronous serial protocol just like SPI, so what appears to have happened with these MacBooks is that Apple basically reinvented PS/2 in their own "Think Different" way.
  - mjg59 10y ago
    >In fact, it is a synchronous serial protocol just like SPI, so what appears to have happened with these MacBooks is that Apple basically reinvented PS/2 in their own "Think Different" way. Ugh. Almost everybody uses SPI for touchpads these days, although they frequently also provide a PS/2 compatibility mode. Apple don't care about working with stock operating systems other than their own (the Bootcamp installer injects additional drivers for Windows), so they decided not to bother.
  - geocar 10y ago
    > Apple could've used something similar to PS/2 but increased the clock rate to whatever they needed, and it'd still look the same and be compatible to existing software. If you deliver a byte per interrupt to be compatible with PS/2 then your system has to wake up more frequently than a DMA/SPI interface. > USB … is a polled bus > PS/2 is interrupt-driven and low-power enough for me. This is wrong. USB and PS/2 both deliver an interrupt when there is data available. USB can be configured to directly store the data in memory, so that in the ISR the operating system simply scans memory. PS/2 on the other hand has to be polled inside the ISR, whether there is data available or not. Not a problem for a keyboard, but touchpads send a lot of data (of course, this is why everyone uses SPI for touchpads) > It really doesn't matter what the physical interface on a laptop is, since the software interface is what's important here This is a common, but fundamental misunderstanding of how software and hardware work. Hardware is not mere programmable matter, it has wires and current, and those wires take up space, and that current draws down your battery. A lot of laptop vendors have to include "compatibility chips" that take up space and draw down battery because they don't control the software, but if they did control the software they could make their users happier.

WayneBro 10y ago

Wheels are pretty standard on cars too. Shouldn't every computer have wheels?