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The buried lede: > Therefore, it is impossible to ever replace the HDMI blob used by this device. The device could be used without this blob, but you then fore

by kibwen 4y ago

The buried lede: > Therefore, it is impossible to ever replace the HDMI blob used by this device. The device could be used without this blob, but you then forego use of the HDMI (or DisplayPort) functionality. > Note about the MNT Reform: The MNT Reform went out of its way to avoid relying on this blob for its internal display. Rather than doing the obvious thing and connecting the i.MX8M's DisplayPort interface to the Embedded DisplayPort (eDP) display panel, they connected the internal display by using the i.MX8M's MIPI DSI interface (which is unaffected by this blob) to connect to a MIPI DSI to eDP converter chip, and then to the display (indeed, the fact that they went out of their way to ensure people can use the laptop without the blob certainly warrants praise). The external HDMI port can't be used without the blob, however.

pabs3 4y ago
What blobs does the MIPI DSI to eDP converter chip run?
- nrclark 4y ago
  Some, probably. But that firmware is self-contained to the converter chip, and doesn't have the ability to interact with your CPU's various subsystems. The i.MX8's HDMI core has independent access to the DDR memory, peripheral buses, timers, DMAs, and who knows what else. It's probably even running an RTOS of some kind, which might or might not include network drivers. Malicious firmware could compromise the security of your entire device. It's kind of the same problem that some folks have with Intel's IME. It could be fine and secure. Or maybe not, we just don't know. Nobody's saying that the i.MX8's HDMI firmware is malicious. It's probably fine. But we also don't know, because we can't inspect it. So if you were designing that chip into a security-critical setting, you'd have to wonder what might be running without your knowledge.
seba_dos1 4y ago
Just a note: i.MX8MQ has only two display interfaces - one (less power hungry) is only capable to drive MIPI-DSI, and another bigger one that can drive either MIPI-DSI or HDMI/DP. If a i.MX8MQ system wants to support both eDP and external HDMI at the same time, it simply has to use MIPI-DSI with a converter on one of its outputs, there's no way around it.

by kibwen 4y ago

pabs3 4y ago

What blobs does the MIPI DSI to eDP converter chip run?

nrclark 4y ago
Some, probably. But that firmware is self-contained to the converter chip, and doesn't have the ability to interact with your CPU's various subsystems. The i.MX8's HDMI core has independent access to the DDR memory, peripheral buses, timers, DMAs, and who knows what else. It's probably even running an RTOS of some kind, which might or might not include network drivers. Malicious firmware could compromise the security of your entire device. It's kind of the same problem that some folks have with Intel's IME. It could be fine and secure. Or maybe not, we just don't know. Nobody's saying that the i.MX8's HDMI firmware is malicious. It's probably fine. But we also don't know, because we can't inspect it. So if you were designing that chip into a security-critical setting, you'd have to wonder what might be running without your knowledge.

seba_dos1 4y ago

Just a note: i.MX8MQ has only two display interfaces - one (less power hungry) is only capable to drive MIPI-DSI, and another bigger one that can drive either MIPI-DSI or HDMI/DP. If a i.MX8MQ system wants to support both eDP and external HDMI at the same time, it simply has to use MIPI-DSI with a converter on one of its outputs, there's no way around it.