On Sun, Apr 9, 2017 at 9:42 AM, Vít Šesták <groups-no-private-mail--contact-me-at--contact.v6ak....@v6ak.com> wrote: > > * DDC (PIN 15+16) – needed for getting the resolution etc., present even in > current version of VGA. While there is some attack surface, it seems to be > rather small.
Note that this is not strictly necessary for things to work though. Having the display device report its supported resolutions lets local config managers display a list of resolutions to choose from, but the VGA controller is free to just try to output whatever resolution it wants. The driver does not inform the display device of what resolution it is using via some out-of-band protocol, this information is trivially inferred by the number of pixel clocks between the front & back porches of the vsync & hsync signals. In 2017 you can't really damage devices by providing invalid signals (or I would have most definitely broken some things in the process of developing my own VGA controller), in practice the device usually just reports "signal out of range" or equivalent. Back-reporting via i2c is nice and convenient, but by no means required for things to work. You can just try best resolution you want, and if it doesn't work then keep trying others until it works. -- You received this message because you are subscribed to the Google Groups "qubes-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to qubes-users+unsubscr...@googlegroups.com. To post to this group, send email to qubes-users@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/qubes-users/CABQWM_DDJV1ORFeyDwabckwLZ9dYBWBbLeBZOuQCohV90vCuuA%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
