notes about "HANDS-ON PROJECTS FOR THE LINUX GRAPHIC SUBSYSTEM - Karayiannis, Christos"

two machines:
irbis - with integrated graphic, i915, wayland, Ubuntu 22.04
acer - with AMD graphic, radeon, Xorg, Ubuntu 18.04

location 122:
in irbis ctr-alt-fn-f1 (something like "refresh")
     ctr-alt-fn-f2 (regular display)
             f2-f6 (text-based)
     i am succesfully tried this: sudo /usr/bin/Xorg :2 vt7 and with ctr-alt-fn-f7 i saw this display

location 138:
for remote experiments
ssh nik0@192.168.0.16 DISPLAY=1.0 xterm &

location 192:
about xorg.conf, i m found this(https://askubuntu.com/questions/4662/where-is-the-x-org-config-file-how-do-i-configure-x-there):
/*
The xorg.conf does not exist by default any more. You CAN create one though.

Boot into recovery mode and select Root Shell. Then run:

$X -configure

Then:

$cp /root/xorg.conf.new /etc/X11/xorg.conf

Reboot and you can edit the new Xorg.conf.
*/
also in new versions xorg.conf is xorg.conf.d and it is manual: https://www.x.org/releases/current/doc/man/man5/xorg.conf.5.xhtml

location 330:
we speak about finding driver name, i can found in xorg.conf this information but i found more usefull this:

lspci -k | grep -EA3 'VGA|3D|Display'

from: https://www.intel.com/content/www/us/en/support/articles/000005520/graphics.html
this output also have a driver name and device info

in my irbis pc  i have driver i915 it is integrated graphics driver
in acer pc i have driver radeon

source for i915: https://github.com/torvalds/linux/tree/master/drivers/gpu/drm/i915
source for radeon: https://github.com/torvalds/linux/tree/master/drivers/gpu/drm/radeon

how i understand x must detect device(only certain type):
03 00 00  - just graphics(include integrated)
03 xx xx  - for pci devices

location 345:
we speak about xorg-server.h but in my version it is generated file not static xorg-server.h.in

location 398:
in irbis pc - not launched Xorg but launched Wayland(with two processes)
in acer pc - Xorg launched

location 412:
in acer pc: AMD BDF = 01:00.0

location 509:
in irbis pc  i have anon_inode:i915.gem - GEM (graphics execution manager) https://01.org/linuxgraphics/blogs/vivijim/2012/i915/gem-crashcourse-daniel-vetter
in acer pc i have /dev/dri/card0

location 509:
in both pc i'm not find info about memory usage in Xorg logs

location 584:
in irbis pc when i start firefox i get some errors and some features not working(for example exit buton and clicks in searching bar)

location 602:
about "startx" it is succesfully starting, but immediately terminating...
i found some information abot xinit(something like a initializaion script, https://bbs.archlinux.org/viewtopic.php?id=168430) more:
https://wiki.archlinux.org/title/xinit
https://wiki.debian.org/Xinitrc

location 809:
in both pc i have empty(filled with 00) snapshot
in https://docs.kernel.org/fb/framebuffer.html same method for make snapshot
fbdev was superseded by DRM (lhttps://en.wikipedia.org/wiki/Direct_Rendering_Infrastructure ) (from here https://en.m.wikipedia.org/wiki/Linux_framebuffer)
drivers read and write to DRM with DMA(Direct memory access) with kernel API https://www.kernel.org/doc/html/v4.16/driver-api/dma-buf.html