b411836478
Alpine's libinput, libseat, seatd, xf86-input-libinput and usbutils join the image, and seatd runs from schinit. libinput lists the keyboard and pointer as an ordinary user, Xorg now drives both through libinput, and a program linked to libseat running as schos opens seat0 through seatd, is handed /dev/input/event0 and reads its name through the descriptor. Two kernel bugs stood in the way, and both would have stopped a Wayland compositor too. The socket connect() queues for a listener was allocated with its domain at zero, so sendmsg refused SCM_RIGHTS on the accepted end: a server could receive descriptors and never send one. And sendmsg treated a control buffer longer than its messages as an error, where Linux takes a following header too short to be one as the end; seatd passes a zeroed CMSG_SPACE array with one descriptor at the front. Found with /proc/strace and a temporary kinfo in sendmsg's EINVAL sites. Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01EVRhxi9zpdW2uDUN4FVcao
17 lines
586 B
Text
17 lines
586 B
Text
# The seat daemon: hands a Wayland compositor (through libseat) the input and
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# display devices it needs without running the compositor as root. seatd opens
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# them as itself and passes the file descriptors over its socket; the socket is
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# group `video`, which the first user is in.
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#
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# Alpine's seatd package. A compositor that runs as root, or one started with
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# seatd-launch, needs none of this.
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Label = os.schos.seatd
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Program = /usr/bin/seatd
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Args = seatd -g video
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RunAtLoad = yes
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KeepAlive = yes
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ThrottleInterval = 3
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StandardOut = /dev/null
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StandardError = /dev/null
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