This commit lands Phase 5+ of the 3D driver plan. It ports four
ioctl handlers from Linux 7.1 to the Redox DRM scheme and wires
them into the mesa winsys so that the userland/Mesa ↔ kernel/
redox-drm bridge is one ABI step closer to real end-to-end
runtime.
Kernel-side: local/recipes/gpu/redox-drm/source/src/scheme.rs
Four new ioctl numbers (continuing from existing PRIVATE_CS_*):
REDOX_SCANOUT_FLIP = DRM_IOCTL_BASE + 33
REDOX_FENCE_EVENTFD = DRM_IOCTL_BASE + 34
REDOX_CREATE_CONTEXT = DRM_IOCTL_BASE + 35
REDOX_DESTROY_CONTEXT = DRM_IOCTL_BASE + 36
Wire types (Cross-reference with Linux 7.1 source):
RedoxScanoutFlipWire models drivers/gpu/drm/drm_plane.c::
drm_mode_page_flip_ioctl. Page-flip wire
(crtc_id, fb_handle, flags) -> (seqno).
RedoxFenceEventfdWire models drivers/gpu/drm/drm_syncobj.c::
drm_syncobj_wait_ioctl. Fence-eventfd
wire (seqno, timeout_ns). The kernel
watches the CS ring and writes 1 byte
to a userland-supplied eventfd.
RedoxCreateContextWire models drivers/gpu/drm/i915/
i915_gem_context.c. Per-process
context handle (client_handle -> context_id)
so multiple pipe_contexts can submit CS
independently.
Handler functions in the impl block:
handle_scanout_flip() validates fb against active mode and
dispatches to driver.page_flip(). Updates
active_crtc_fb tracking. Pending_flip_fb
bookkeeping mirrors Linux's
drm_mode_page_flip_ioctl behaviour.
handle_fence_eventfd() non-blocking check first (replaces
Phase 4's polling fence); records (seqno,
eventfd) for completion. TODO: real async
via kernel-side epoll (matches drm_syncobj
wait_eventfd).
context_create() allocates a context_id. Per-process CS
state is needed for multi-context iris
+ radeonsi sharing the same winsys.
context_destroy() releases a context_id.
Mesa winsys-side: local/recipes/libs/mesa/source/src/gallium/winsys/redox/
redox_drm_cs.c replaces placeholder ioctl numbers 0x40/0x41
with the real REDOX_PRIVATE_CS_SUBMIT (0xBF)
and REDOX_PRIVATE_CS_WAIT (0xC0) constants,
mirrored from scheme.rs.
redox_drm_fence.c switches from the spin-loop (Phase 4) to
a proper eventfd-backed wait. The fence struct
now has an eventfd field; fence_create()
calls eventfd() and drmIoctl(REDOX_FENCE_EVENTFD).
fence_wait() uses poll(2) on the eventfd. The
eventfd itself is a synthetic stand-in until
the kernel adds epoll to the CS ring (TODO).
redox_drm_surface.c wires the surface_flush path. The TODO
(binding pipe_resource to a framebuffer, then
calling REDOX_SCANOUT_FLIP) is preserved as
the design intent. Mirrors drm_plane.c::
drm_mode_page_flip_ioctl pattern.
redox_drm_winsys.c updates flush_frontbuffer to a stub that
hooks the (screen, resource, surface) triple
for future fb-binding. Multi-context support
is added to the winsys state (next_context_id
+ contexts map).
This is a foundation commit, not a runtime-complete one. The
kernel handlers do basic validation and dispatch; the userland
fence works for the first eventfd wakeup; the surface_flush
waits on the next Phase for pipe_resource→fb_id binding in the
kernel.
Cross-reference: All wire types and handler comments cite
the specific Linux 7.1 source file being ported. Per the AGENTS
rule, these are necessary for cross-reference documentation.
The kernel ABI extension plus winsys update closes Phase 5 of
local/docs/3D-DRIVER-PLAN.md. The remaining work is:
- bind pipe_resource to a framebuffer in the kernel
- real eventfd wakeup (epoll on the CS ring)
- multi-context CS dispatch
- radeonsi SDMA + VM paging (Phase 6+)
- iris full i915 batch buffer path (Phase 6+)
vasilito
9e9edb5cd1