The BO handle table exists to avoid double-closing a BO handle, which aren't reference-counted by the kernel. But if we can guarantee that there is only ever a single ref for each BO handle, then we don't need the BO handle table anymore. This is possible if we create the handle right before the ADDFB2 IOCTL, and close the handle right after. The handles are very short-lived and we don't need to track their lifetime. Because of multi-planar FBs, we need to be a bit careful: some FB planes might share the same handle. But with a small check, it's easy to avoid double-closing the same handle (which wouldn't be a big deal anyways). There's one gotcha though: drmModeSetCursor2 takes a BO handle as input. Saving the handles until drmModeSetCursor2 time would require us to track BO handle lifetimes, so we wouldn't be able to get rid of the BO handle table. As a workaround, use drmModeGetFB to turn the FB ID back to a BO handle, call drmModeSetCursor2 and then immediately close the BO handle. The overhead should be minimal since these IOCTLs are pretty cheap. Closes: https://github.com/swaywm/wlroots/issues/3164master
Simon Ser
3 years ago
parent
3b96aa04db
commit
0817c52a21
@ -1,43 +0,0 @@
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#include <assert.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <wlr/util/log.h>
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#include "backend/drm/bo_handle_table.h"
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static size_t align(size_t val, size_t align) {
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size_t mask = align - 1;
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return (val + mask) & ~mask;
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}
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void drm_bo_handle_table_finish(struct wlr_drm_bo_handle_table *table) {
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free(table->nrefs);
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}
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bool drm_bo_handle_table_ref(struct wlr_drm_bo_handle_table *table,
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uint32_t handle) {
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assert(handle != 0);
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if (handle > table->len) {
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// Grow linearly, because we don't expect the number of BOs to explode
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size_t len = align(handle + 1, 512);
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size_t *nrefs = realloc(table->nrefs, len * sizeof(size_t));
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if (nrefs == NULL) {
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wlr_log_errno(WLR_ERROR, "realloc failed");
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return false;
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}
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memset(&nrefs[table->len], 0, (len - table->len) * sizeof(size_t));
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table->len = len;
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table->nrefs = nrefs;
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}
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table->nrefs[handle]++;
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return true;
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}
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size_t drm_bo_handle_table_unref(struct wlr_drm_bo_handle_table *table,
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uint32_t handle) {
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assert(handle < table->len);
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assert(table->nrefs[handle] > 0);
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table->nrefs[handle]--;
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return table->nrefs[handle];
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}
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@ -1,24 +0,0 @@
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#ifndef BACKEND_DRM_BO_HANDLE_TABLE_H
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#define BACKEND_DRM_BO_HANDLE_TABLE_H
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/**
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* Table performing reference counting for buffer object handles.
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*
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* The BO handles are allocated incrementally and are recycled by the kernel,
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* so a simple array is used.
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*
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* This design is inspired from amdgpu's code in libdrm:
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* https://gitlab.freedesktop.org/mesa/drm/-/blob/1a4c0ec9aea13211997f982715fe5ffcf19dd067/amdgpu/handle_table.c
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*/
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struct wlr_drm_bo_handle_table {
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size_t *nrefs;
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size_t len;
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};
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void drm_bo_handle_table_finish(struct wlr_drm_bo_handle_table *table);
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bool drm_bo_handle_table_ref(struct wlr_drm_bo_handle_table *table,
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uint32_t handle);
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size_t drm_bo_handle_table_unref(struct wlr_drm_bo_handle_table *table,
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uint32_t handle);
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#endif
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