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- /*
- * modeset-atomic - DRM Atomic-API Modesetting Example
- * Written 2019 by Ezequiel Garcia <ezequiel@collabora.com>
- *
- * Dedicated to the Public Domain.
- */
- /*
- * DRM Double-Buffered VSync'ed Atomic Modesetting Howto
- * This example extends modeset-vsync.c, introducing planes and the
- * atomic API.
- *
- * Planes can be used to blend or overlay images on top of a CRTC
- * framebuffer during the scanout process. Not all hardware provide
- * planes and the number of planes available is also limited. If there's
- * not enough planes available or the hardware does not provide them,
- * users should fallback to composition via GPU or CPU to blend or
- * overlay the planes. Notice that this render process will result
- * in delay, what justifies the usage of planes by modern hardware
- * that needs to be fast.
- *
- * There are three types of planes: primary, cursor and overlay. For
- * compatibility with legacy userspace, the default behavior is to expose
- * only overlay planes to userspace (we're going to see in the code that
- * we have to ask to receive all types of planes). A good example of plane
- * usage is this: imagine a static desktop screen and the user is moving
- * the cursor around. Only the cursor is moving. Instead of calculating the
- * complete scene for each time the user moves its cursor, we can update only
- * the cursor plane and it will be automatically overlayed by the hardware on
- * top of the primary plane. There's no need of software composition in this
- * case.
- *
- * But there was synchronisation problems related to multiple planes
- * usage. The KMS API was not atomic, so you'd have to update the primary
- * plane and then the overlay planes with distinct IOCTL's. This could lead
- * to tearing and also some trouble related to blocking, so the atomic
- * API was proposed to fix these problems.
- *
- * With the introduction of the KMS atomic API, all the planes could get
- * updated in a single IOCTL, using drmModeAtomicCommit(). This can be
- * either asynchronous or fully blocking.
- *
- * This example assumes that you are familiar with modeset-vsync. Only
- * the differences between both files are highlighted here.
- */
- #define _GNU_SOURCE
- #include <errno.h>
- #include <fcntl.h>
- #include <stdbool.h>
- #include <stdint.h>
- #include <stdio.h>
- #include <stdlib.h>
- #include <string.h>
- #include <sys/mman.h>
- #include <time.h>
- #include <unistd.h>
- #include <xf86drm.h>
- #include <xf86drmMode.h>
- #include <drm_fourcc.h>
- /*
- * A new struct is introduced: drm_object. It stores properties of certain
- * objects (connectors, CRTC and planes) that are used in atomic modeset setup
- * and also in atomic page-flips (all planes updated in a single IOCTL).
- */
- struct drm_object {
- drmModeObjectProperties *props;
- drmModePropertyRes **props_info;
- uint32_t id;
- };
- struct modeset_buf {
- uint32_t width;
- uint32_t height;
- uint32_t stride;
- uint32_t size;
- uint32_t handle;
- uint8_t *map;
- uint32_t fb;
- };
- struct modeset_output {
- struct modeset_output *next;
- unsigned int front_buf;
- struct modeset_buf bufs[2];
- struct drm_object connector;
- struct drm_object crtc;
- struct drm_object plane;
- drmModeModeInfo mode;
- uint32_t mode_blob_id;
- uint32_t crtc_index;
- bool pflip_pending;
- bool cleanup;
- uint8_t r, g, b;
- bool r_up, g_up, b_up;
- };
- static struct modeset_output *output_list = NULL;
- /*
- * modeset_open() changes just a little bit. We now have to set that we're going
- * to use the KMS atomic API and check if the device is capable of handling it.
- */
- static int modeset_open(int *out, const char *node)
- {
- int fd, ret;
- uint64_t cap;
- fd = open(node, O_RDWR | O_CLOEXEC);
- if (fd < 0) {
- ret = -errno;
- fprintf(stderr, "cannot open '%s': %m\n", node);
- return ret;
- }
- /* Set that we want to receive all the types of planes in the list. This
- * have to be done since, for legacy reasons, the default behavior is to
- * expose only the overlay planes to the users. The atomic API only
- * works if this is set.
- */
- ret = drmSetClientCap(fd, DRM_CLIENT_CAP_UNIVERSAL_PLANES, 1);
- if (ret) {
- fprintf(stderr, "failed to set universal planes cap, %d\n", ret);
- return ret;
- }
- /* Here we set that we're going to use the KMS atomic API. It's supposed
- * to set the DRM_CLIENT_CAP_UNIVERSAL_PLANES automatically, but it's a
- * safe behavior to set it explicitly as we did in the previous
- * commands. This is also good for learning purposes.
- */
- ret = drmSetClientCap(fd, DRM_CLIENT_CAP_ATOMIC, 1);
- if (ret) {
- fprintf(stderr, "failed to set atomic cap, %d", ret);
- return ret;
- }
- if (drmGetCap(fd, DRM_CAP_DUMB_BUFFER, &cap) < 0 || !cap) {
- fprintf(stderr, "drm device '%s' does not support dumb buffers\n",
- node);
- close(fd);
- return -EOPNOTSUPP;
- }
- if (drmGetCap(fd, DRM_CAP_CRTC_IN_VBLANK_EVENT, &cap) < 0 || !cap) {
- fprintf(stderr, "drm device '%s' does not support atomic KMS\n",
- node);
- close(fd);
- return -EOPNOTSUPP;
- }
- *out = fd;
- return 0;
- }
- /*
- * get_property_value() is a new function. Given a device, the properties of
- * an object and a name, search for the value of property 'name'. If we can't
- * find it, return -1.
- */
- static int64_t get_property_value(int fd, drmModeObjectPropertiesPtr props,
- const char *name)
- {
- drmModePropertyPtr prop;
- uint64_t value;
- bool found;
- int j;
- found = false;
- for (j = 0; j < props->count_props && !found; j++) {
- prop = drmModeGetProperty(fd, props->props[j]);
- if (!strcmp(prop->name, name)) {
- value = props->prop_values[j];
- found = true;
- }
- drmModeFreeProperty(prop);
- }
- if (!found)
- return -1;
- return value;
- }
- /*
- * get_drm_object_properties() is a new helpfer function that retrieves
- * the properties of a certain CRTC, plane or connector object.
- */
- static void modeset_get_object_properties(int fd, struct drm_object *obj,
- uint32_t type)
- {
- const char *type_str;
- unsigned int i;
- obj->props = drmModeObjectGetProperties(fd, obj->id, type);
- if (!obj->props) {
- switch(type) {
- case DRM_MODE_OBJECT_CONNECTOR:
- type_str = "connector";
- break;
- case DRM_MODE_OBJECT_PLANE:
- type_str = "plane";
- break;
- case DRM_MODE_OBJECT_CRTC:
- type_str = "CRTC";
- break;
- default:
- type_str = "unknown type";
- break;
- }
- fprintf(stderr, "cannot get %s %d properties: %s\n",
- type_str, obj->id, strerror(errno));
- return;
- }
- obj->props_info = calloc(obj->props->count_props, sizeof(obj->props_info));
- for (i = 0; i < obj->props->count_props; i++)
- obj->props_info[i] = drmModeGetProperty(fd, obj->props->props[i]);
- }
- /*
- * set_drm_object_property() is a new function. It sets a property value to a
- * CRTC, plane or connector object.
- */
- static int set_drm_object_property(drmModeAtomicReq *req, struct drm_object *obj,
- const char *name, uint64_t value)
- {
- int i;
- uint32_t prop_id = 0;
- for (i = 0; i < obj->props->count_props; i++) {
- if (!strcmp(obj->props_info[i]->name, name)) {
- prop_id = obj->props_info[i]->prop_id;
- break;
- }
- }
- if (prop_id == 0) {
- fprintf(stderr, "no object property: %s\n", name);
- return -EINVAL;
- }
- return drmModeAtomicAddProperty(req, obj->id, prop_id, value);
- }
- /*
- * modeset_find_crtc() changes a little bit. Now we also have to save the CRTC
- * index, and not only its id.
- */
- static int modeset_find_crtc(int fd, drmModeRes *res, drmModeConnector *conn,
- struct modeset_output *out)
- {
- drmModeEncoder *enc;
- unsigned int i, j;
- uint32_t crtc;
- struct modeset_output *iter;
- /* first try the currently conected encoder+crtc */
- if (conn->encoder_id)
- enc = drmModeGetEncoder(fd, conn->encoder_id);
- else
- enc = NULL;
- if (enc) {
- if (enc->crtc_id) {
- crtc = enc->crtc_id;
- for (iter = output_list; iter; iter = iter->next) {
- if (iter->crtc.id == crtc) {
- crtc = 0;
- break;
- }
- }
- if (crtc > 0) {
- drmModeFreeEncoder(enc);
- out->crtc.id = crtc;
- return 0;
- }
- }
- drmModeFreeEncoder(enc);
- }
- /* If the connector is not currently bound to an encoder or if the
- * encoder+crtc is already used by another connector (actually unlikely
- * but lets be safe), iterate all other available encoders to find a
- * matching CRTC.
- */
- for (i = 0; i < conn->count_encoders; ++i) {
- enc = drmModeGetEncoder(fd, conn->encoders[i]);
- if (!enc) {
- fprintf(stderr, "cannot retrieve encoder %u:%u (%d): %m\n",
- i, conn->encoders[i], errno);
- continue;
- }
- /* iterate all global CRTCs */
- for (j = 0; j < res->count_crtcs; ++j) {
- /* check whether this CRTC works with the encoder */
- if (!(enc->possible_crtcs & (1 << j)))
- continue;
- /* check that no other output already uses this CRTC */
- crtc = res->crtcs[j];
- for (iter = output_list; iter; iter = iter->next) {
- if (iter->crtc.id == crtc) {
- crtc = 0;
- break;
- }
- }
- /* We have found a CRTC, so save it and return. Note
- * that we have to save its index as well. The CRTC
- * index (not its ID) will be used when searching for a
- * suitable plane.
- */
- if (crtc > 0) {
- fprintf(stdout, "crtc %u found for encoder %u, will need full modeset\n",
- crtc, conn->encoders[i]);;
- drmModeFreeEncoder(enc);
- out->crtc.id = crtc;
- out->crtc_index = j;
- return 0;
- }
- }
- drmModeFreeEncoder(enc);
- }
- fprintf(stderr, "cannot find suitable crtc for connector %u\n",
- conn->connector_id);
- return -ENOENT;
- }
- /*
- * modeset_find_plane() is a new function. Given a certain combination
- * of connector+CRTC, it looks for a primary plane for it.
- */
- static int modeset_find_plane(int fd, struct modeset_output *out)
- {
- drmModePlaneResPtr plane_res;
- bool found_primary = false;
- int i, ret = -EINVAL;
- plane_res = drmModeGetPlaneResources(fd);
- if (!plane_res) {
- fprintf(stderr, "drmModeGetPlaneResources failed: %s\n",
- strerror(errno));
- return -ENOENT;
- }
- /* iterates through all planes of a certain device */
- for (i = 0; (i < plane_res->count_planes) && !found_primary; i++) {
- int plane_id = plane_res->planes[i];
- drmModePlanePtr plane = drmModeGetPlane(fd, plane_id);
- if (!plane) {
- fprintf(stderr, "drmModeGetPlane(%u) failed: %s\n", plane_id,
- strerror(errno));
- continue;
- }
- /* check if the plane can be used by our CRTC */
- if (plane->possible_crtcs & (1 << out->crtc_index)) {
- drmModeObjectPropertiesPtr props =
- drmModeObjectGetProperties(fd, plane_id, DRM_MODE_OBJECT_PLANE);
- /* Get the "type" property to check if this is a primary
- * plane. Type property is special, as its enum value is
- * defined in UAPI headers. For the properties that are
- * not defined in the UAPI headers, we would have to
- * give kernel the property name and it would return the
- * corresponding enum value. We could also do this for
- * the "type" property, but it would make this simple
- * example more complex. The reason why defining enum
- * values for kernel properties in UAPI headers is
- * deprecated is that string names are easier to both
- * (userspace and kernel) make unique and keep
- * consistent between drivers and kernel versions. But
- * in order to not break userspace, some properties were
- * left in the UAPI headers as well.
- */
- if (get_property_value(fd, props, "type") == DRM_PLANE_TYPE_PRIMARY) {
- found_primary = true;
- out->plane.id = plane_id;
- ret = 0;
- }
- drmModeFreeObjectProperties(props);
- }
- drmModeFreePlane(plane);
- }
- drmModeFreePlaneResources(plane_res);
- if (found_primary)
- fprintf(stdout, "found primary plane, id: %d\n", out->plane.id);
- else
- fprintf(stdout, "couldn't find a primary plane\n");
- return ret;
- }
- /*
- * modeset_drm_object_fini() is a new helper function that destroys CRTCs,
- * connectors and planes
- */
- static void modeset_drm_object_fini(struct drm_object *obj)
- {
- for (int i = 0; i < obj->props->count_props; i++)
- drmModeFreeProperty(obj->props_info[i]);
- free(obj->props_info);
- drmModeFreeObjectProperties(obj->props);
- }
- /*
- * modeset_setup_objects() is a new function. It helps us to retrieve
- * connector, CRTC and plane objects properties from the device. These
- * properties will help us during the atomic modesetting commit, so we save
- * them in our struct modeset_output object.
- */
- static int modeset_setup_objects(int fd, struct modeset_output *out)
- {
- struct drm_object *connector = &out->connector;
- struct drm_object *crtc = &out->crtc;
- struct drm_object *plane = &out->plane;
- /* retrieve connector properties from the device */
- modeset_get_object_properties(fd, connector, DRM_MODE_OBJECT_CONNECTOR);
- if (!connector->props)
- goto out_conn;
- /* retrieve CRTC properties from the device */
- modeset_get_object_properties(fd, crtc, DRM_MODE_OBJECT_CRTC);
- if (!crtc->props)
- goto out_crtc;
- /* retrieve plane properties from the device */
- modeset_get_object_properties(fd, plane, DRM_MODE_OBJECT_PLANE);
- if (!plane->props)
- goto out_plane;
- return 0;
- out_plane:
- modeset_drm_object_fini(crtc);
- out_crtc:
- modeset_drm_object_fini(connector);
- out_conn:
- return -ENOMEM;
- }
- /*
- * modeset_destroy_objects() is a new function. It destroys what we allocate
- * in modeset_setup_objects().
- */
- static void modeset_destroy_objects(int fd, struct modeset_output *out)
- {
- modeset_drm_object_fini(&out->connector);
- modeset_drm_object_fini(&out->crtc);
- modeset_drm_object_fini(&out->plane);
- }
- /*
- * modeset_create_fb() stays the same.
- */
- static int modeset_create_fb(int fd, struct modeset_buf *buf)
- {
- struct drm_mode_create_dumb creq;
- struct drm_mode_destroy_dumb dreq;
- struct drm_mode_map_dumb mreq;
- int ret;
- uint32_t handles[4] = {0}, pitches[4] = {0}, offsets[4] = {0};
- /* create dumb buffer */
- memset(&creq, 0, sizeof(creq));
- creq.width = buf->width;
- creq.height = buf->height;
- creq.bpp = 32;
- ret = drmIoctl(fd, DRM_IOCTL_MODE_CREATE_DUMB, &creq);
- if (ret < 0) {
- fprintf(stderr, "cannot create dumb buffer (%d): %m\n",
- errno);
- return -errno;
- }
- buf->stride = creq.pitch;
- buf->size = creq.size;
- buf->handle = creq.handle;
- /* create framebuffer object for the dumb-buffer */
- handles[0] = buf->handle;
- pitches[0] = buf->stride;
- ret = drmModeAddFB2(fd, buf->width, buf->height, DRM_FORMAT_RGB565,
- handles, pitches, offsets, &buf->fb, 0);
- if (ret) {
- fprintf(stderr, "cannot create framebuffer (%d): %m\n",
- errno);
- ret = -errno;
- goto err_destroy;
- }
- /* prepare buffer for memory mapping */
- memset(&mreq, 0, sizeof(mreq));
- mreq.handle = buf->handle;
- ret = drmIoctl(fd, DRM_IOCTL_MODE_MAP_DUMB, &mreq);
- if (ret) {
- fprintf(stderr, "cannot map dumb buffer (%d): %m\n",
- errno);
- ret = -errno;
- goto err_fb;
- }
- /* perform actual memory mapping */
- buf->map = mmap(0, buf->size, PROT_READ | PROT_WRITE, MAP_SHARED,
- fd, mreq.offset);
- if (buf->map == MAP_FAILED) {
- fprintf(stderr, "cannot mmap dumb buffer (%d): %m\n",
- errno);
- ret = -errno;
- goto err_fb;
- }
- /* clear the framebuffer to 0 */
- memset(buf->map, 0, buf->size);
- return 0;
- err_fb:
- drmModeRmFB(fd, buf->fb);
- err_destroy:
- memset(&dreq, 0, sizeof(dreq));
- dreq.handle = buf->handle;
- drmIoctl(fd, DRM_IOCTL_MODE_DESTROY_DUMB, &dreq);
- return ret;
- }
- /*
- * modeset_destroy_fb() stays the same.
- */
- static void modeset_destroy_fb(int fd, struct modeset_buf *buf)
- {
- struct drm_mode_destroy_dumb dreq;
- /* unmap buffer */
- munmap(buf->map, buf->size);
- /* delete framebuffer */
- drmModeRmFB(fd, buf->fb);
- /* delete dumb buffer */
- memset(&dreq, 0, sizeof(dreq));
- dreq.handle = buf->handle;
- drmIoctl(fd, DRM_IOCTL_MODE_DESTROY_DUMB, &dreq);
- }
- /*
- * modeset_setup_framebuffers() creates framebuffers for the back and front
- * buffers of a certain output. Also, it copies the connector mode to these
- * buffers.
- */
- static int modeset_setup_framebuffers(int fd, drmModeConnector *conn,
- struct modeset_output *out)
- {
- int i, ret;
- /* setup the front and back framebuffers */
- for (i = 0; i < 2; i++) {
- /* copy mode info to buffer */
- out->bufs[i].width = conn->modes[0].hdisplay;
- out->bufs[i].height = conn->modes[0].vdisplay;
- /* create a framebuffer for the buffer */
- ret = modeset_create_fb(fd, &out->bufs[i]);
- if (ret) {
- /* the second framebuffer creation failed, so
- * we have to destroy the first before returning */
- if (i == 1)
- modeset_destroy_fb(fd, &out->bufs[0]);
- return ret;
- }
- }
- return 0;
- }
- /*
- * modeset_output_destroy() is new. It destroys the objects (connector, crtc and
- * plane), front and back buffers, the mode blob property and then destroys the
- * output itself.
- */
- static void modeset_output_destroy(int fd, struct modeset_output *out)
- {
- /* destroy connector, crtc and plane objects */
- modeset_destroy_objects(fd, out);
- /* destroy front/back framebuffers */
- modeset_destroy_fb(fd, &out->bufs[0]);
- modeset_destroy_fb(fd, &out->bufs[1]);
- /* destroy mode blob property */
- drmModeDestroyPropertyBlob(fd, out->mode_blob_id);
- free(out);
- }
- /*
- * With a certain combination of connector+CRTC, we look for a suitable primary
- * plane for it. After that, we retrieve connector, CRTC and plane objects
- * properties from the device. These objects are used during the atomic modeset
- * setup (see modeset_atomic_prepare_commit()) and also during the page-flips
- * (see modeset_draw_out() and modeset_atomic_commit()).
- *
- * Besides that, we have to create a blob property that receives the output
- * mode. When we perform an atomic commit, the driver expects a CRTC property
- * named "MODE_ID", which points to the id of a blob. This usually happens for
- * properties that are not simple types. In this particular case, out->mode is a
- * struct. But we could have another property that expects the id of a blob that
- * holds an array, for instance.
- */
- static struct modeset_output *modeset_output_create(int fd, drmModeRes *res,
- drmModeConnector *conn)
- {
- int ret;
- struct modeset_output *out;
- /* creates an output structure */
- out = malloc(sizeof(*out));
- memset(out, 0, sizeof(*out));
- out->connector.id = conn->connector_id;
- /* check if a monitor is connected */
- if (conn->connection != DRM_MODE_CONNECTED) {
- fprintf(stderr, "ignoring unused connector %u\n",
- conn->connector_id);
- goto out_error;
- }
- /* check if there is at least one valid mode */
- if (conn->count_modes == 0) {
- fprintf(stderr, "no valid mode for connector %u\n",
- conn->connector_id);
- goto out_error;
- }
- /* copy the mode information into our output structure */
- memcpy(&out->mode, &conn->modes[0], sizeof(out->mode));
- /* create the blob property using out->mode and save its id in the output*/
- if (drmModeCreatePropertyBlob(fd, &out->mode, sizeof(out->mode),
- &out->mode_blob_id) != 0) {
- fprintf(stderr, "couldn't create a blob property\n");
- goto out_error;
- }
- fprintf(stderr, "mode for connector %u is %ux%u\n",
- conn->connector_id, out->bufs[0].width, out->bufs[0].height);
- /* find a crtc for this connector */
- ret = modeset_find_crtc(fd, res, conn, out);
- if (ret) {
- fprintf(stderr, "no valid crtc for connector %u\n",
- conn->connector_id);
- goto out_blob;
- }
- /* with a connector and crtc, find a primary plane */
- ret = modeset_find_plane(fd, out);
- if (ret) {
- fprintf(stderr, "no valid plane for crtc %u\n", out->crtc.id);
- goto out_blob;
- }
- /* gather properties of our connector, CRTC and planes */
- ret = modeset_setup_objects(fd, out);
- if (ret) {
- fprintf(stderr, "cannot get plane properties\n");
- goto out_blob;
- }
- /* setup front/back framebuffers for this CRTC */
- ret = modeset_setup_framebuffers(fd, conn, out);
- if (ret) {
- fprintf(stderr, "cannot create framebuffers for connector %u\n",
- conn->connector_id);
- goto out_obj;
- }
- return out;
- out_obj:
- modeset_destroy_objects(fd, out);
- out_blob:
- drmModeDestroyPropertyBlob(fd, out->mode_blob_id);
- out_error:
- free(out);
- return NULL;
- }
- /*
- * modeset_prepare() changes a little bit. Now we use the new function
- * modeset_output_create() to allocate memory and setup the output.
- */
- static int modeset_prepare(int fd)
- {
- drmModeRes *res;
- drmModeConnector *conn;
- unsigned int i;
- struct modeset_output *out;
- /* retrieve resources */
- res = drmModeGetResources(fd);
- if (!res) {
- fprintf(stderr, "cannot retrieve DRM resources (%d): %m\n",
- errno);
- return -errno;
- }
- /* iterate all connectors */
- for (i = 0; i < res->count_connectors; ++i) {
- /* get information for each connector */
- conn = drmModeGetConnector(fd, res->connectors[i]);
- if (!conn) {
- fprintf(stderr, "cannot retrieve DRM connector %u:%u (%d): %m\n",
- i, res->connectors[i], errno);
- continue;
- }
- /* create an output structure and free connector data */
- out = modeset_output_create(fd, res, conn);
- drmModeFreeConnector(conn);
- if (!out)
- continue;
- /* link output into global list */
- out->next = output_list;
- output_list = out;
- }
- if (!output_list) {
- fprintf(stderr, "couldn't create any outputs\n");
- return -1;
- }
- /* free resources again */
- drmModeFreeResources(res);
- return 0;
- }
- /*
- * modeset_atomic_prepare_commit() is new. Here we set the values of properties
- * (of our connector, CRTC and plane objects) that we want to change in the
- * atomic commit. These changes are temporarily stored in drmModeAtomicReq *req
- * until the commit actually happens.
- */
- static int modeset_atomic_prepare_commit(int fd, struct modeset_output *out,
- drmModeAtomicReq *req)
- {
- struct drm_object *plane = &out->plane;
- struct modeset_buf *buf = &out->bufs[out->front_buf ^ 1];
- /* set id of the CRTC id that the connector is using */
- if (set_drm_object_property(req, &out->connector, "CRTC_ID", out->crtc.id) < 0)
- return -1;
- /* set the mode id of the CRTC; this property receives the id of a blob
- * property that holds the struct that actually contains the mode info */
- if (set_drm_object_property(req, &out->crtc, "MODE_ID", out->mode_blob_id) < 0)
- return -1;
- /* set the CRTC object as active */
- if (set_drm_object_property(req, &out->crtc, "ACTIVE", 1) < 0)
- return -1;
- /* set properties of the plane related to the CRTC and the framebuffer */
- if (set_drm_object_property(req, plane, "FB_ID", buf->fb) < 0)
- return -1;
- if (set_drm_object_property(req, plane, "CRTC_ID", out->crtc.id) < 0)
- return -1;
- if (set_drm_object_property(req, plane, "SRC_X", 0) < 0)
- return -1;
- if (set_drm_object_property(req, plane, "SRC_Y", 0) < 0)
- return -1;
- if (set_drm_object_property(req, plane, "SRC_W", buf->width << 16) < 0)
- return -1;
- if (set_drm_object_property(req, plane, "SRC_H", buf->height << 16) < 0)
- return -1;
- if (set_drm_object_property(req, plane, "CRTC_X", 0) < 0)
- return -1;
- if (set_drm_object_property(req, plane, "CRTC_Y", 0) < 0)
- return -1;
- if (set_drm_object_property(req, plane, "CRTC_W", buf->width) < 0)
- return -1;
- if (set_drm_object_property(req, plane, "CRTC_H", buf->height) < 0)
- return -1;
- return 0;
- }
- /*
- * A short helper function to compute a changing color value. No need to
- * understand it.
- */
- static uint8_t next_color(bool *up, uint8_t cur, unsigned int mod)
- {
- uint8_t next;
- next = cur + (*up ? 1 : -1) * (rand() % mod);
- if ((*up && next < cur) || (!*up && next > cur)) {
- *up = !*up;
- next = cur;
- }
- return next;
- }
- /*
- * Draw on back framebuffer before the page-flip is requested.
- */
- static void modeset_paint_framebuffer(struct modeset_output *out)
- {
- struct modeset_buf *buf;
- unsigned int j, k, off;
- /* draw on back framebuffer */
- out->r = next_color(&out->r_up, out->r, 5);
- out->g = next_color(&out->g_up, out->g, 5);
- out->b = next_color(&out->b_up, out->b, 5);
- buf = &out->bufs[out->front_buf ^ 1];
- for (j = 0; j < buf->height; ++j) {
- for (k = 0; k < buf->width; ++k) {
- off = buf->stride * j + k * 4;
- *(uint32_t*)&buf->map[off] =
- (out->r << 16) | (out->g << 8) | out->b;
- }
- }
- }
- /*
- * modeset_draw_out() prepares the framebuffer with the drawing and then it asks
- * for the driver to perform an atomic commit. This will lead to a page-flip and
- * the content of the framebuffer will be displayed. In this simple example
- * we're only using the primary plane, but we could also be updating other
- * planes in the same atomic commit.
- *
- * Just like in modeset_perform_modeset(), we first setup everything with
- * modeset_atomic_prepare_commit() and then actually perform the atomic commit.
- * But there are some important differences:
- *
- * 1. Here we just want to perform a commit that changes the state of a specific
- * output, and in modeset_perform_modeset() we did an atomic commit that was
- * supposed to setup all the outputs at once. So there's no need to prepare
- * every output before performing the atomic commit. But let's suppose you
- * prepare every output and then perform the commit. It should schedule a
- * page-flip for all of them, but modeset_draw_out() was called because the
- * page-flip for a specific output has finished. The others may not be
- * prepared for a page-flip yet (e.g. in the middle of a scanout), so these
- * page-flips will fail.
- *
- * 2. Here we have already painted the framebuffer and also we don't use the
- * flag DRM_MODE_ALLOW_MODESET anymore, since the modeset already happened.
- * We could continue to use this flag, as it makes no difference if
- * modeset_perform_modeset() is correct and there's no bug in the kernel.
- * The flag only allows (it doesn't force) the driver to perform a modeset,
- * but we have already performed it in modeset_perform_modeset() and now we
- * just want page-flips to occur. If we still need to perform modesets it
- * means that we have a bug somewhere, and it may be better to fail than to
- * glitch (a modeset can cause unecessary latency and also blank the screen).
- */
- static void modeset_draw_out(int fd, struct modeset_output *out)
- {
- drmModeAtomicReq *req;
- int ret, flags;
- /* draw on framebuffer of the output */
- modeset_paint_framebuffer(out);
- /* prepare output for atomic commit */
- req = drmModeAtomicAlloc();
- ret = modeset_atomic_prepare_commit(fd, out, req);
- if (ret < 0) {
- fprintf(stderr, "prepare atomic commit failed, %d\n", errno);
- return;
- }
- /* We've just draw on the framebuffer, prepared the commit and now it's
- * time to perform a page-flip to display its content.
- *
- * DRM_MODE_PAGE_FLIP_EVENT signalizes that we want to receive a
- * page-flip event in the DRM-fd when the page-flip happens. This flag
- * is also used in the non-atomic examples, so you're probably familiar
- * with it.
- *
- * DRM_MODE_ATOMIC_NONBLOCK makes the page-flip non-blocking. We don't
- * want to be blocked waiting for the commit to happen, since we can use
- * this time to prepare a new framebuffer, for instance. We can only do
- * this because there are mechanisms to know when the commit is complete
- * (like page flip event, explained above).
- */
- flags = DRM_MODE_PAGE_FLIP_EVENT | DRM_MODE_ATOMIC_NONBLOCK;
- ret = drmModeAtomicCommit(fd, req, flags, NULL);
- drmModeAtomicFree(req);
- if (ret < 0) {
- fprintf(stderr, "atomic commit failed, %d\n", errno);
- return;
- }
- out->front_buf ^= 1;
- out->pflip_pending = true;
- }
- /*
- * modeset_page_flip_event() changes. Now that we are using page_flip_handler2,
- * we also receive the CRTC that is responsible for this event. When using the
- * atomic API we commit multiple CRTC's at once, so we need the information of
- * what output caused the event in order to schedule a new page-flip for it.
- */
- static void modeset_page_flip_event(int fd, unsigned int frame,
- unsigned int sec, unsigned int usec,
- unsigned int crtc_id, void *data)
- {
- struct modeset_output *out, *iter;
- /* find the output responsible for this event */
- out = NULL;
- for (iter = output_list; iter; iter = iter->next) {
- if (iter->crtc.id == crtc_id) {
- out = iter;
- break;
- }
- }
- if (out == NULL)
- return;
- out->pflip_pending = false;
- if (!out->cleanup)
- modeset_draw_out(fd, out);
- }
- /*
- * modeset_perform_modeset() is new. First we define what properties have to be
- * changed and the values that they will receive. To check if the modeset will
- * work as expected, we perform an atomic commit with the flag
- * DRM_MODE_ATOMIC_TEST_ONLY. With this flag the DRM driver tests if the atomic
- * commit would work, but it doesn't commit it to the hardware. After, the same
- * atomic commit is performed without the TEST_ONLY flag, but not only before we
- * draw on the framebuffers of the outputs. This is necessary to avoid
- * displaying unwanted content.
- *
- * NOTE: we can't perform an atomic commit without an attached frambeuffer
- * (even when we have DRM_MODE_ATOMIC_TEST_ONLY). It will simply fail.
- */
- static int modeset_perform_modeset(int fd)
- {
- int ret, flags;
- struct modeset_output *iter;
- drmModeAtomicReq *req;
- /* prepare modeset on all outputs */
- req = drmModeAtomicAlloc();
- for (iter = output_list; iter; iter = iter->next) {
- ret = modeset_atomic_prepare_commit(fd, iter, req);
- if (ret < 0)
- break;
- }
- if (ret < 0) {
- fprintf(stderr, "prepare atomic commit failed, %d\n", errno);
- return ret;
- }
- /* perform test-only atomic commit */
- flags = DRM_MODE_ATOMIC_TEST_ONLY | DRM_MODE_ATOMIC_ALLOW_MODESET;
- ret = drmModeAtomicCommit(fd, req, flags, NULL);
- if (ret < 0) {
- fprintf(stderr, "test-only atomic commit failed, %d\n", errno);
- drmModeAtomicFree(req);
- return ret;
- }
- /* draw on back framebuffer of all outputs */
- for (iter = output_list; iter; iter = iter->next) {
- /* colors initialization, this is the first time we're drawing */
- iter->r = rand() % 0xff;
- iter->g = rand() % 0xff;
- iter->b = rand() % 0xff;
- iter->r_up = iter->g_up = iter->b_up = true;
- modeset_paint_framebuffer(iter);
- }
- /* initial modeset on all outputs */
- flags = DRM_MODE_ATOMIC_ALLOW_MODESET | DRM_MODE_PAGE_FLIP_EVENT;
- ret = drmModeAtomicCommit(fd, req, flags, NULL);
- if (ret < 0)
- fprintf(stderr, "modeset atomic commit failed, %d\n", errno);
- drmModeAtomicFree(req);
- return ret;
- }
- /*
- * modeset_draw() changes. If we got here, the modeset already occurred. When
- * the page-flip for a certain output is done, an event will be fired and we'll
- * be able to handle it.
- *
- * Here we define the function that should handle these events, which is
- * modeset_page_flip_event(). This function calls modeset_draw_out(), which is
- * responsible for preparing a new framebuffer and performing another atomic
- * commit for us.
- *
- * Then we have a 5 seconds loop that keeps waiting for the events that are
- * fired when the page-flip is complete. drmHandleEvent() is reponsible for
- * reading the events from the fd and to call modeset_page_flip_event() for
- * each one of them.
- */
- static void modeset_draw(int fd)
- {
- int ret;
- fd_set fds;
- time_t start, cur;
- struct timeval v;
- drmEventContext ev;
- /* init variables */
- srand(time(&start));
- FD_ZERO(&fds);
- memset(&v, 0, sizeof(v));
- memset(&ev, 0, sizeof(ev));
- /* 3 is the first version that allow us to use page_flip_handler2, which
- * is just like page_flip_handler but with the addition of passing the
- * crtc_id as argument to the function that will handle page-flip events
- * (in our case, modeset_page_flip_event()). This is good because we can
- * find out for what output the page-flip happened.
- *
- * The usage of page_flip_handler2 is the reason why we needed to verify
- * the support for DRM_CAP_CRTC_IN_VBLANK_EVENT.
- */
- ev.version = 3;
- ev.page_flip_handler2 = modeset_page_flip_event;
- /* perform modeset using atomic commit */
- modeset_perform_modeset(fd);
- /* wait 5s for VBLANK or input events */
- while (time(&cur) < start + 5) {
- FD_SET(0, &fds);
- FD_SET(fd, &fds);
- v.tv_sec = start + 5 - cur;
- ret = select(fd + 1, &fds, NULL, NULL, &v);
- if (ret < 0) {
- fprintf(stderr, "select() failed with %d: %m\n", errno);
- break;
- } else if (FD_ISSET(0, &fds)) {
- fprintf(stderr, "exit due to user-input\n");
- break;
- } else if (FD_ISSET(fd, &fds)) {
- /* read the fd looking for events and handle each event
- * by calling modeset_page_flip_event() */
- drmHandleEvent(fd, &ev);
- }
- }
- }
- /*
- * modeset_cleanup() stays the same.
- */
- static void modeset_cleanup(int fd)
- {
- struct modeset_output *iter;
- drmEventContext ev;
- int ret;
- /* init variables */
- memset(&ev, 0, sizeof(ev));
- ev.version = 3;
- ev.page_flip_handler2 = modeset_page_flip_event;
- while (output_list) {
- /* get first output from list */
- iter = output_list;
- /* if a page-flip is pending, wait for it to complete */
- iter->cleanup = true;
- fprintf(stderr, "wait for pending page-flip to complete...\n");
- while (iter->pflip_pending) {
- ret = drmHandleEvent(fd, &ev);
- if (ret)
- break;
- }
- /* move head of the list to the next output */
- output_list = iter->next;
- /* destroy current output */
- modeset_output_destroy(fd, iter);
- }
- }
- /*
- * main() also changes. Instead of performing the KMS setup calling
- * drmModeSetCrtc(), we instead setup it using the atomic API with the
- * function modeset_perform_modeset(), which is called by modeset_draw().
- */
- int main(int argc, char **argv)
- {
- int ret, fd;
- const char *card;
- /* check which DRM device to open */
- if (argc > 1)
- card = argv[1];
- else
- card = "/dev/dri/card0";
- fprintf(stderr, "using card '%s'\n", card);
- /* open the DRM device */
- ret = modeset_open(&fd, card);
- if (ret)
- goto out_return;
- /* prepare all connectors and CRTCs */
- ret = modeset_prepare(fd);
- if (ret)
- goto out_close;
- /* draw some colors for 5seconds */
- modeset_draw(fd);
- /* cleanup everything */
- modeset_cleanup(fd);
- ret = 0;
- out_close:
- close(fd);
- out_return:
- if (ret) {
- errno = -ret;
- fprintf(stderr, "modeset failed with error %d: %m\n", errno);
- } else {
- fprintf(stderr, "exiting\n");
- }
- return ret;
- }
- /*
- * This is a very simple example to show how to use the KMS atomic API and how
- * different it is from legacy KMS. Most modern drivers are using the atomic
- * API, so it is important to have this example.
- *
- * Just like vsync'ed double-buffering, the atomic API does not not solve all
- * the problems that can happen and you have to figure out the best
- * implementation for your use case.
- *
- * If you want to take a look at more complex examples that makes use of KMS
- * atomic API, I can recommend you:
- *
- * - kms-quads: https://gitlab.freedesktop.org/daniels/kms-quads/
- * A more complex (but also well-explained) example that can be used to
- * learn how to build a compositor using the atomic API. Supports both
- * GL and software rendering.
- *
- * - Weston: https://gitlab.freedesktop.org/wayland/weston
- * Reference implementation of a Wayland compositor. It's a very
- * sophisticated DRM renderer, hard to understand fully as it uses more
- * complicated techniques like DRM planes.
- *
- * Any feedback is welcome. Feel free to use this code freely for your own
- * documentation or projects.
- *
- * - Hosted on http://github.com/dvdhrm/docs
- */
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