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- /*
- * modeset - DRM Modesetting Example
- *
- * Written 2012 by David Rheinsberg <david.rheinsberg@gmail.com>
- * Dedicated to the Public Domain.
- */
- /*
- * DRM Modesetting Howto
- * This document describes the DRM modesetting API. Before we can use the DRM
- * API, we have to include xf86drm.h and xf86drmMode.h. Both are provided by
- * libdrm which every major distribution ships by default. It has no other
- * dependencies and is pretty small.
- *
- * Please ignore all forward-declarations of functions which are used later. I
- * reordered the functions so you can read this document from top to bottom. If
- * you reimplement it, you would probably reorder the functions to avoid all the
- * nasty forward declarations.
- *
- * For easier reading, we ignore all memory-allocation errors of malloc() and
- * friends here. However, we try to correctly handle all other kinds of errors
- * that may occur.
- *
- * All functions and global variables are prefixed with "modeset_*" in this
- * file. So it should be clear whether a function is a local helper or if it is
- * provided by some external library.
- */
- #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>
- struct modeset_dev;
- static int modeset_find_crtc(int fd, drmModeRes *res, drmModeConnector *conn,
- struct modeset_dev *dev);
- static int modeset_create_fb(int fd, struct modeset_dev *dev);
- static int modeset_setup_dev(int fd, drmModeRes *res, drmModeConnector *conn,
- struct modeset_dev *dev);
- static int modeset_open(int *out, const char *node);
- static int modeset_prepare(int fd);
- static void modeset_draw(void);
- static void modeset_cleanup(int fd);
- /*
- * When the linux kernel detects a graphics-card on your machine, it loads the
- * correct device driver (located in kernel-tree at ./drivers/gpu/drm/<xy>) and
- * provides two character-devices to control it. Udev (or whatever hotplugging
- * application you use) will create them as:
- * /dev/dri/card0
- * /dev/dri/controlID64
- * We only need the first one. You can hard-code this path into your application
- * like we do here, but it is recommended to use libudev with real hotplugging
- * and multi-seat support. However, this is beyond the scope of this document.
- * Also note that if you have multiple graphics-cards, there may also be
- * /dev/dri/card1, /dev/dri/card2, ...
- *
- * We simply use /dev/dri/card0 here but the user can specify another path on
- * the command line.
- *
- * modeset_open(out, node): This small helper function opens the DRM device
- * which is given as @node. The new fd is stored in @out on success. On failure,
- * a negative error code is returned.
- * After opening the file, we also check for the DRM_CAP_DUMB_BUFFER capability.
- * If the driver supports this capability, we can create simple memory-mapped
- * buffers without any driver-dependent code. As we want to avoid any radeon,
- * nvidia, intel, etc. specific code, we depend on DUMB_BUFFERs here.
- */
- static int modeset_open(int *out, const char *node)
- {
- int fd, ret;
- uint64_t has_dumb;
- fd = open(node, O_RDWR | O_CLOEXEC);
- if (fd < 0) {
- ret = -errno;
- fprintf(stderr, "cannot open '%s': %m\n", node);
- return ret;
- }
- if (drmGetCap(fd, DRM_CAP_DUMB_BUFFER, &has_dumb) < 0 ||
- !has_dumb) {
- fprintf(stderr, "drm device '%s' does not support dumb buffers\n",
- node);
- close(fd);
- return -EOPNOTSUPP;
- }
- *out = fd;
- return 0;
- }
- /*
- * As a next step we need to find our available display devices. libdrm provides
- * a drmModeRes structure that contains all the needed information. We can
- * retrieve it via drmModeGetResources(fd) and free it via
- * drmModeFreeResources(res) again.
- *
- * A physical connector on your graphics card is called a "connector". You can
- * plug a monitor into it and control what is displayed. We are definitely
- * interested in what connectors are currently used, so we simply iterate
- * through the list of connectors and try to display a test-picture on each
- * available monitor.
- * However, this isn't as easy as it sounds. First, we need to check whether the
- * connector is actually used (a monitor is plugged in and turned on). Then we
- * need to find a CRTC that can control this connector. CRTCs are described
- * later on. After that we create a framebuffer object. If we have all this, we
- * can mmap() the framebuffer and draw a test-picture into it. Then we can tell
- * the DRM device to show the framebuffer on the given CRTC with the selected
- * connector.
- *
- * As we want to draw moving pictures on the framebuffer, we actually have to
- * remember all these settings. Therefore, we create one "struct modeset_dev"
- * object for each connector+crtc+framebuffer pair that we successfully
- * initialized and push it into the global device-list.
- *
- * Each field of this structure is described when it is first used. But as a
- * summary:
- * "struct modeset_dev" contains: {
- * - @next: points to the next device in the single-linked list
- *
- * - @width: width of our buffer object
- * - @height: height of our buffer object
- * - @stride: stride value of our buffer object
- * - @size: size of the memory mapped buffer
- * - @handle: a DRM handle to the buffer object that we can draw into
- * - @map: pointer to the memory mapped buffer
- *
- * - @mode: the display mode that we want to use
- * - @fb: a framebuffer handle with our buffer object as scanout buffer
- * - @conn: the connector ID that we want to use with this buffer
- * - @crtc: the crtc ID that we want to use with this connector
- * - @saved_crtc: the configuration of the crtc before we changed it. We use it
- * so we can restore the same mode when we exit.
- * }
- */
- struct modeset_dev {
- struct modeset_dev *next;
- uint32_t width;
- uint32_t height;
- uint32_t stride;
- uint32_t size;
- uint32_t handle;
- uint8_t *map;
- drmModeModeInfo mode;
- uint32_t fb;
- uint32_t conn;
- uint32_t crtc;
- drmModeCrtc *saved_crtc;
- };
- static struct modeset_dev *modeset_list = NULL;
- /*
- * So as next step we need to actually prepare all connectors that we find. We
- * do this in this little helper function:
- *
- * modeset_prepare(fd): This helper function takes the DRM fd as argument and
- * then simply retrieves the resource-info from the device. It then iterates
- * through all connectors and calls other helper functions to initialize this
- * connector (described later on).
- * If the initialization was successful, we simply add this object as new device
- * into the global modeset device list.
- *
- * The resource-structure contains a list of all connector-IDs. We use the
- * helper function drmModeGetConnector() to retrieve more information on each
- * connector. After we are done with it, we free it again with
- * drmModeFreeConnector().
- * Our helper modeset_setup_dev() returns -ENOENT if the connector is currently
- * unused and no monitor is plugged in. So we can ignore this connector.
- */
- static int modeset_prepare(int fd)
- {
- drmModeRes *res;
- drmModeConnector *conn;
- unsigned int i;
- struct modeset_dev *dev;
- int ret;
- /* 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 a device structure */
- dev = malloc(sizeof(*dev));
- memset(dev, 0, sizeof(*dev));
- dev->conn = conn->connector_id;
- /* call helper function to prepare this connector */
- ret = modeset_setup_dev(fd, res, conn, dev);
- if (ret) {
- if (ret != -ENOENT) {
- errno = -ret;
- fprintf(stderr, "cannot setup device for connector %u:%u (%d): %m\n",
- i, res->connectors[i], errno);
- }
- free(dev);
- drmModeFreeConnector(conn);
- continue;
- }
- /* free connector data and link device into global list */
- drmModeFreeConnector(conn);
- dev->next = modeset_list;
- modeset_list = dev;
- }
- /* free resources again */
- drmModeFreeResources(res);
- return 0;
- }
- /*
- * Now we dig deeper into setting up a single connector. As described earlier,
- * we need to check several things first:
- * * If the connector is currently unused, that is, no monitor is plugged in,
- * then we can ignore it.
- * * We have to find a suitable resolution and refresh-rate. All this is
- * available in drmModeModeInfo structures saved for each crtc. We simply
- * use the first mode that is available. This is always the mode with the
- * highest resolution.
- * A more sophisticated mode-selection should be done in real applications,
- * though.
- * * Then we need to find an CRTC that can drive this connector. A CRTC is an
- * internal resource of each graphics-card. The number of CRTCs controls how
- * many connectors can be controlled indepedently. That is, a graphics-cards
- * may have more connectors than CRTCs, which means, not all monitors can be
- * controlled independently.
- * There is actually the possibility to control multiple connectors via a
- * single CRTC if the monitors should display the same content. However, we
- * do not make use of this here.
- * So think of connectors as pipelines to the connected monitors and the
- * CRTCs are the controllers that manage which data goes to which pipeline.
- * If there are more pipelines than CRTCs, then we cannot control all of
- * them at the same time.
- * * We need to create a framebuffer for this connector. A framebuffer is a
- * memory buffer that we can write XRGB32 data into. So we use this to
- * render our graphics and then the CRTC can scan-out this data from the
- * framebuffer onto the monitor.
- */
- static int modeset_setup_dev(int fd, drmModeRes *res, drmModeConnector *conn,
- struct modeset_dev *dev)
- {
- int ret;
- /* check if a monitor is connected */
- if (conn->connection != DRM_MODE_CONNECTED) {
- fprintf(stderr, "ignoring unused connector %u\n",
- conn->connector_id);
- return -ENOENT;
- }
- /* 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);
- return -EFAULT;
- }
- /* copy the mode information into our device structure */
- memcpy(&dev->mode, &conn->modes[0], sizeof(dev->mode));
- dev->width = conn->modes[0].hdisplay;
- dev->height = conn->modes[0].vdisplay;
- fprintf(stderr, "mode for connector %u is %ux%u\n",
- conn->connector_id, dev->width, dev->height);
- drmMsg("[%s,%d]: connector_id=%d\n",__FUNCTION__,__LINE__, conn->connector_id);
- /* find a crtc for this connector */
- ret = modeset_find_crtc(fd, res, conn, dev);
- if (ret) {
- fprintf(stderr, "no valid crtc for connector %u\n",
- conn->connector_id);
- return ret;
- }
- /* create a framebuffer for this CRTC */
- ret = modeset_create_fb(fd, dev);
- if (ret) {
- fprintf(stderr, "cannot create framebuffer for connector %u\n",
- conn->connector_id);
- return ret;
- }
- return 0;
- }
- /*
- * modeset_find_crtc(fd, res, conn, dev): This small helper tries to find a
- * suitable CRTC for the given connector. We have actually have to introduce one
- * more DRM object to make this more clear: Encoders.
- * Encoders help the CRTC to convert data from a framebuffer into the right
- * format that can be used for the chosen connector. We do not have to
- * understand any more of these conversions to make use of it. However, you must
- * know that each connector has a limited list of encoders that it can use. And
- * each encoder can only work with a limited list of CRTCs. So what we do is
- * trying each encoder that is available and looking for a CRTC that this
- * encoder can work with. If we find the first working combination, we are happy
- * and write it into the @dev structure.
- * But before iterating all available encoders, we first try the currently
- * active encoder+crtc on a connector to avoid a full modeset.
- *
- * However, before we can use a CRTC we must make sure that no other device,
- * that we setup previously, is already using this CRTC. Remember, we can only
- * drive one connector per CRTC! So we simply iterate through the "modeset_list"
- * of previously setup devices and check that this CRTC wasn't used before.
- * Otherwise, we continue with the next CRTC/Encoder combination.
- */
- static int modeset_find_crtc(int fd, drmModeRes *res, drmModeConnector *conn,
- struct modeset_dev *dev)
- {
- drmModeEncoder *enc;
- unsigned int i, j;
- int32_t crtc;
- struct modeset_dev *iter;
- drmMsg("[%s,%d]: connector_id=%d, encoder_id=%d, res->count_crtcs=%d,count_encoders=%d\n",__FUNCTION__,__LINE__,
- conn->connector_id,conn->encoder_id, res->count_crtcs,
- conn->count_encoders);
- /* first try the currently conected encoder+crtc */
- if (conn->encoder_id)
- enc = drmModeGetEncoder(fd, conn->encoder_id);
- else
- enc = NULL;
- if (enc) {
- drmMsg("[%s,%d]: crtc_id=%d\n",__FUNCTION__,__LINE__, enc->crtc_id);
- if (enc->crtc_id) {
- crtc = enc->crtc_id;
- for (iter = modeset_list; iter; iter = iter->next) {
- if (iter->crtc == crtc) {
- crtc = -1;
- break;
- }
- }
- drmMsg("[%s,%d]: crtc=%d\n",__FUNCTION__,__LINE__, crtc);
- if (crtc >= 0) {
- drmModeFreeEncoder(enc);
- dev->crtc = 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 device already uses this CRTC */
- crtc = res->crtcs[j];
- for (iter = modeset_list; iter; iter = iter->next) {
- if (iter->crtc == crtc) {
- crtc = -1;
- break;
- }
- }
- /* we have found a CRTC, so save it and return */
- if (crtc >= 0) {
- drmModeFreeEncoder(enc);
- dev->crtc = crtc;
- return 0;
- }
- }
- drmModeFreeEncoder(enc);
- }
- fprintf(stderr, "cannot find suitable CRTC for connector %u\n",
- conn->connector_id);
- return -ENOENT;
- }
- /*
- * modeset_create_fb(fd, dev): After we have found a crtc+connector+mode
- * combination, we need to actually create a suitable framebuffer that we can
- * use with it. There are actually two ways to do that:
- * * We can create a so called "dumb buffer". This is a buffer that we can
- * memory-map via mmap() and every driver supports this. We can use it for
- * unaccelerated software rendering on the CPU.
- * * We can use libgbm to create buffers available for hardware-acceleration.
- * libgbm is an abstraction layer that creates these buffers for each
- * available DRM driver. As there is no generic API for this, each driver
- * provides its own way to create these buffers.
- * We can then use such buffers to create OpenGL contexts with the mesa3D
- * library.
- * We use the first solution here as it is much simpler and doesn't require any
- * external libraries. However, if you want to use hardware-acceleration via
- * OpenGL, it is actually pretty easy to create such buffers with libgbm and
- * libEGL. But this is beyond the scope of this document.
- *
- * So what we do is requesting a new dumb-buffer from the driver. We specify the
- * same size as the current mode that we selected for the connector.
- * Then we request the driver to prepare this buffer for memory mapping. After
- * that we perform the actual mmap() call. So we can now access the framebuffer
- * memory directly via the dev->map memory map.
- */
- static int modeset_create_fb(int fd, struct modeset_dev *dev)
- {
- struct drm_mode_create_dumb creq;
- struct drm_mode_destroy_dumb dreq;
- struct drm_mode_map_dumb mreq;
- int ret;
- /* create dumb buffer */
- memset(&creq, 0, sizeof(creq));
- creq.width = dev->width;
- creq.height = dev->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;
- }
- dev->stride = creq.pitch;
- dev->size = creq.size;
- dev->handle = creq.handle;
- /* create framebuffer object for the dumb-buffer */
- ret = drmModeAddFB(fd, dev->width, dev->height, 32, 32, dev->stride,
- dev->handle, &dev->fb);
- if (ret) {
- fprintf(stderr, "cannot create framebuffer (%d): %m\n",
- errno);
- ret = -errno;
- goto err_destroy;
- }
- drmMsg("[%s,%d]: dev->fb=%d\n",__FUNCTION__,__LINE__, dev->fb);
- /* prepare buffer for memory mapping */
- memset(&mreq, 0, sizeof(mreq));
- mreq.handle = dev->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 */
- dev->map = mmap(0, dev->size, PROT_READ | PROT_WRITE, MAP_SHARED,
- fd, mreq.offset);
- if (dev->map == MAP_FAILED) {
- fprintf(stderr, "cannot mmap dumb buffer (%d): %m\n",
- errno);
- ret = -errno;
- goto err_fb;
- }
- /* clear the framebuffer to 0 */
- memset(dev->map, 0, dev->size);
- return 0;
- err_fb:
- drmModeRmFB(fd, dev->fb);
- err_destroy:
- memset(&dreq, 0, sizeof(dreq));
- dreq.handle = dev->handle;
- drmIoctl(fd, DRM_IOCTL_MODE_DESTROY_DUMB, &dreq);
- return ret;
- }
- /*
- * Finally! We have a connector with a suitable CRTC. We know which mode we want
- * to use and we have a framebuffer of the correct size that we can write to.
- * There is nothing special left to do. We only have to program the CRTC to
- * connect each new framebuffer to each selected connector for each combination
- * that we saved in the global modeset_list.
- * This is done with a call to drmModeSetCrtc().
- *
- * So we are ready for our main() function. First we check whether the user
- * specified a DRM device on the command line, otherwise we use the default
- * /dev/dri/card0. Then we open the device via modeset_open(). modeset_prepare()
- * prepares all connectors and we can loop over "modeset_list" and call
- * drmModeSetCrtc() on every CRTC/connector combination.
- *
- * But printing empty black pages is boring so we have another helper function
- * modeset_draw() that draws some colors into the framebuffer for 5 seconds and
- * then returns. And then we have all the cleanup functions which correctly free
- * all devices again after we used them. All these functions are described below
- * the main() function.
- *
- * As a side note: drmModeSetCrtc() actually takes a list of connectors that we
- * want to control with this CRTC. We pass only one connector, though. As
- * explained earlier, if we used multiple connectors, then all connectors would
- * have the same controlling framebuffer so the output would be cloned. This is
- * most often not what you want so we avoid explaining this feature here.
- * Furthermore, all connectors will have to run with the same mode, which is
- * also often not guaranteed. So instead, we only use one connector per CRTC.
- *
- * Before calling drmModeSetCrtc() we also save the current CRTC configuration.
- * This is used in modeset_cleanup() to restore the CRTC to the same mode as was
- * before we changed it.
- * If we don't do this, the screen will stay blank after we exit until another
- * application performs modesetting itself.
- */
- int main(int argc, char **argv)
- {
- int ret, fd;
- const char *card;
- struct modeset_dev *iter;
- /* 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;
- /* perform actual modesetting on each found connector+CRTC */
- for (iter = modeset_list; iter; iter = iter->next) {
- drmMsg("[%s,%d]: !!!!!!!!!!!errno=%m. iter->fb=%d \n",__FUNCTION__,__LINE__,iter->fb);
- iter->saved_crtc = drmModeGetCrtc(fd, iter->crtc);
- ret = drmModeSetCrtc(fd, iter->crtc, iter->fb, 0, 0,
- &iter->conn, 1, &iter->mode);
- if (ret) {
- fprintf(stderr, "cannot set CRTC for connector %u (%d): %m\n",
- iter->conn, errno);
- modeset_cleanup(fd);
- }
- }
- /* draw some colors for 5seconds */
- modeset_draw();
- /* 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;
- }
- /*
- * 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;
- }
- /*
- * modeset_draw(): This draws a solid color into all configured framebuffers.
- * Every 100ms the color changes to a slightly different color so we get some
- * kind of smoothly changing color-gradient.
- *
- * The color calculation can be ignored as it is pretty boring. So the
- * interesting stuff is iterating over "modeset_list" and then through all lines
- * and width. We then set each pixel individually to the current color.
- *
- * We do this 50 times as we sleep 100ms after each redraw round. This makes
- * 50*100ms = 5000ms = 5s so it takes about 5seconds to finish this loop.
- *
- * Please note that we draw directly into the framebuffer. This means that you
- * will see flickering as the monitor might refresh while we redraw the screen.
- * To avoid this you would need to use two framebuffers and a call to
- * drmModeSetCrtc() to switch between both buffers.
- * You can also use drmModePageFlip() to do a vsync'ed pageflip. But this is
- * beyond the scope of this document.
- */
- static void modeset_draw(void)
- {
- uint8_t r, g, b;
- bool r_up, g_up, b_up;
- unsigned int i, j, k, off;
- struct modeset_dev *iter;
- srand(time(NULL));
- r = rand() % 0xff;
- g = rand() % 0xff;
- b = rand() % 0xff;
- r_up = g_up = b_up = true;
- for (i = 0; i < 50; ++i) {
- r = next_color(&r_up, r, 20);
- g = next_color(&g_up, g, 10);
- b = next_color(&b_up, b, 5);
- for (iter = modeset_list; iter; iter = iter->next) {
- for (j = 0; j < iter->height; ++j) {
- for (k = 0; k < iter->width; ++k) {
- off = iter->stride * j + k * 4;
- *(uint32_t*)&iter->map[off] =
- (r << 16) | (g << 8) | b;
- }
- }
- }
- usleep(100000);
- }
- }
- /*
- * modeset_cleanup(fd): This cleans up all the devices we created during
- * modeset_prepare(). It resets the CRTCs to their saved states and deallocates
- * all memory.
- * It should be pretty obvious how all of this works.
- */
- static void modeset_cleanup(int fd)
- {
- struct modeset_dev *iter;
- struct drm_mode_destroy_dumb dreq;
- int ret = -1;
- while (modeset_list) {
- /* remove from global list */
- iter = modeset_list;
- modeset_list = iter->next;
- /* restore saved CRTC configuration */
- ret = drmModeSetCrtc(fd,
- iter->saved_crtc->crtc_id,
- iter->saved_crtc->buffer_id,
- iter->saved_crtc->x,
- iter->saved_crtc->y,
- &iter->conn,
- 1,
- &iter->saved_crtc->mode);
- if (ret)
- fprintf(stderr, "cannot set CRTC for connector %u (%d): %m\n",
- iter->conn, errno);
- drmModeFreeCrtc(iter->saved_crtc);
- /* unmap buffer */
- munmap(iter->map, iter->size);
- /* delete framebuffer */
- drmModeRmFB(fd, iter->fb);
- /* delete dumb buffer */
- memset(&dreq, 0, sizeof(dreq));
- dreq.handle = iter->handle;
- drmIoctl(fd, DRM_IOCTL_MODE_DESTROY_DUMB, &dreq);
- /* free allocated memory */
- free(iter);
- }
- }
- /*
- * I hope this was a short but easy overview of the DRM modesetting API. The DRM
- * API offers much more capabilities including:
- * - double-buffering or tripple-buffering (or whatever you want)
- * - vsync'ed page-flips
- * - hardware-accelerated rendering (for example via OpenGL)
- * - output cloning
- * - graphics-clients plus authentication
- * - DRM planes/overlays/sprites
- * - ...
- * If you are interested in these topics, I can currently only redirect you to
- * existing implementations, including:
- * - plymouth (which uses dumb-buffers like this example; very easy to understand)
- * - kmscon (which uses libuterm to do this)
- * - wayland (very sophisticated DRM renderer; hard to understand fully as it
- * uses more complicated techniques like DRM planes)
- * - xserver (very hard to understand as it is split across many files/projects)
- *
- * But understanding how modesetting (as described in this document) works, is
- * essential to understand all further DRM topics.
- *
- * Any feedback is welcome. Feel free to use this code freely for your own
- * documentation or projects.
- *
- * - Hosted on http://github.com/dvdhrm/docs
- * - Written by David Rheinsberg <david.rheinsberg@gmail.com>
- */
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