PDCursesMod/fb/drm.c

/* DRM (Direct Rendering Manager,  _not_ Digital Restrictions or Rights
Management!) functions.  Modified from code provided at

https://embear.ch/blog/drm-framebuffer   (describes the code)
https://github.com/embear-engineering/drm-framebuffer   */

#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdint.h>

#include <sys/ioctl.h>
#include <sys/mman.h>

#include <xf86drm.h>
#include <xf86drmMode.h>

struct type_name {
    unsigned int type;
    const char *name;
};

struct framebuffer {
    int fd;
    uint32_t buffer_id;
    uint16_t res_x;
    uint16_t res_y;
    uint8_t *data;
    uint32_t size;
    struct drm_mode_create_dumb dumb_framebuffer;
    drmModeCrtcPtr crtc;
    drmModeConnectorPtr connector;
    drmModeModeInfoPtr resolution;
};

void release_framebuffer(struct framebuffer *fb)
{
    if (fb->fd) {
        /* Try to become master again, else we can't set CRTC. Then the current master needs to reset everything. */
        const int err = drmSetMaster(fb->fd);

//      assert( !err);
        if (fb->crtc) {
            /* Set back to original frame buffer */
            drmModeSetCrtc(fb->fd, fb->crtc->crtc_id, fb->crtc->buffer_id, 0, 0, &fb->connector->connector_id, 1, fb->resolution);
            drmModeFreeCrtc(fb->crtc);
        }
        if (fb->buffer_id)
            drmModeFreeFB(drmModeGetFB(fb->fd, fb->buffer_id));
        /* This will also release resolution */
        if (fb->connector) {
            drmModeFreeConnector(fb->connector);
            fb->resolution = 0;
        }
/*      if (fb->dumb_framebuffer.handle)
            ioctl(fb->fd, DRM_IOCTL_MODE_DESTROY_DUMB, fb->dumb_framebuffer);
*/      if( !err)
            drmDropMaster( fb->fd);
        close(fb->fd);
    }
}

#define FRAMEBUFFER_COULD_NOT_OPEN_DEVICE              -1
#define FRAMEBUFFER_COULD_NOT_GET_RESOURCES            -2
#define FRAMEBUFFER_COULD_NOT_FIND_CONNECTOR           -3
#define FRAMEBUFFER_COULD_NOT_FIND_RESOLUTION          -4
#define FRAMEBUFFER_COULD_NOT_CREATE_FRAMEBUFFER       -5
#define FRAMEBUFFER_COULD_NOT_ADD_FRAMEBUFFER_TO_DRM   -6
#define FRAMEBUFFER_COULD_NOT_GET_ENCODER              -7
#define FRAMEBUFFER_MODE_MAP_FRAMEBUFFER_FAILED        -8
#define FRAMEBUFFER_MODE_MAP_FAILED                    -9

static int n_connectors;

int get_framebuffer(const char *dri_device, const int connector_num, struct framebuffer *fb)
{
    int err;
    int i, fd, j;
    drmModeResPtr res;
    drmModeEncoderPtr encoder = 0;
    drmModeConnectorPtr connector = 0;

    /* Open the dri device /dev/dri/cardX */
    fd = open(dri_device, O_RDWR);
    if (fd < 0)
        return FRAMEBUFFER_COULD_NOT_OPEN_DEVICE;

    /* Get the resources of the DRM device (connectors, encoders, etc.)*/
    res = drmModeGetResources(fd);
    if (!res) {
        close( fd);
        return FRAMEBUFFER_COULD_NOT_GET_RESOURCES;
    }

            /* Count the connectors */
    if( !n_connectors) {
        for( i = 0; i < res->count_connectors; i++) {
            connector = drmModeGetConnectorCurrent(fd, res->connectors[i]);
            if( connector) {
                if( connector->count_modes)
                    n_connectors++;
                drmModeFreeConnector(connector);
            }
        }
    }
    assert( n_connectors);

    /* Search the connector provided as argument */

    for( i = j = 0; i < res->count_connectors; i++) {
        connector = drmModeGetConnectorCurrent(fd, res->connectors[i]);
        if( connector)  {
            if( connector->count_modes) {
                if( j == connector_num % n_connectors)
                    break;
                j++;
            }
            drmModeFreeConnector(connector);
        }
    }
    drmModeFreeResources( res);

    if (!connector)
        return FRAMEBUFFER_COULD_NOT_FIND_CONNECTOR;

    /* Get the preferred resolution */
    drmModeModeInfoPtr resolution = 0;
    for (int i = 0; i < connector->count_modes; i++) {
            resolution = &connector->modes[i];
            if (resolution->type & DRM_MODE_TYPE_PREFERRED)
                    break;
    }

    if (!resolution) {
        err = FRAMEBUFFER_COULD_NOT_FIND_RESOLUTION;
        goto cleanup;
    }

    memset( fb, 0, sizeof( struct framebuffer));
    fb->dumb_framebuffer.height = resolution->vdisplay;
    fb->dumb_framebuffer.width = resolution->hdisplay;
    fb->dumb_framebuffer.bpp = 32;

    err = ioctl(fd, DRM_IOCTL_MODE_CREATE_DUMB, &fb->dumb_framebuffer);
    if (err) {
        err = FRAMEBUFFER_COULD_NOT_CREATE_FRAMEBUFFER;
        goto cleanup;
    }

    err = drmModeAddFB(fd, resolution->hdisplay, resolution->vdisplay, 24, 32,
            fb->dumb_framebuffer.pitch, fb->dumb_framebuffer.handle, &fb->buffer_id);
    if (err) {
        err = FRAMEBUFFER_COULD_NOT_ADD_FRAMEBUFFER_TO_DRM;
        goto cleanup;
    }

    encoder = drmModeGetEncoder(fd, connector->encoder_id);
    if (!encoder) {
        err = FRAMEBUFFER_COULD_NOT_GET_ENCODER;
        goto cleanup;
    }

    /* Get the crtc settings */
    fb->crtc = drmModeGetCrtc(fd, encoder->crtc_id);

    struct drm_mode_map_dumb mreq;

    memset(&mreq, 0, sizeof(mreq));
    mreq.handle = fb->dumb_framebuffer.handle;

    err = drmIoctl(fd, DRM_IOCTL_MODE_MAP_DUMB, &mreq);
    if (err) {
        err = FRAMEBUFFER_MODE_MAP_FRAMEBUFFER_FAILED;
        goto cleanup;
    }

    fb->data = mmap(0, fb->dumb_framebuffer.size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, mreq.offset);
    if (fb->data == MAP_FAILED) {
        err = FRAMEBUFFER_MODE_MAP_FAILED;
        goto cleanup;
    }

    /* Make sure we are not master anymore so that other processes can add new framebuffers as well */
    drmDropMaster(fd);

    fb->fd = fd;
    fb->connector = connector;
    fb->resolution = resolution;

cleanup:
    /* We don't need the encoder and connector anymore so let's free them */
    if (encoder)
        drmModeFreeEncoder(encoder);


    if (err)
        release_framebuffer(fb);

    return err;
}

/* Interface between DRM functions above and PDCursesMod */

static struct framebuffer _drm_framebuffer;
int can_set_master;

static int init_drm( const char *dri_device, const int connector_num)
{
    int err, rval;

    rval = get_framebuffer( dri_device, connector_num, &_drm_framebuffer);
    if( !rval)
    {
        PDC_fb.framebuf = _drm_framebuffer.data;
        PDC_fb.xres     = _drm_framebuffer.dumb_framebuffer.width;
        PDC_fb.yres     = _drm_framebuffer.dumb_framebuffer.height;
        PDC_fb.bits_per_pixel = 32;
        PDC_fb.line_length = _drm_framebuffer.dumb_framebuffer.pitch;
        PDC_fb.smem_len = 0;        /* unused */
        err = drmSetMaster(_drm_framebuffer.fd);
        can_set_master = !err;
        err = drmModeSetCrtc( _drm_framebuffer.fd, _drm_framebuffer.crtc->crtc_id,
                      0, 0, 0, NULL, 0, NULL);
        if( err)
           return( -1);
        assert( !err);
        err = drmModeSetCrtc( _drm_framebuffer.fd, _drm_framebuffer.crtc->crtc_id,
                     _drm_framebuffer.buffer_id, 0, 0,
                     &_drm_framebuffer.connector->connector_id, 1,
                     _drm_framebuffer.resolution);
        if( err)
           drmError( err, "SetCrtc (2)");
        assert( !err);
        if( can_set_master)
           err = drmDropMaster(_drm_framebuffer.fd);
        if( err)
           drmError( err, "DropMaster");
    }
    return( rval);
}

static void close_drm( void)
{
    release_framebuffer( &_drm_framebuffer);
}