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diff --git a/minui/graphics_fbdev.cpp b/minui/graphics_fbdev.cpp
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+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <fcntl.h>
+#include <stdio.h>
+
+#include <sys/cdefs.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <sys/types.h>
+
+#include <linux/fb.h>
+#include <linux/kd.h>
+
+#include "minui.h"
+#include "graphics.h"
+
+static gr_surface fbdev_init(minui_backend*);
+static gr_surface fbdev_flip(minui_backend*);
+static void fbdev_blank(minui_backend*, bool);
+static void fbdev_exit(minui_backend*);
+
+static GRSurface gr_framebuffer[2];
+static bool double_buffered;
+static GRSurface* gr_draw = NULL;
+static int displayed_buffer;
+
+static fb_var_screeninfo vi;
+static int fb_fd = -1;
+
+static minui_backend my_backend = {
+ .init = fbdev_init,
+ .flip = fbdev_flip,
+ .blank = fbdev_blank,
+ .exit = fbdev_exit,
+};
+
+minui_backend* open_fbdev() {
+ return &my_backend;
+}
+
+static void fbdev_blank(minui_backend* backend __unused, bool blank)
+{
+ int ret;
+
+ ret = ioctl(fb_fd, FBIOBLANK, blank ? FB_BLANK_POWERDOWN : FB_BLANK_UNBLANK);
+ if (ret < 0)
+ perror("ioctl(): blank");
+}
+
+static void set_displayed_framebuffer(unsigned n)
+{
+ if (n > 1 || !double_buffered) return;
+
+ vi.yres_virtual = gr_framebuffer[0].height * 2;
+ vi.yoffset = n * gr_framebuffer[0].height;
+ vi.bits_per_pixel = gr_framebuffer[0].pixel_bytes * 8;
+ if (ioctl(fb_fd, FBIOPUT_VSCREENINFO, &vi) < 0) {
+ perror("active fb swap failed");
+ }
+ displayed_buffer = n;
+}
+
+static gr_surface fbdev_init(minui_backend* backend) {
+ int fd = open("/dev/graphics/fb0", O_RDWR);
+ if (fd == -1) {
+ perror("cannot open fb0");
+ return NULL;
+ }
+
+ fb_fix_screeninfo fi;
+ if (ioctl(fd, FBIOGET_FSCREENINFO, &fi) < 0) {
+ perror("failed to get fb0 info");
+ close(fd);
+ return NULL;
+ }
+
+ if (ioctl(fd, FBIOGET_VSCREENINFO, &vi) < 0) {
+ perror("failed to get fb0 info");
+ close(fd);
+ return NULL;
+ }
+
+ // We print this out for informational purposes only, but
+ // throughout we assume that the framebuffer device uses an RGBX
+ // pixel format. This is the case for every development device I
+ // have access to. For some of those devices (eg, hammerhead aka
+ // Nexus 5), FBIOGET_VSCREENINFO *reports* that it wants a
+ // different format (XBGR) but actually produces the correct
+ // results on the display when you write RGBX.
+ //
+ // If you have a device that actually *needs* another pixel format
+ // (ie, BGRX, or 565), patches welcome...
+
+ printf("fb0 reports (possibly inaccurate):\n"
+ " vi.bits_per_pixel = %d\n"
+ " vi.red.offset = %3d .length = %3d\n"
+ " vi.green.offset = %3d .length = %3d\n"
+ " vi.blue.offset = %3d .length = %3d\n",
+ vi.bits_per_pixel,
+ vi.red.offset, vi.red.length,
+ vi.green.offset, vi.green.length,
+ vi.blue.offset, vi.blue.length);
+
+ void* bits = mmap(0, fi.smem_len, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+ if (bits == MAP_FAILED) {
+ perror("failed to mmap framebuffer");
+ close(fd);
+ return NULL;
+ }
+
+ memset(bits, 0, fi.smem_len);
+
+ gr_framebuffer[0].width = vi.xres;
+ gr_framebuffer[0].height = vi.yres;
+ gr_framebuffer[0].row_bytes = fi.line_length;
+ gr_framebuffer[0].pixel_bytes = vi.bits_per_pixel / 8;
+ gr_framebuffer[0].data = reinterpret_cast<uint8_t*>(bits);
+ memset(gr_framebuffer[0].data, 0, gr_framebuffer[0].height * gr_framebuffer[0].row_bytes);
+
+ /* check if we can use double buffering */
+ if (vi.yres * fi.line_length * 2 <= fi.smem_len) {
+ double_buffered = true;
+
+ memcpy(gr_framebuffer+1, gr_framebuffer, sizeof(GRSurface));
+ gr_framebuffer[1].data = gr_framebuffer[0].data +
+ gr_framebuffer[0].height * gr_framebuffer[0].row_bytes;
+
+ gr_draw = gr_framebuffer+1;
+
+ } else {
+ double_buffered = false;
+
+ // Without double-buffering, we allocate RAM for a buffer to
+ // draw in, and then "flipping" the buffer consists of a
+ // memcpy from the buffer we allocated to the framebuffer.
+
+ gr_draw = (GRSurface*) malloc(sizeof(GRSurface));
+ memcpy(gr_draw, gr_framebuffer, sizeof(GRSurface));
+ gr_draw->data = (unsigned char*) malloc(gr_draw->height * gr_draw->row_bytes);
+ if (!gr_draw->data) {
+ perror("failed to allocate in-memory surface");
+ return NULL;
+ }
+ }
+
+ memset(gr_draw->data, 0, gr_draw->height * gr_draw->row_bytes);
+ fb_fd = fd;
+ set_displayed_framebuffer(0);
+
+ printf("framebuffer: %d (%d x %d)\n", fb_fd, gr_draw->width, gr_draw->height);
+
+ fbdev_blank(backend, true);
+ fbdev_blank(backend, false);
+
+ return gr_draw;
+}
+
+static gr_surface fbdev_flip(minui_backend* backend __unused) {
+ if (double_buffered) {
+#if defined(RECOVERY_BGRA)
+ // In case of BGRA, do some byte swapping
+ unsigned int idx;
+ unsigned char tmp;
+ unsigned char* ucfb_vaddr = (unsigned char*)gr_draw->data;
+ for (idx = 0 ; idx < (gr_draw->height * gr_draw->row_bytes);
+ idx += 4) {
+ tmp = ucfb_vaddr[idx];
+ ucfb_vaddr[idx ] = ucfb_vaddr[idx + 2];
+ ucfb_vaddr[idx + 2] = tmp;
+ }
+#endif
+ // Change gr_draw to point to the buffer currently displayed,
+ // then flip the driver so we're displaying the other buffer
+ // instead.
+ gr_draw = gr_framebuffer + displayed_buffer;
+ set_displayed_framebuffer(1-displayed_buffer);
+ } else {
+ // Copy from the in-memory surface to the framebuffer.
+ memcpy(gr_framebuffer[0].data, gr_draw->data,
+ gr_draw->height * gr_draw->row_bytes);
+ }
+ return gr_draw;
+}
+
+static void fbdev_exit(minui_backend* backend __unused) {
+ close(fb_fd);
+ fb_fd = -1;
+
+ if (!double_buffered && gr_draw) {
+ free(gr_draw->data);
+ free(gr_draw);
+ }
+ gr_draw = NULL;
+}