--- /dev/null
+
+#define _GNU_SOURCE
+
+#include <stdlib.h>
+#include <err.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <sys/ioctl.h>
+#include <string.h>
+#include <stdbool.h>
+#include <inttypes.h>
+
+#include <linux/fb.h>
+
+#include <libfdt.h>
+
+#include <file/file.h>
+#include <talloc/talloc.h>
+
+static const char *fbdev_name = "fb0";
+
+#define MAX_N_CELLS 4
+#define ADDRESS_PROP_SIZE 4096
+
+struct offb_ctx {
+ const char *dtb_name;
+ void *dtb;
+ int dtb_node;
+ const char *path;
+ struct fb_fix_screeninfo fscreeninfo;
+ struct fb_var_screeninfo vscreeninfo;
+};
+
+static int load_dtb(struct offb_ctx *ctx)
+{
+ char *buf;
+ int len;
+ int rc;
+
+ rc = read_file(ctx, ctx->dtb_name, &buf, &len);
+ if (rc) {
+ warn("error reading %s", ctx->dtb_name);
+ return rc;
+ }
+
+ rc = fdt_check_header(buf);
+ if (rc || (int)fdt_totalsize(buf) > len) {
+ warnx("invalid dtb: %s (rc %d)", ctx->dtb_name, rc);
+ return -1;
+ }
+
+ len = fdt_totalsize(buf) + ADDRESS_PROP_SIZE;
+
+ ctx->dtb = talloc_array(ctx, char, len);
+ if (!ctx->dtb) {
+ warn("Failed to allocate space for dtb\n");
+ return -1;
+ }
+ fdt_open_into(buf, ctx->dtb, len);
+
+ return 0;
+}
+
+static int fbdev_sysfs_lookup(struct offb_ctx *ctx)
+{
+ char *path, *linkpath, *nodepath;
+ int fd, node;
+ ssize_t rc __attribute__((unused));
+
+ path = talloc_asprintf(ctx, "/sys/class/graphics/%s", fbdev_name);
+ if (!path) {
+ warn("Failed to allocate space for sysfs path\n");
+ return -1;
+ }
+
+ fd = open(path, O_RDONLY | O_DIRECTORY);
+ if (fd < 0) {
+ warn("Can't open device %s in sysfs", fbdev_name);
+ return -1;
+ }
+
+ linkpath = talloc_zero_array(ctx, char, PATH_MAX + 1);
+ if (!linkpath) {
+ warn("Failed to allocate space for link path\n");
+ return -1;
+ }
+
+ rc = readlinkat(fd, "device/of_node", linkpath, PATH_MAX);
+ if (rc < 0) {
+ warn("Can't read of_node link for device %s", fbdev_name);
+ return -1;
+ }
+
+ /* readlinkat() returns a relative path such as:
+ *
+ * ../../../../../../../firmware/devicetree/base/pciex@n/…/vga@0
+ *
+ * We only need the path component from the device tree itself; so
+ * strip everything before /firmware/devicetree/base
+ */
+ nodepath = strstr(linkpath, "/firmware/devicetree/base/");
+ if (!nodepath) {
+ warnx("Can't resolve device tree link for device %s",
+ fbdev_name);
+ return -1;
+ }
+
+ nodepath += strlen("/firmware/devicetree/base");
+
+ node = fdt_path_offset(ctx->dtb, nodepath);
+ if (node < 0) {
+ warnx("Can't find node %s in device tree: %s",
+ nodepath, fdt_strerror(node));
+ return -1;
+ }
+
+ ctx->path = nodepath;
+ ctx->dtb_node = node;
+
+ return 0;
+}
+
+static int fbdev_device_query(struct offb_ctx *ctx)
+{
+ int fd, rc = -1;
+ char *path;
+
+ path = talloc_asprintf(ctx, "/dev/%s", fbdev_name);
+ if (!path) {
+ warn("Failed to allocate space for device path\n");
+ return -1;
+ }
+
+ fd = open(path, O_RDWR);
+ if (fd < 0) {
+ warn("Can't open fb device %s", path);
+ return -1;
+ }
+
+ rc = ioctl(fd, FBIOGET_VSCREENINFO, &ctx->vscreeninfo);
+ if (rc) {
+ warn("ioctl(FBIOGET_VSCREENINFO) failed");
+ goto out;
+ }
+
+ rc = ioctl(fd, FBIOGET_FSCREENINFO, &ctx->fscreeninfo);
+ if (rc) {
+ warn("ioctl(FBIOGET_FSCREENINFO) failed");
+ goto out;
+ }
+
+ fprintf(stderr, "Retrieved framebuffer details:\n");
+ fprintf(stderr, "device %s:\n", fbdev_name);
+ fprintf(stderr, " addr: %lx\n", ctx->fscreeninfo.smem_start);
+ fprintf(stderr, " len: %" PRIu32 "\n", ctx->fscreeninfo.smem_len);
+ fprintf(stderr, " line: %d\n", ctx->fscreeninfo.line_length);
+ fprintf(stderr, " res: %dx%d@%d\n", ctx->vscreeninfo.xres,
+ ctx->vscreeninfo.yres,
+ ctx->vscreeninfo.bits_per_pixel);
+
+ rc = 0;
+
+out:
+ close(fd);
+ return rc;
+}
+
+static char *next_dt_name(struct offb_ctx *ctx, const char **path)
+{
+ const char *c, *p;
+ char *name;
+
+ p = *path;
+
+ if (p[0] == '/')
+ p++;
+
+ if (p[0] == '\0')
+ return NULL;
+
+ c = strchrnul(p, '/');
+
+ name = talloc_strndup(ctx, p, c - p);
+
+ *path = c;
+
+ return name;
+}
+
+static uint64_t of_read_number(const fdt32_t *data, int n)
+{
+ uint64_t x;
+
+ x = fdt32_to_cpu(data[0]);
+ if (n > 1) {
+ x <<= 32;
+ x |= fdt32_to_cpu(data[1]);
+ }
+ return x;
+}
+
+/* Do a single translation across a PCI bridge. This results in either;
+ * - Translating a 2-cell CPU address into a 3-cell PCI address, or
+ * - Translating a 3-cell PCI address into a 3-cell PCI address with a
+ * different offset.
+ *
+ * To simplify translation we make some assumptions about addresses:
+ * Addresses are either 3 or 2 cells wide
+ * Size is always 2 cells wide
+ * The first cell of a 3 cell address is the PCI memory type
+ */
+static int do_translate(void *fdt, int node,
+ const fdt32_t *ranges, int range_size,
+ uint32_t *addr, uint32_t *size,
+ int *addr_cells, int *size_cells)
+{
+ uint64_t addr_current_base, addr_child_base, addr_size;
+ uint64_t addr_current, offset, new_addr;
+ uint64_t current_pci_flags, child_pci_flags;
+ int i, na, ns, cna, cns, prop_len;
+ const fdt32_t *prop;
+ const char *type;
+ bool pci = false;
+
+ type = fdt_getprop(fdt, node, "device_type", NULL);
+ pci = type && (!strcmp(type, "pci") || !strcmp(type, "pciex"));
+
+ /* We don't translate at vga@0, so we should always see a pci or
+ * pciex device_type */
+ if (!pci)
+ return -1;
+
+ if (range_size == 0) {
+ fprintf(stderr, "Empty ranges property, 1:1 translation\n");
+ return 0;
+ }
+
+ /* Number of cells for address and size at current level */
+ na = *addr_cells;
+ ns = *size_cells;
+
+ /* Number of cells for address and size at child level */
+ prop = fdt_getprop(fdt, node, "#address-cells", &prop_len);
+ cna = prop ? fdt32_to_cpu(*prop) : 2;
+ prop = fdt_getprop(fdt, node, "#size-cells", &prop_len);
+ cns = prop ? fdt32_to_cpu(*prop) : 2;
+
+ /* We're translating back to a PCI address, so the size should grow */
+ if (na > cna) {
+ fprintf(stderr, "na > cna, unexpected\n");
+ return -1;
+ }
+
+ /* If the current address is a PCI address, its type should match the
+ * type of every subsequent child address */
+ current_pci_flags = na > 2 ? of_read_number(addr, 1) : 0;
+ child_pci_flags = cna > 2 ? of_read_number(ranges, 1) : 0;
+ if (current_pci_flags != 0 && current_pci_flags != child_pci_flags) {
+ fprintf(stderr, "Unexpected change in flags: %lx, %lx\n",
+ current_pci_flags, child_pci_flags);
+ return -1;
+ }
+
+ if (ns != cns) {
+ fprintf(stderr, "Unexpected change in #size-cells: %d vs %d\n",
+ ns, cns);
+ return -1;
+ }
+
+ /*
+ * The ranges property is of the form
+ * < upstream addr base > < downstream addr base > < size >
+ * The current address stored in addr is similarly of the form
+ * < current address > < size >
+ * Where either address base and the current address can be a 2-cell
+ * CPU address or a 3-cell PCI address.
+ *
+ * For PCI addresses ignore the type flag in the first cell and use the
+ * 64-bit address in the remaining 2 cells.
+ */
+ if (na > 2) {
+ addr_current_base = of_read_number(ranges + cna + 1, na - 1);
+ addr_current = of_read_number(addr + 1, na - 1);
+ } else {
+ addr_current_base = of_read_number(ranges + cna, na);
+ addr_current = of_read_number(addr, na);
+ }
+ if (cna > 2)
+ addr_child_base = of_read_number(ranges + 1, cna - 1);
+ else
+ addr_child_base = of_read_number(ranges, cna);
+
+ /*
+ * Perform the actual translation. Find the offset of the current
+ * address from the upstream base, and add the offset to the
+ * downstream base to find the new address.
+ * The new address will be cna-cells wide, inheriting child_pci_flags
+ * as the memory type.
+ */
+ addr_size = of_read_number(size, ns);
+ offset = addr_current - addr_current_base;
+ new_addr = addr_child_base + offset;
+
+ memset(addr, 0, *addr_cells);
+ memset(size, 0, *size_cells);
+ *addr_cells = cna;
+ *size_cells = cns;
+
+ /* Update the current address in addr.
+ * It's highly unlikely any translation will leave us with a 2-cell
+ * CPU address, but for completeness only include PCI flags if the
+ * child offset was definitely a PCI address */
+ if (*addr_cells > 2)
+ addr[0] = cpu_to_fdt32(child_pci_flags);
+ for (i = *addr_cells - 1; i >= *addr_cells - 2; i--) {
+ addr[i] = cpu_to_fdt32(new_addr & 0xffffffff);
+ new_addr >>= 32;
+ }
+ for (i = *size_cells - 1; i >= 0; i--) {
+ size[i] = cpu_to_fdt32(addr_size & 0xffffffff);
+ addr_size >>= 32;
+ }
+
+ fprintf(stderr, "New address:\n\t");
+ for (i = 0; i < *addr_cells; i++)
+ fprintf(stderr, " %lx ", of_read_number(&addr[i], 1));
+ fprintf(stderr, "\n");
+
+ return 0;
+}
+
+static int create_translated_addresses(struct offb_ctx *ctx,
+ int dev_node, const char *path,
+ uint64_t in_addr, uint64_t in_size,
+ fdt32_t *reg, int reg_cells)
+{
+ uint32_t addr[MAX_N_CELLS], size[MAX_N_CELLS];
+ int addr_cells, size_cells, node, prop_len, ranges_len, rc, i;
+ const fdt32_t *ranges, *prop;
+ char *name;
+
+ prop = fdt_getprop(ctx->dtb, 0, "#address-cells", &prop_len);
+ addr_cells = prop ? fdt32_to_cpu(*prop) : 2;
+
+ prop = fdt_getprop(ctx->dtb, 0, "#size-cells", &prop_len);
+ size_cells = prop ? fdt32_to_cpu(*prop) : 2;
+
+ memset(addr, 0, sizeof(uint32_t) * MAX_N_CELLS);
+ for (i = addr_cells - 1; i >= 0; i--) {
+ addr[i] = cpu_to_fdt32(in_addr & 0xffffffff);
+ in_addr >>= 32;
+ }
+ memset(size, 0, sizeof(uint32_t) * MAX_N_CELLS);
+ for (i = size_cells - 1; i >= 0; i--) {
+ size[i] = cpu_to_fdt32(in_size & 0xffffffff);
+ in_size >>= 32;
+ }
+
+ node = 0;
+ for (;;) {
+ /* get the name of the next child node to 'node' */
+ name = next_dt_name(ctx, &path);
+ if (!name)
+ return -1;
+
+ node = fdt_subnode_offset(ctx->dtb, node, name);
+ if (node < 0)
+ return -1;
+ if (node == dev_node)
+ break;
+
+ ranges = fdt_getprop(ctx->dtb, node, "ranges", &ranges_len);
+ if (!ranges)
+ return -1;
+
+ rc = do_translate(ctx->dtb, node, ranges, ranges_len,
+ addr, size, &addr_cells, &size_cells);
+ if (rc)
+ return -1;
+ }
+
+ fprintf(stderr, "Final address:\n\t");
+ for (i = 0; i < addr_cells; i++)
+ fprintf(stderr, " %lx ", of_read_number(&addr[i], 1));
+ fprintf(stderr, "\n");
+
+ if (addr_cells + size_cells > reg_cells) {
+ fprintf(stderr, "Error: na + ns larger than reg\n");
+ return -1;
+ }
+
+ memcpy(reg, addr, sizeof(fdt32_t) * addr_cells);
+ memcpy(reg + addr_cells, size, sizeof(fdt32_t) * size_cells);
+
+ return 0;
+}
+
+#define fdt_set_check(dtb, node, fn, prop, ...) \
+ do { \
+ int __x = fn(dtb, node, prop, __VA_ARGS__); \
+ if (__x) { \
+ warnx("failed to update device tree (%s): %s", \
+ prop, fdt_strerror(__x)); \
+ return -1; \
+ } \
+ } while (0);
+
+static int populate_devicetree(struct offb_ctx *ctx)
+{
+ fdt32_t reg[5];
+ void *dtb = ctx->dtb;
+ int rc, node = ctx->dtb_node;
+
+ memset(reg, 0, sizeof(reg));
+ rc = create_translated_addresses(ctx, node, ctx->path,
+ ctx->fscreeninfo.smem_start,
+ ctx->fscreeninfo.smem_len,
+ reg, 5);
+
+ if (rc) {
+ fprintf(stderr, "Failed to translate address\n");
+ return rc;
+ }
+
+ fdt_set_check(dtb, node, fdt_setprop_string, "device_type", "display");
+
+ fdt_set_check(dtb, node, fdt_setprop, "assigned-addresses",
+ reg, sizeof(reg));
+
+ fdt_set_check(dtb, node, fdt_setprop_cell,
+ "width", ctx->vscreeninfo.xres);
+ fdt_set_check(dtb, node, fdt_setprop_cell,
+ "height", ctx->vscreeninfo.yres);
+ fdt_set_check(dtb, node, fdt_setprop_cell,
+ "depth", ctx->vscreeninfo.bits_per_pixel);
+
+ fdt_set_check(dtb, node, fdt_setprop, "little-endian", NULL, 0);
+ fdt_set_check(dtb, node, fdt_setprop, "linux,opened", NULL, 0);
+ fdt_set_check(dtb, node, fdt_setprop, "linux,boot-display", NULL, 0);
+
+ return 0;
+}
+
+static int write_devicetree(struct offb_ctx *ctx)
+{
+ int rc;
+
+ fdt_pack(ctx->dtb);
+
+ rc = replace_file(ctx->dtb_name, ctx->dtb, fdt_totalsize(ctx->dtb));
+ if (rc)
+ warn("failed to write file %s", ctx->dtb_name);
+
+ return rc;
+}
+
+
+int main(void)
+{
+ struct offb_ctx *ctx;
+ int rc;
+
+ ctx = talloc_zero(NULL, struct offb_ctx);
+
+ ctx->dtb_name = getenv("boot_dtb");
+ if (!ctx->dtb_name) {
+ talloc_free(ctx);
+ return EXIT_SUCCESS;
+ }
+
+ rc = load_dtb(ctx);
+ if (rc)
+ goto out;
+
+ rc = fbdev_sysfs_lookup(ctx);
+ if (rc)
+ goto out;
+
+ rc = fbdev_device_query(ctx);
+ if (rc)
+ goto out;
+
+ rc = populate_devicetree(ctx);
+ if (rc)
+ goto out;
+
+ rc = write_devicetree(ctx);
+
+out:
+ talloc_free(ctx);
+ return rc ? EXIT_FAILURE : EXIT_SUCCESS;
+}
projects / petitboot / commitdiff