diff --git a/hexagonrpcd/apps_std.c b/hexagonrpcd/apps_std.c
index ff4d5a7..12991f2 100644
--- a/hexagonrpcd/apps_std.c
+++ b/hexagonrpcd/apps_std.c
@@ -120,6 +120,40 @@ static uint32_t apps_std_fread(void *data,
 	return 0;
 }
 
+static uint32_t apps_std_fwrite(void *data,
+				const struct fastrpc_io_buffer *inbufs,
+				struct fastrpc_io_buffer *outbufs)
+{
+	struct apps_std_ctx *ctx = data;
+	const struct {
+		uint32_t fd;
+		uint32_t buf_size;
+	} *first_in = inbufs[0].p;
+	struct {
+		uint32_t written;
+		uint32_t is_eof;
+	} *first_out = outbufs[0].p;
+	ssize_t ret;
+
+	ret = hexagonfs_write(ctx->fds, first_in->fd,
+			      first_in->buf_size, inbufs[1].p);
+	if (ret < 0) {
+		fprintf(stderr, "Could not write file: %s\n", strerror(-ret));
+		return AEE_EFAILED;
+	}
+
+#ifdef HEXAGONRPC_VERBOSE
+	printf("write(%u, %u) -> %ld\n", first_in->fd,
+					  first_in->buf_size,
+					  ret);
+#endif
+
+	first_out->written = ret;
+	first_out->is_eof = 0;
+
+	return 0;
+}
+
 static uint32_t apps_std_fseek(void *data,
 			       const struct fastrpc_io_buffer *inbufs,
 			       struct fastrpc_io_buffer *outbufs)
@@ -166,11 +200,6 @@ static uint32_t apps_std_fopen_with_env(void *data,
 		return AEE_EBADPARM;
 
 	rw_mode = ((const char *) inbufs[4].p)[0];
-	if (rw_mode == 'w' || rw_mode == 'a') {
-		fprintf(stderr, "Tried to open %s for writing\n",
-				(const char *) inbufs[3].p);
-		return AEE_EUNSUPPORTED;
-	}
 
 	if (!strcmp(inbufs[1].p, "ADSP_LIBRARY_PATH")) {
 		dirfd = ctx->adsp_library_dirfd;
@@ -188,7 +217,8 @@ static uint32_t apps_std_fopen_with_env(void *data,
 		return AEE_EFAILED;
 	}
 
-	fd = hexagonfs_openat(ctx->fds, ctx->rootfd, dirfd, inbufs[3].p);
+	fd = hexagonfs_openat(ctx->fds, ctx->rootfd, dirfd, inbufs[3].p,
+			      rw_mode == 'w' || rw_mode == 'a');
 	if (fd < 0) {
 		fprintf(stderr, "Could not open %s: %s\n",
 				(const char *) inbufs[3].p,
@@ -220,7 +250,8 @@ static uint32_t apps_std_opendir(void *data,
 	if (((const char *) inbufs[1].p)[inbufs[1].s - 1] != 0)
 		return AEE_EBADPARM;
 
-	ret = hexagonfs_openat(ctx->fds, ctx->rootfd, ctx->rootfd, inbufs[1].p);
+	ret = hexagonfs_openat(ctx->fds, ctx->rootfd, ctx->rootfd, inbufs[1].p,
+			       false);
 	if (ret < 0) {
 		fprintf(stderr, "Could not open %s: %s\n",
 				(const char *) inbufs[1].p,
@@ -313,7 +344,8 @@ static uint32_t apps_std_stat(void *data,
 	if (((const char *) inbufs[1].p)[inbufs[1].s - 1] != 0)
 		return AEE_EBADPARM;
 
-	fd = hexagonfs_openat(ctx->fds, ctx->rootfd, ctx->adsp_library_dirfd, pathname);
+	fd = hexagonfs_openat(ctx->fds, ctx->rootfd, ctx->adsp_library_dirfd,
+			      pathname, false);
 	if (fd < 0) {
 		fprintf(stderr, "Could not open %s: %s\n",
 				pathname, strerror(-fd));
@@ -373,11 +405,13 @@ struct fastrpc_interface *fastrpc_apps_std_init(struct hexagonfs_dirent *root)
 	ctx->adsp_avs_cfg_dirfd = hexagonfs_openat(ctx->fds,
 						   ctx->rootfd,
 						   ctx->rootfd,
-						   "/vendor/etc/acdbdata/");
+						   "/vendor/etc/acdbdata/",
+						   false);
 	ctx->adsp_library_dirfd = hexagonfs_openat(ctx->fds,
 						   ctx->rootfd,
 						   ctx->rootfd,
-						   "/usr/lib/qcom/adsp/");
+						   "/usr/lib/qcom/adsp/",
+						   false);
 
 	iface->data = ctx;
 
@@ -420,7 +454,10 @@ static const struct fastrpc_function_impl apps_std_procs[] = {
 		.def = &apps_std_fread_def,
 		.impl = apps_std_fread,
 	},
-	{ .def = NULL, .impl = NULL, },
+	{
+		.def = &apps_std_fwrite_def,
+		.impl = apps_std_fwrite,
+	},
 	{ .def = NULL, .impl = NULL, },
 	{ .def = NULL, .impl = NULL, },
 	{ .def = NULL, .impl = NULL, },
diff --git a/hexagonrpcd/hexagonfs.c b/hexagonrpcd/hexagonfs.c
index bd9f353..91d4659 100644
--- a/hexagonrpcd/hexagonfs.c
+++ b/hexagonrpcd/hexagonfs.c
@@ -139,7 +139,8 @@ err:
 	return ret;
 }
 
-int hexagonfs_openat(struct hexagonfs_fd **fds, int rootfd, int dirfd, const char *name)
+int hexagonfs_openat(struct hexagonfs_fd **fds, int rootfd, int dirfd,
+		     const char *name, bool create)
 {
 	struct hexagonfs_fd *fd;
 	const char *curr = name;
@@ -169,7 +170,7 @@ int hexagonfs_openat(struct hexagonfs_fd **fds, int rootfd, int dirfd, const cha
 		} else if (!strcmp(segment, "..")) {
 			fd = pop_dir(fd, fds[rootfd]);
 		} else {
-			ret = fd->ops->openat(fd, segment, expect_dir, &fd);
+			ret = fd->ops->openat(fd, segment, expect_dir, create, &fd);
 		}
 
 	next:
@@ -244,6 +245,24 @@ ssize_t hexagonfs_read(struct hexagonfs_fd **fds, int fileno, size_t size, void
 	return fd->ops->read(fd, size, ptr);
 }
 
+ssize_t hexagonfs_write(struct hexagonfs_fd **fds, int fileno,
+			size_t size, const void *ptr)
+{
+	struct hexagonfs_fd *fd;
+
+	if (fileno < 0 || fileno >= HEXAGONFS_MAX_FD)
+		return -EBADF;
+
+	fd = fds[fileno];
+	if (fd == NULL)
+		return -EBADF;
+
+	if (fd->ops->write == NULL)
+		return -EROFS;
+
+	return fd->ops->write(fd, size, ptr);
+}
+
 int hexagonfs_readdir(struct hexagonfs_fd **fds, int fileno, size_t ent_size, char *ent)
 {
 	struct hexagonfs_fd *fd;
diff --git a/hexagonrpcd/hexagonfs.h b/hexagonrpcd/hexagonfs.h
index 7682604..2539afe 100644
--- a/hexagonrpcd/hexagonfs.h
+++ b/hexagonrpcd/hexagonfs.h
@@ -37,9 +37,11 @@ struct hexagonfs_file_ops {
 	int (*openat)(struct hexagonfs_fd *dir,
 		      const char *segment,
 		      bool expect_dir,
+		      bool create,
 		      struct hexagonfs_fd **out);
 	int (*readdir)(struct hexagonfs_fd *fd, size_t size, char *out);
 	ssize_t (*read)(struct hexagonfs_fd *fd, size_t size, void *ptr);
+	ssize_t (*write)(struct hexagonfs_fd *fd, size_t size, const void *ptr);
 	int (*stat)(struct hexagonfs_fd *fd, struct stat *stats);
 	int (*seek)(struct hexagonfs_fd *fd, off_t off, int whence);
 };
@@ -70,8 +72,11 @@ extern struct hexagonfs_file_ops hexagonfs_plat_subtype_name_ops;
 extern struct hexagonfs_file_ops hexagonfs_virt_dir_ops;
 
 int hexagonfs_open_root(struct hexagonfs_fd **fds, struct hexagonfs_dirent *root);
-int hexagonfs_openat(struct hexagonfs_fd **fds, int rootfd, int dirfd, const char *name);
+int hexagonfs_openat(struct hexagonfs_fd **fds, int rootfd, int dirfd,
+		     const char *name, bool create);
 int hexagonfs_close(struct hexagonfs_fd **fds, int fileno);
+ssize_t hexagonfs_write(struct hexagonfs_fd **fds, int fileno,
+			size_t size, const void *ptr);
 
 int hexagonfs_fstat(struct hexagonfs_fd **fds, int fileno, struct stat *stats);
 int hexagonfs_lseek(struct hexagonfs_fd **fds, int fileno, off_t pos, int whence);
diff --git a/hexagonrpcd/hexagonfs_mapped.c b/hexagonrpcd/hexagonfs_mapped.c
index fd28c8c..83af835 100644
--- a/hexagonrpcd/hexagonfs_mapped.c
+++ b/hexagonrpcd/hexagonfs_mapped.c
@@ -61,7 +61,14 @@ static int mapped_from_dirent(const void *dirent_data, bool dir, void **fd_data)
 	if (dir)
 		flags |= O_DIRECTORY;
 
-	ctx->fd = open(name, flags);
+	/*
+	 * The DSP updates some of the files it is served, the sensor registry
+	 * version among them. Prefer read-write and fall back, so a read-only
+	 * mount or a file we may not write still opens.
+	 */
+	ctx->fd = dir ? -1 : open(name, (flags & ~O_ACCMODE) | O_RDWR);
+	if (ctx->fd == -1)
+		ctx->fd = open(name, flags);
 	if (ctx->fd == -1) {
 		ret = -errno;
 		goto err;
@@ -81,6 +88,7 @@ err:
 static int mapped_openat(struct hexagonfs_fd *dir,
 			 const char *segment,
 			 bool expect_dir,
+			 bool create,
 			 struct hexagonfs_fd **out)
 {
 	struct mapped_ctx *dir_ctx = dir->data;
@@ -102,7 +110,24 @@ static int mapped_openat(struct hexagonfs_fd *dir,
 	if (expect_dir)
 		flags |= O_DIRECTORY;
 
-	ctx->fd = openat(dir_ctx->fd, segment, flags);
+	if (expect_dir) {
+		ctx->fd = -1;
+	} else {
+		int rw = (flags & ~O_ACCMODE) | O_RDWR;
+
+		/*
+		 * The DSP creates files under the directories it is served,
+		 * numbered registry entries among them, so honour a create
+		 * request rather than failing the open.
+		 */
+		if (create)
+			ctx->fd = openat(dir_ctx->fd, segment,
+					 rw | O_CREAT, 0644);
+		else
+			ctx->fd = openat(dir_ctx->fd, segment, rw);
+	}
+	if (ctx->fd == -1)
+		ctx->fd = openat(dir_ctx->fd, segment, flags);
 	if (ctx->fd == -1) {
 		ret = -errno;
 		goto err_free_fd;
@@ -138,6 +163,19 @@ static ssize_t mapped_read(struct hexagonfs_fd *fd, size_t size, void *out)
 	return ret;
 }
 
+static ssize_t mapped_write(struct hexagonfs_fd *fd, size_t size,
+			    const void *in)
+{
+	struct mapped_ctx *ctx = fd->data;
+	ssize_t ret;
+
+	ret = write(ctx->fd, in, size);
+	if (ret < 0)
+		return -errno;
+
+	return ret;
+}
+
 static int mapped_readdir(struct hexagonfs_fd *fd, size_t size, char *out)
 {
 	struct mapped_ctx *ctx = fd->data;
@@ -236,10 +274,11 @@ static int mapped_or_empty_from_dirent(const void *dirent_data, bool dir, void *
 static int mapped_or_empty_openat(struct hexagonfs_fd *dir,
 				  const char *segment,
 				  bool expect_dir,
+				  bool create,
 				  struct hexagonfs_fd **out)
 {
 	if (dir->data)
-		return mapped_openat(dir, segment, expect_dir, out);
+		return mapped_openat(dir, segment, expect_dir, create, out);
 	else
 		return -ENOENT;
 }
@@ -327,6 +366,7 @@ struct hexagonfs_file_ops hexagonfs_mapped_ops = {
 	.from_dirent = mapped_from_dirent,
 	.openat = mapped_openat,
 	.read = mapped_read,
+	.write = mapped_write,
 	.readdir = mapped_readdir,
 	.seek = mapped_seek,
 	.stat = mapped_stat,
diff --git a/hexagonrpcd/hexagonfs_plat_subtype_name.c b/hexagonrpcd/hexagonfs_plat_subtype_name.c
index d20916f..9716dd4 100644
--- a/hexagonrpcd/hexagonfs_plat_subtype_name.c
+++ b/hexagonrpcd/hexagonfs_plat_subtype_name.c
@@ -68,6 +68,7 @@ static int plat_subtype_name_from_dirent(const void *dirent_data,
 static int plat_subtype_name_openat(struct hexagonfs_fd *dir,
 			const char *segment,
 			bool expect_dir,
+			bool create,
 			struct hexagonfs_fd **out)
 {
 	return -ENOTDIR;
diff --git a/hexagonrpcd/hexagonfs_virt_dir.c b/hexagonrpcd/hexagonfs_virt_dir.c
index eaba520..23fe016 100644
--- a/hexagonrpcd/hexagonfs_virt_dir.c
+++ b/hexagonrpcd/hexagonfs_virt_dir.c
@@ -63,6 +63,7 @@ static int virt_dir_from_dirent(const void *dirent_data, bool dir, void **fd_dat
 static int virt_dir_openat(struct hexagonfs_fd *dir,
 			   const char *segment,
 			   bool expect_dir,
+			   bool create,
 			   struct hexagonfs_fd **out)
 {
 	const struct hexagonfs_dirent *const **dirlist = dir->data;
diff --git a/hexagonrpcd/interfaces/apps_std.def b/hexagonrpcd/interfaces/apps_std.def
index 2fbbdb1..35441e1 100644
--- a/hexagonrpcd/interfaces/apps_std.def
+++ b/hexagonrpcd/interfaces/apps_std.def
@@ -28,6 +28,7 @@ HEXAGONRPC_DEFINE_REMOTE_METHOD(1, apps_std_freopen, 1, 0, 1, 1)
 HEXAGONRPC_DEFINE_REMOTE_METHOD(2, apps_std_fflush, 8, 0, 0, 0)
 HEXAGONRPC_DEFINE_REMOTE_METHOD(3, apps_std_fclose, 1, 0, 0, 0)
 HEXAGONRPC_DEFINE_REMOTE_METHOD(4, apps_std_fread, 1, 0, 2, 1)
+HEXAGONRPC_DEFINE_REMOTE_METHOD(5, apps_std_fwrite, 1, 1, 2, 0)
 HEXAGONRPC_DEFINE_REMOTE_METHOD(9, apps_std_fseek, 3, 0, 0, 0)
 HEXAGONRPC_DEFINE_REMOTE_METHOD(19, apps_std_fopen_with_env, 0, 4, 1, 0)
 HEXAGONRPC_DEFINE_REMOTE_METHOD(26, apps_std_opendir, 0, 1, 2, 0)
diff --git a/hexagonrpcd/listener.c b/hexagonrpcd/listener.c
index e298688..b78a522 100644
--- a/hexagonrpcd/listener.c
+++ b/hexagonrpcd/listener.c
@@ -312,8 +312,24 @@ int run_fastrpc_listener(int fd,
 		ret = invoke_requested_procedure(n_ifaces, ifaces,
 						 handle, sc, &result,
 						 decoded, &returned);
-		if (ret)
-			break;
+		/*
+		 * A method we do not implement is the DSP's problem, not ours.
+		 * The error is already in `result` and goes back on the next
+		 * pass, so keep serving instead of tearing down the whole file
+		 * service over one unknown call.
+		 */
+		if (ret) {
+			ret = 0;
+			returned = NULL;
+			n_outbufs = 0;
+
+			if (decoded != NULL) {
+				iobuf_free(REMOTE_SCALARS_INBUFS(sc), decoded);
+				decoded = NULL;
+			}
+
+			continue;
+		}
 
 		if (decoded != NULL)
 			iobuf_free(REMOTE_SCALARS_INBUFS(sc), decoded);
diff --git a/hexagonrpcd/rpcd_builder.c b/hexagonrpcd/rpcd_builder.c
index d374958..b0d25a3 100644
--- a/hexagonrpcd/rpcd_builder.c
+++ b/hexagonrpcd/rpcd_builder.c
@@ -31,6 +31,9 @@
 #define SENSORS_CONFIG		"/sensors/config/"
 #define SENSORS_REGISTRY	"/sensors/registry/"
 #define SNS_REG_CONFIG		"/sensors/sns_reg.conf"
+#define SENSORS_DIR		"/sensors/"
+#define PROJECT_INFO		"/project_info/"
+#define OPPO_VERSION		"/oppoVersion/"
 #define SYSFS_SOCINFO		"/socinfo/"
 
 static struct hexagonfs_dirent *hfs_mkdir(const char *name, size_t n_ents, ...)
@@ -120,7 +123,11 @@ struct hexagonfs_dirent *construct_root_dir(const char *prefix, const char *dsp)
 	acdbdata = malloc(n_prefix + strlen(ACDBDATA) + 1);
 	sns_cfg = malloc(n_prefix + strlen(SENSORS_CONFIG) + 1);
 	sns_reg = malloc(n_prefix + strlen(SENSORS_REGISTRY) + 1);
+	char *sensors_dir, *project_info, *oppo_version;
 	sns_reg_config = malloc(n_prefix + strlen(SNS_REG_CONFIG) + 1);
+	sensors_dir = malloc(n_prefix + strlen(SENSORS_DIR) + 1);
+	project_info = malloc(n_prefix + strlen(PROJECT_INFO) + 1);
+	oppo_version = malloc(n_prefix + strlen(OPPO_VERSION) + 1);
 	socinfo = malloc(n_prefix + strlen(SYSFS_SOCINFO) + 1);
 
 	dsp_libs = malloc(n_prefix + strlen(DSP_LIBS) + strlen(dsp) + 1);
@@ -145,6 +152,21 @@ struct hexagonfs_dirent *construct_root_dir(const char *prefix, const char *dsp)
 		strcat(sns_reg_config, SNS_REG_CONFIG);
 	}
 
+	if (sensors_dir != NULL) {
+		strcpy(sensors_dir, prefix);
+		strcat(sensors_dir, SENSORS_DIR);
+	}
+
+	if (project_info != NULL) {
+		strcpy(project_info, prefix);
+		strcat(project_info, PROJECT_INFO);
+	}
+
+	if (oppo_version != NULL) {
+		strcpy(oppo_version, prefix);
+		strcat(oppo_version, OPPO_VERSION);
+	}
+
 	if (socinfo != NULL) {
 		strcpy(socinfo, prefix);
 		strcat(socinfo, SYSFS_SOCINFO);
@@ -162,9 +184,7 @@ struct hexagonfs_dirent *construct_root_dir(const char *prefix, const char *dsp)
 	 */
 	persist_dir = hfs_mkdir("persist", 1,
 				hfs_mkdir("sensors", 1,
-					hfs_mkdir("registry", 1,
-						hfs_map("registry", sns_reg)
-					)
+					hfs_map("registry", sensors_dir)
 				)
 		      );
 
@@ -182,17 +202,21 @@ struct hexagonfs_dirent *construct_root_dir(const char *prefix, const char *dsp)
 				)
 			);
 
-	return hfs_mkdir("/", 6,
+	return hfs_mkdir("/", 7,
+			hfs_mkdir("proc", 1,
+				hfs_map_or_empty("oppoVersion", oppo_version)
+			),
 			hfs_mkdir("mnt", 1,
 				hfs_mkdir("vendor", 1,
 					persist_dir
 				)
 			),
 			persist_dir,
-			hfs_mkdir("sys", 1,
+			hfs_mkdir("sys", 2,
 				hfs_mkdir("devices", 1,
 					hfs_map_or_empty("soc0", socinfo)
-				)
+				),
+				hfs_map_or_empty("project_info", project_info)
 			),
 			hfs_mkdir("system", 1,
 				vendor_dir