virtio: Add support for files

Add an implementation of virtio-fs files, including looking them up and
reading them.

Signed-off-by: Simon Glass <sjg@chromium.org>

drivers/virtio/Makefile

@@ -12,4 +12,4 @@ obj-$(CONFIG_VIRTIO_SANDBOX_EMUL) += sandbox_emul.o emul_blk.o
 obj-$(CONFIG_VIRTIO_NET) += virtio_net.o
 obj-$(CONFIG_VIRTIO_BLK) += virtio_blk.o
 obj-$(CONFIG_VIRTIO_RNG) += virtio_rng.o
-obj-$(CONFIG_VIRTIO_FS) += fs.o fs_dir.o
+obj-$(CONFIG_VIRTIO_FS) += fs.o fs_dir.o fs_file.o

drivers/virtio/fs_dir.c

@@ -105,6 +105,22 @@ static int virtio_fs_dir_close(struct udevice *dev, struct fs_dir_stream *strm)
 	return 0;
 }
 
+static int open_file(struct udevice *dev, const char *leaf,
+		     enum dir_open_flags_t oflags, struct udevice **filp)
+{
+	struct udevice *fil;
+	int ret;
+
+	log_debug("start '%s'\n", leaf);
+	ret = virtio_fs_setup_file(dev, leaf, oflags, &fil);
+	log_debug("ret %d\n", ret);
+	if (ret)
+		return log_msg_ret("dof", ret);
+	*filp = fil;
+
+	return 0;
+}
+
 static int virtio_fs_dir_remove(struct udevice *dev)
 {
 	struct virtio_fs_dir_priv *dir_priv = dev_get_priv(dev);
@@ -124,6 +140,7 @@ static struct dir_ops virtio_fs_dir_ops = {
 	.open	= virtio_fs_dir_open,
 	.read	= virtio_fs_dir_read,
 	.close	= virtio_fs_dir_close,
+	.open_file	= open_file,
 };
 
 static const struct udevice_id dir_ids[] = {

drivers/virtio/fs_file.c

@@ -0,0 +1,136 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * U-Boot Virtio-FS files
+ *
+ * Copyright 2025 Simon Glass <sjg@chromium.org>
+ *
+ * Supports access to files in virtio-fs
+ */
+
+#define LOG_CATEGORY	UCLASS_VIRTIO
+
+#include <dm.h>
+#include <file.h>
+#include <fs.h>
+#include <malloc.h>
+#include <virtio_fs.h>
+#include <dm/device-internal.h>
+#include <dm/lists.h>
+#include <linux/fuse.h>
+#include "fs_internal.h"
+
+/**
+ * struct file_priv - Information about a virtio file
+ *
+ * @flags: Open-mode flags
+ * @backing_id: Backing ID for the file
+ * @fh: Unique filehandle for the file
+ * @size: Size of the file
+ */
+struct file_priv {
+	u64 nodeid;
+	enum dir_open_flags_t flags;
+	u64 fh;
+};
+
+static ssize_t virtio_fs_read_iter(struct udevice *dev, struct iov_iter *iter,
+				   loff_t pos)
+{
+	struct file_priv *priv = dev_get_priv(dev);
+	struct udevice *dir = dev_get_parent(dev);
+	struct udevice *fsdev = dev_get_parent(dir);
+	ssize_t ret;
+
+	log_debug("start dev '%s' len %zx\n", dev->name, iter->count);
+	ret = virtio_fs_read(fsdev, priv->nodeid, priv->fh, pos,
+			     iter_iov_ptr(iter), iter_iov_avail(iter));
+	if (ret < 0)
+		return log_msg_ret("vfr", ret);
+	iter_advance(iter, ret);
+	log_debug("read %zx bytes\n", ret);
+
+	return ret;
+}
+
+static int virtio_fs_file_remove(struct udevice *dev)
+{
+	struct virtio_fs_dir_priv *dir_priv = dev_get_priv(dev);
+
+	if (*dir_priv->path) {
+		int ret;
+
+		ret = virtio_fs_forget(dev, dir_priv->inode);
+		if (ret)
+			return log_msg_ret("vfr", ret);
+	}
+
+	return 0;
+}
+
+static struct file_ops virtio_fs_file_ops = {
+	.read_iter	= virtio_fs_read_iter,
+};
+
+static const struct udevice_id file_ids[] = {
+	{ .compatible = "virtio-fs,file" },
+	{ }
+};
+
+U_BOOT_DRIVER(virtio_fs_file) = {
+	.name	= "virtio_fs_file",
+	.id	= UCLASS_FILE,
+	.of_match = file_ids,
+	.remove	= virtio_fs_file_remove,
+	.ops	= &virtio_fs_file_ops,
+	.priv_auto	= sizeof(struct file_priv),
+	.flags	= DM_FLAG_ACTIVE_DMA,
+};
+
+int virtio_fs_setup_file(struct udevice *dir, const char *leaf,
+			 enum dir_open_flags_t oflags, struct udevice **devp)
+{
+	struct udevice *fil, *fsdev = dev_get_parent(dir);
+	struct virtio_fs_dir_priv *dir_priv = dev_get_priv(dir);
+	struct file_uc_priv *file_uc_priv;
+	struct file_priv *file_priv;
+	struct fuse_entry_out out;
+	uint flags;
+	u64 fh;
+	int ret;
+
+	log_debug("dir '%s' inode %llx leaf '%s' oflags %d\n", dir->name,
+		  dir_priv->inode, leaf, oflags);
+
+	ret = virtio_fs_lookup_(fsdev, dir_priv->inode, leaf, &out);
+	if (ret) {
+		log_debug("lookup fail ret=%d\n", ret);
+		return log_msg_ret("vfl", ret);
+	}
+
+	log_debug("open nodeid %lld\n", out.nodeid);
+	ret = virtio_fs_open_file(fsdev, out.nodeid, oflags, &fh, &flags);
+	if (ret) {
+		log_debug("fail ret=%d\n", ret);
+		return log_msg_ret("vfo", ret);
+	}
+	log_debug("result fh %llx flags %x\n", fh, flags);
+
+	ret = file_add_probe(dir, DM_DRIVER_REF(virtio_fs_file), leaf,
+			     out.attr.size, flags, &fil);
+	if (ret) {
+		/* TODO: close file? */
+		return log_msg_ret("vfp", ret);
+	}
+
+	file_priv = dev_get_priv(fil);
+	file_priv->nodeid = out.nodeid;
+	file_priv->fh = fh;
+	file_priv->flags = flags;
+	file_uc_priv = dev_get_uclass_priv(fil);
+
+	log_debug("opened file dev '%s' inode %lld size %zx\n", fil->name,
+		  file_priv->nodeid, file_uc_priv->size);
+	*devp = fil;
+
+	return 0;
+}

drivers/virtio/fs_internal.h

@@ -162,4 +162,20 @@ long virtio_fs_read(struct udevice *dev, u64 nodeid, u64 fh, u64 offset,
 int virtio_fs_setup_dir(struct udevice *fsdev, const char *path,
 			struct udevice **devp);
 
+/**
+ * virtio_fs_setup_file() - Look up and open a file, creating a new device
+ *
+ * Sets up a new open file: performs a lookup for the file within a given
+ * directory, opens it via FUSE, then probes and adds a new 'file' device to
+ * represent the opened file
+ *
+ * @dir: The directory device in which to look for the file
+ * @leaf: The name of the file to open (the leaf name)
+ * @oflags: Open flags to use when opening the file
+ * @devp: On success, returns a pointer to the newly created file device
+ * Return: 0 on success, -ve on error
+ */
+int virtio_fs_setup_file(struct udevice *dir, const char *leaf,
+			 enum dir_open_flags_t flags, struct udevice **devp);
+
 #endif