debugfs: add 9p device interface

The 9p interface provides abstraction layers allowing the software
that uses devices to be independent from the hardware.

This patch provides a file system abstraction to link drivers to their
devices and propose a common interface to expose driver operations to
higher layers. This file system can be used to access and configure a
device by doing read/write operations.

Signed-off-by: Ambroise Vincent <ambroise.vincent@arm.com>
Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
Change-Id: Ia9662393baf489855dc0c8f389fe4a0afbc9c255

1 files changed, 97 insertions, 0 deletions

diff --git a/lib/debugfs/devroot.c b/lib/debugfs/devroot.c
new file mode 100644
index 000000000..9dd6c92ef
--- /dev/null
+++ b/lib/debugfs/devroot.c
@@ -0,0 +1,97 @@
+/*
+ * Copyright (c) 2019, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <assert.h>
+#include <common/debug.h>
+#include <lib/debugfs.h>
+
+#include "blobs.h"
+#include "dev.h"
+
+/*******************************************************************************
+ * This array contains the directories available from the root directory.
+ ******************************************************************************/
+static const dirtab_t dirtab[] = {
+	{"dev",   CHDIR | DEV_ROOT_QDEV,   0, O_READ},
+	{"blobs", CHDIR | DEV_ROOT_QBLOBS, 0, O_READ},
+	{"fip",   CHDIR | DEV_ROOT_QFIP,   0, O_READ}
+};
+
+static const dirtab_t devfstab[] = {
+};
+
+/*******************************************************************************
+ * This function exposes the elements of the root directory.
+ * It also exposes the content of the dev and blobs directories.
+ ******************************************************************************/
+static int rootgen(chan_t *channel, const dirtab_t *tab, int ntab,
+		   int n, dir_t *dir)
+{
+	switch (channel->qid & ~CHDIR) {
+	case DEV_ROOT_QROOT:
+		tab = dirtab;
+		ntab = NELEM(dirtab);
+		break;
+	case DEV_ROOT_QDEV:
+		tab = devfstab;
+		ntab = NELEM(devfstab);
+		break;
+	case DEV_ROOT_QBLOBS:
+		tab = blobtab;
+		ntab = NELEM(blobtab);
+		break;
+	default:
+		return 0;
+	}
+
+	return devgen(channel, tab, ntab, n, dir);
+}
+
+static int rootwalk(chan_t *channel, const char *name)
+{
+	return devwalk(channel, name, NULL, 0, rootgen);
+}
+
+/*******************************************************************************
+ * This function copies at most n bytes from the element referred by c into buf.
+ ******************************************************************************/
+static int rootread(chan_t *channel, void *buf, int size)
+{
+	const dirtab_t *dp;
+	dir_t *dir;
+
+	if ((channel->qid & CHDIR) != 0) {
+		if (size < sizeof(dir_t)) {
+			return -1;
+		}
+
+		dir = buf;
+		return dirread(channel, dir, NULL, 0, rootgen);
+	}
+
+	/* Only makes sense when using debug language */
+	assert(channel->qid != DEV_ROOT_QBLOBCTL);
+
+	dp = &blobtab[channel->qid - DEV_ROOT_QBLOBCTL];
+	return buf_to_channel(channel, buf, dp->data, size, dp->length);
+}
+
+static int rootstat(chan_t *channel, const char *file, dir_t *dir)
+{
+	return devstat(channel, file, dir, NULL, 0, rootgen);
+}
+
+const dev_t rootdevtab = {
+	.id = '/',
+	.stat = rootstat,
+	.clone = devclone,
+	.attach = devattach,
+	.walk = rootwalk,
+	.read = rootread,
+	.write = deverrwrite,
+	.mount = deverrmount,
+	.seek = devseek
+};