state: Refactor state framework

The state framework grew organically over the time. Unfortunately the
architecture and abstractions disappeared during this period.

This patch refactors the framework to recreate the abstractions. The
main focus was the backend with its storage. The main use-case was to
offer better NAND support with less erase cycles and interchangeable
data formats (dtb,raw).

The general architecture now has a backend which consists of a data
format and storage. The storage consists of multiple storage buckets
each holding exactly one copy of the state data. A data format describes
a data serialization for the state framework. This can be either dtb or
raw. A storage bucket is a storage location which is used to store any
data. There is a (new) circular type which writes changes behind the
last written data and therefore reduces the number of erases. The other
type is a direct bucket which writes directly to a storage offset for
all non-erase storage.

Furthermore this patch splits up all classes into different files in a
subdirectory.

This is currently all in one patch as I can't see a good way to split
the changes up without having a non-working state framework in between.

The following diagram shows the new architecture roughly:

           .----------.
           |  state   |
           '----------'
                 |
                 |
                 v
  .----------------------------.
  |       state_backend        |
  |----------------------------|
  | + state_load(*state);      |
  | + state_save(*state);      |
  | + state_backend_init(...); |
  |                            |
  |                            |
  '----------------------------'
    |            |                   The format describes
    |            |                   how the state data
    |            '------------->     is serialized
    |   .--------------------------------------------.
    |   |      state_backend_format <INTERFACE>      |
    |   |--------------------------------------------|
    |   | + verify(*format, magic, *buf, len);       |
    |   | + pack(*format, *state, **buf, len);       |
    |   | + unpack(*format, *state, *buf, len);      |
    |   | + get_packed_len(*format, *state);         |
    |   | + free(*format);                           |
    |   '--------------------------------------------'
    |              ^                      ^
    |              *                      *
    |              *                      *
    |   .--------------------. .--------------------.
    |   | backend_format_dtb | | backend_format_raw |
    |   '--------------------' '--------------------'
    |
    |
    |
    v
.----------------------------------------------------------.
|                  state_backend_storage                   |
|----------------------------------------------------------|
| + init(...);                                             |
| + free(*storage);                                        |
| + read(*storage, *format, magic, **buf, *len, len_hint); |
| + write(*storage, *buf, len);                            |
| + restore_consistency(*storage, *buf, len);              |
'----------------------------------------------------------'
                              |
     The backend storage is responsible to manage multiple
     data copies and distribute them onto several buckets.
     Read data is verified against the given format to
     ensure that the read data is correct.
                              |
                              |
                              |
                              |
                              |
                              v
        .------------------------------------------.
        | state_backend_storage_bucket <INTERFACE> |
        |------------------------------------------|
        | + init(*bucket);                         |
        | + write(*bucket, *buf, len);             |
        | + read(*bucket, **buf, len_hint);        |
        | + free(*bucket);                         |
        '------------------------------------------'
                      ^     ^      ^
                     *      *       *
                    *       *        *
 A storage bucket represents*exactly one data copy at one
 data location. A circular b*cket writes any new data to
 the end of the bucket (for *educed erases on NAND). A
 direct bucket directly writ*s at one location.
               *            *             *
              *             *              *
             *              *               *
 .-----------------------.  *  .-------------------------.
 | backend_bucket_direct |  *  | backend_bucket_circular |
 '-----------------------'  *  '-------------------------'
             ^              *               ^
             |              *               |
             |              *               |
             |              *               |
             |  .-----------------------.   |
             '--| backend_bucket_cached |---'
                '-----------------------'
             A backend_bucket_cached is a transparent
             bucket that directly uses another bucket
             as backend device and caches all accesses.

Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 188 insertions, 0 deletions

diff --git a/common/state/backend.c b/common/state/backend.c
new file mode 100644
index 0000000000..2f2e6dfd32
--- /dev/null
+++ b/common/state/backend.c
@@ -0,0 +1,188 @@
+/*
+ * Copyright (C) 2016 Pengutronix, Markus Pargmann <mpa@pengutronix.de>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/string.h>
+#include <malloc.h>
+#include <printk.h>
+
+#include "state.h"
+
+
+/**
+ * Save the state
+ * @param state
+ * @return
+ */
+int state_save(struct state *state)
+{
+	uint8_t *buf;
+	ssize_t len;
+	int ret;
+	struct state_backend *backend = &state->backend;
+
+	if (!state->dirty)
+		return 0;
+
+	ret = backend->format->pack(backend->format, state, &buf, &len);
+	if (ret) {
+		dev_err(&state->dev, "Failed to pack state with backend format %s, %d\n",
+			backend->format->name, ret);
+		return ret;
+	}
+
+	ret = state_storage_write(&backend->storage, buf, len);
+	if (ret) {
+		dev_err(&state->dev, "Failed to write packed state, %d\n", ret);
+		goto out;
+	}
+
+	state->dirty = 0;
+
+out:
+	free(buf);
+	return ret;
+}
+
+/**
+ * state_load - Loads a state from the backend
+ * @param state The state that should be updated to contain the loaded data
+ * @return 0 on success, -errno on failure. If no state is loaded the previous
+ * values remain in the state.
+ *
+ * This function uses the registered storage backend to read data. All data that
+ * we read is checked for integrity by the formatter. After that we unpack the
+ * data into our state.
+ */
+int state_load(struct state *state)
+{
+	uint8_t *buf;
+	ssize_t len;
+	ssize_t len_hint = 0;
+	int ret;
+	struct state_backend *backend = &state->backend;
+
+	if (backend->format->get_packed_len)
+		len_hint = backend->format->get_packed_len(backend->format,
+							   state);
+	ret = state_storage_read(&backend->storage, backend->format,
+				 state->magic, &buf, &len, len_hint);
+	if (ret) {
+		dev_err(&state->dev, "Failed to read state with format %s, %d\n",
+			backend->format->name, ret);
+		return ret;
+	}
+
+	ret = backend->format->unpack(backend->format, state, buf, len);
+	if (ret) {
+		dev_err(&state->dev, "Failed to unpack read data with format %s although verified, %d\n",
+			backend->format->name, ret);
+		goto out;
+	}
+
+	state->dirty = 0;
+
+out:
+	free(buf);
+	return ret;
+}
+
+static int state_format_init(struct state_backend *backend,
+			     struct device_d *dev, const char *backend_format,
+			     struct device_node *node, const char *state_name)
+{
+	int ret;
+
+	if (!strcmp(backend_format, "raw")) {
+		ret = backend_format_raw_create(&backend->format, node,
+						state_name, dev);
+	} else if (!strcmp(backend_format, "dtb")) {
+		ret = backend_format_dtb_create(&backend->format, dev);
+	} else {
+		dev_err(dev, "Invalid backend format %s\n",
+			backend_format);
+		return -EINVAL;
+	}
+
+	if (ret && ret != -EPROBE_DEFER)
+		dev_err(dev, "Failed to initialize format %s, %d\n",
+			backend_format, ret);
+
+	return ret;
+}
+
+static void state_format_free(struct state_backend_format *format)
+{
+	if (format->free)
+		format->free(format);
+}
+
+/**
+ * state_backend_init - Initiates the backend storage and format using the
+ * passed arguments
+ * @param backend state backend
+ * @param dev Device pointer used for prints
+ * @param node the DT device node corresponding to the state
+ * @param backend_format a string describing the format. Valid values are 'raw'
+ * and 'dtb' currently
+ * @param storage_path Path to the backend storage file/device/partition/...
+ * @param state_name Name of the state
+ * @param of_path Path in the devicetree
+ * @param stridesize stridesize in case we have a medium without eraseblocks.
+ * stridesize describes how far apart copies of the same data should be stored.
+ * For blockdevices it makes sense to align them on blocksize.
+ * @param storagetype Type of the storage backend. This may be NULL where we
+ * autoselect some backwardscompatible backend options
+ * @return 0 on success, -errno otherwise
+ */
+int state_backend_init(struct state_backend *backend, struct device_d *dev,
+		       struct device_node *node, const char *backend_format,
+		       const char *storage_path, const char *state_name, const
+		       char *of_path, off_t offset, size_t max_size,
+		       uint32_t stridesize, const char *storagetype)
+{
+	int ret;
+
+	ret = state_format_init(backend, dev, backend_format, node, state_name);
+	if (ret)
+		return ret;
+
+	ret = state_storage_init(&backend->storage, dev, storage_path, offset,
+				 max_size, stridesize, storagetype);
+	if (ret)
+		goto out_free_format;
+
+	backend->of_path = of_path;
+
+	return 0;
+
+out_free_format:
+	state_format_free(backend->format);
+	backend->format = NULL;
+
+	return ret;
+}
+
+void state_backend_set_readonly(struct state_backend *backend)
+{
+	state_storage_set_readonly(&backend->storage);
+}
+
+void state_backend_free(struct state_backend *backend)
+{
+	state_storage_free(&backend->storage);
+	if (backend->format)
+		state_format_free(backend->format);
+}