// SPDX-License-Identifier: GPL-2.0-only
/*
 * cbmem.c
 *
 * Driver for exporting cbmem entries in sysfs.
 *
 * Copyright 2022 Google LLC
 */

#include <linux/device.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/kobject.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/sysfs.h>

#include "coreboot_table.h"

struct cbmem_entry {
        char *mem_file_buf;
        u32 size;
};

static struct cbmem_entry *to_cbmem_entry(struct kobject *kobj)
{
        return dev_get_drvdata(kobj_to_dev(kobj));
}

static ssize_t mem_read(struct file *filp, struct kobject *kobj,
                        const struct bin_attribute *bin_attr, char *buf, loff_t pos,
                        size_t count)
{
        struct cbmem_entry *entry = to_cbmem_entry(kobj);

        return memory_read_from_buffer(buf, count, &pos, entry->mem_file_buf,
                                       entry->size);
}

static ssize_t mem_write(struct file *filp, struct kobject *kobj,
                         const struct bin_attribute *bin_attr, char *buf, loff_t pos,
                         size_t count)
{
        struct cbmem_entry *entry = to_cbmem_entry(kobj);

        if (pos < 0 || pos >= entry->size)
                return -EINVAL;
        if (count > entry->size - pos)
                count = entry->size - pos;

        memcpy(entry->mem_file_buf + pos, buf, count);
        return count;
}
static const BIN_ATTR_ADMIN_RW(mem, 0);

static ssize_t address_show(struct device *dev, struct device_attribute *attr,
                            char *buf)
{
        struct coreboot_device *cbdev = dev_to_coreboot_device(dev);

        return sysfs_emit(buf, "0x%llx\n", cbdev->cbmem_entry.address);
}
static DEVICE_ATTR_RO(address);

static ssize_t size_show(struct device *dev, struct device_attribute *attr,
                         char *buf)
{
        struct coreboot_device *cbdev = dev_to_coreboot_device(dev);

        return sysfs_emit(buf, "0x%x\n", cbdev->cbmem_entry.entry_size);
}
static DEVICE_ATTR_RO(size);

static struct attribute *attrs[] = {
        &dev_attr_address.attr,
        &dev_attr_size.attr,
        NULL,
};

static const struct bin_attribute *const bin_attrs[] = {
        &bin_attr_mem,
        NULL,
};

static const struct attribute_group cbmem_entry_group = {
        .attrs = attrs,
        .bin_attrs = bin_attrs,
};

static const struct attribute_group *dev_groups[] = {
        &cbmem_entry_group,
        NULL,
};

static int cbmem_entry_probe(struct coreboot_device *dev)
{
        struct cbmem_entry *entry;

        entry = devm_kzalloc(&dev->dev, sizeof(*entry), GFP_KERNEL);
        if (!entry)
                return -ENOMEM;

        dev_set_drvdata(&dev->dev, entry);
        entry->mem_file_buf = devm_memremap(&dev->dev, dev->cbmem_entry.address,
                                            dev->cbmem_entry.entry_size,
                                            MEMREMAP_WB);
        if (IS_ERR(entry->mem_file_buf))
                return PTR_ERR(entry->mem_file_buf);

        entry->size = dev->cbmem_entry.entry_size;

        return 0;
}

static const struct coreboot_device_id cbmem_ids[] = {
        { .tag = LB_TAG_CBMEM_ENTRY },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(coreboot, cbmem_ids);

static struct coreboot_driver cbmem_entry_driver = {
        .probe = cbmem_entry_probe,
        .drv = {
                .name = "cbmem",
                .dev_groups = dev_groups,
        },
        .id_table = cbmem_ids,
};
module_coreboot_driver(cbmem_entry_driver);

MODULE_AUTHOR("Jack Rosenthal <jrosenth@chromium.org>");
MODULE_DESCRIPTION("Driver for exporting CBMEM entries in sysfs");
MODULE_LICENSE("GPL");