Quelle  stm32_firewall.c   Sprache: C

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2023, STMicroelectronics - All Rights Reserved
 */

#include <linux/bitfield.h>
#include <linux/bits.h>
#include <linux/bus/stm32_firewall_device.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_platform.h>
#include <linux/platform_device.h>
#include <linux/types.h>
#include <linux/slab.h>

#include "stm32_firewall.h"

/* Corresponds to STM32_FIREWALL_MAX_EXTRA_ARGS + firewall ID */
#define STM32_FIREWALL_MAX_ARGS  (STM32_FIREWALL_MAX_EXTRA_ARGS + 1)

static LIST_HEAD(firewall_controller_list);
static DEFINE_MUTEX(firewall_controller_list_lock);

/* Firewall device API */

int stm32_firewall_get_firewall(struct device_node *np, struct stm32_firewall *firewall,
    unsigned int nb_firewall)
{
 struct stm32_firewall_controller *ctrl;
 struct of_phandle_iterator it;
 unsigned int i, j = 0;
 int err;

 if (!firewall || !nb_firewall)
  return -EINVAL;

 /* Parse property with phandle parsed out */
 of_for_each_phandle(&it, err, np, "access-controllers", "#access-controller-cells", 0) {
  struct of_phandle_args provider_args;
  struct device_node *provider = it.node;
  const char *fw_entry;
  bool match = false;

  if (err) {
   pr_err("Unable to get access-controllers property for node %s\n, err: %d",
          np->full_name, err);
   of_node_put(provider);
   return err;
  }

  if (j >= nb_firewall) {
   pr_err("Too many firewall controllers");
   of_node_put(provider);
   return -EINVAL;
  }

  provider_args.args_count = of_phandle_iterator_args(&it, provider_args.args,
            STM32_FIREWALL_MAX_ARGS);

  /* Check if the parsed phandle corresponds to a registered firewall controller */
  mutex_lock(&firewall_controller_list_lock);
  list_for_each_entry(ctrl, &firewall_controller_list, entry) {
   if (ctrl->dev->of_node->phandle == it.phandle) {
    match = true;
    firewall[j].firewall_ctrl = ctrl;
    break;
   }
  }
  mutex_unlock(&firewall_controller_list_lock);

  if (!match) {
   firewall[j].firewall_ctrl = NULL;
   pr_err("No firewall controller registered for %s\n", np->full_name);
   of_node_put(provider);
   return -ENODEV;
  }

  err = of_property_read_string_index(np, "access-controller-names", j, &fw_entry);
  if (err == 0)
   firewall[j].entry = fw_entry;

  /* Handle the case when there are no arguments given along with the phandle */
  if (provider_args.args_count < 0 ||
      provider_args.args_count > STM32_FIREWALL_MAX_ARGS) {
   of_node_put(provider);
   return -EINVAL;
  } else if (provider_args.args_count == 0) {
   firewall[j].extra_args_size = 0;
   firewall[j].firewall_id = U32_MAX;
   j++;
   continue;
  }

  /* The firewall ID is always the first argument */
  firewall[j].firewall_id = provider_args.args[0];

  /* Extra args start at the second argument */
  for (i = 0; i < provider_args.args_count - 1; i++)
   firewall[j].extra_args[i] = provider_args.args[i + 1];

  /* Remove the firewall ID arg that is not an extra argument */
  firewall[j].extra_args_size = provider_args.args_count - 1;

  j++;
 }

 return 0;
}
EXPORT_SYMBOL_GPL(stm32_firewall_get_firewall);

int stm32_firewall_grant_access(struct stm32_firewall *firewall)
{
 struct stm32_firewall_controller *firewall_controller;

 if (!firewall || firewall->firewall_id == U32_MAX)
  return -EINVAL;

 firewall_controller = firewall->firewall_ctrl;

 if (!firewall_controller)
  return -ENODEV;

 return firewall_controller->grant_access(firewall_controller, firewall->firewall_id);
}
EXPORT_SYMBOL_GPL(stm32_firewall_grant_access);

int stm32_firewall_grant_access_by_id(struct stm32_firewall *firewall, u32 subsystem_id)
{
 struct stm32_firewall_controller *firewall_controller;

 if (!firewall || subsystem_id == U32_MAX || firewall->firewall_id == U32_MAX)
  return -EINVAL;

 firewall_controller = firewall->firewall_ctrl;

 if (!firewall_controller)
  return -ENODEV;

 return firewall_controller->grant_access(firewall_controller, subsystem_id);
}
EXPORT_SYMBOL_GPL(stm32_firewall_grant_access_by_id);

void stm32_firewall_release_access(struct stm32_firewall *firewall)
{
 struct stm32_firewall_controller *firewall_controller;

 if (!firewall || firewall->firewall_id == U32_MAX) {
  pr_debug("Incorrect arguments when releasing a firewall access\n");
  return;
 }

 firewall_controller = firewall->firewall_ctrl;

 if (!firewall_controller) {
  pr_debug("No firewall controller to release\n");
  return;
 }

 firewall_controller->release_access(firewall_controller, firewall->firewall_id);
}
EXPORT_SYMBOL_GPL(stm32_firewall_release_access);

void stm32_firewall_release_access_by_id(struct stm32_firewall *firewall, u32 subsystem_id)
{
 struct stm32_firewall_controller *firewall_controller;

 if (!firewall || subsystem_id == U32_MAX || firewall->firewall_id == U32_MAX) {
  pr_debug("Incorrect arguments when releasing a firewall access");
  return;
 }

 firewall_controller = firewall->firewall_ctrl;

 if (!firewall_controller) {
  pr_debug("No firewall controller to release");
  return;
 }

 firewall_controller->release_access(firewall_controller, subsystem_id);
}
EXPORT_SYMBOL_GPL(stm32_firewall_release_access_by_id);

/* Firewall controller API */

int stm32_firewall_controller_register(struct stm32_firewall_controller *firewall_controller)
{
 struct stm32_firewall_controller *ctrl;

 if (!firewall_controller)
  return -ENODEV;

 pr_info("Registering %s firewall controller\n", firewall_controller->name);

 mutex_lock(&firewall_controller_list_lock);
 list_for_each_entry(ctrl, &firewall_controller_list, entry) {
  if (ctrl == firewall_controller) {
   pr_debug("%s firewall controller already registered\n",
     firewall_controller->name);
   mutex_unlock(&firewall_controller_list_lock);
   return 0;
  }
 }
 list_add_tail(&firewall_controller->entry, &firewall_controller_list);
 mutex_unlock(&firewall_controller_list_lock);

 return 0;
}
EXPORT_SYMBOL_GPL(stm32_firewall_controller_register);

void stm32_firewall_controller_unregister(struct stm32_firewall_controller *firewall_controller)
{
 struct stm32_firewall_controller *ctrl;
 bool controller_removed = false;

 if (!firewall_controller) {
  pr_debug("Null reference while unregistering firewall controller\n");
  return;
 }

 mutex_lock(&firewall_controller_list_lock);
 list_for_each_entry(ctrl, &firewall_controller_list, entry) {
  if (ctrl == firewall_controller) {
   controller_removed = true;
   list_del_init(&ctrl->entry);
   break;
  }
 }
 mutex_unlock(&firewall_controller_list_lock);

 if (!controller_removed)
  pr_debug("There was no firewall controller named %s to unregister\n",
    firewall_controller->name);
}
EXPORT_SYMBOL_GPL(stm32_firewall_controller_unregister);

int stm32_firewall_populate_bus(struct stm32_firewall_controller *firewall_controller)
{
 struct stm32_firewall *firewalls;
 struct device_node *child;
 struct device *parent;
 unsigned int i;
 int len;
 int err;

 parent = firewall_controller->dev;

 dev_dbg(parent, "Populating %s system bus\n", dev_name(firewall_controller->dev));

 for_each_available_child_of_node(dev_of_node(parent), child) {
  /* The access-controllers property is mandatory for firewall bus devices */
  len = of_count_phandle_with_args(child, "access-controllers",
       "#access-controller-cells");
  if (len <= 0) {
   of_node_put(child);
   return -EINVAL;
  }

  firewalls = kcalloc(len, sizeof(*firewalls), GFP_KERNEL);
  if (!firewalls) {
   of_node_put(child);
   return -ENOMEM;
  }

  err = stm32_firewall_get_firewall(child, firewalls, (unsigned int)len);
  if (err) {
   kfree(firewalls);
   of_node_put(child);
   return err;
  }

  for (i = 0; i < len; i++) {
   if (firewall_controller->grant_access(firewall_controller,
             firewalls[i].firewall_id)) {
    /*
 * Peripheral access not allowed or not defined.
 * Mark the node as populated so platform bus won't probe it
 */
    of_detach_node(child);
    dev_err(parent, "%s: Device driver will not be probed\n",
     child->full_name);
   }
  }

  kfree(firewalls);
 }

 return 0;
}
EXPORT_SYMBOL_GPL(stm32_firewall_populate_bus);