rfkill: create useful userspace interface

The new code added by this patch will make rfkill create
a misc character device /dev/rfkill that userspace can use
to control rfkill soft blocks and get status of devices as
well as events when the status changes.

Using it is very simple -- when you open it you can read
a number of times to get the initial state, and every
further read blocks (you can poll) on getting the next
event from the kernel. The same structure you read is
also used when writing to it to change the soft block of
a given device, all devices of a given type, or all
devices.

This also makes CONFIG_RFKILL_INPUT selectable again in
order to be able to test without it present since its
functionality can now be replaced by userspace entirely
and distros and users may not want the input part of
rfkill interfering with their userspace code. We will
also write a userspace daemon to handle all that and
consequently add the input code to the feature removal
schedule.

In order to have rfkilld support both kernels with and
without CONFIG_RFKILL_INPUT (or new kernels after its
eventual removal) we also add an ioctl (that only exists
if rfkill-input is present) to disable rfkill-input.
It is not very efficient, but at least gives the correct
behaviour in all cases.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

2 files changed, 327 insertions, 7 deletions

diff --git a/net/rfkill/Kconfig b/net/rfkill/Kconfig
index b47f72fae05d..fd7600d8ab14 100644
--- a/net/rfkill/Kconfig
+++ b/net/rfkill/Kconfig
@@ -18,7 +18,7 @@ config RFKILL_LEDS
         default y
 
 config RFKILL_INPUT
-        bool
+        bool "RF switch input support"
         depends on RFKILL
         depends on INPUT = y || RFKILL = INPUT
-        default y
+        default y if !EMBEDDED
diff --git a/net/rfkill/core.c b/net/rfkill/core.c
index 30a6f8d819b2..2230aa6b14f3 100644
--- a/net/rfkill/core.c
+++ b/net/rfkill/core.c
@@ -28,6 +28,10 @@
 #include <linux/mutex.h>
 #include <linux/rfkill.h>
 #include <linux/spinlock.h>
+#include <linux/miscdevice.h>
+#include <linux/wait.h>
+#include <linux/poll.h>
+#include <linux/fs.h>
 
 #include "rfkill.h"
 
@@ -49,6 +53,8 @@ struct rfkill {
 
         unsigned long           state;
 
+        u32                     idx;
+
         bool                    registered;
         bool                    suspended;
 
@@ -69,6 +75,18 @@ struct rfkill {
 };
 #define to_rfkill(d)    container_of(d, struct rfkill, dev)
 
+struct rfkill_int_event {
+        struct list_head        list;
+        struct rfkill_event     ev;
+};
+
+struct rfkill_data {
+        struct list_head        list;
+        struct list_head        events;
+        struct mutex            mtx;
+        wait_queue_head_t       read_wait;
+        bool                    input_handler;
+};
 
 
 MODULE_AUTHOR("Ivo van Doorn <IvDoorn@gmail.com>");
@@ -90,6 +108,7 @@ MODULE_LICENSE("GPL");
  */
 static LIST_HEAD(rfkill_list);  /* list of registered rf switches */
 static DEFINE_MUTEX(rfkill_global_mutex);
+static LIST_HEAD(rfkill_fds);   /* list of open fds of /dev/rfkill */
 
 static unsigned int rfkill_default_state = 1;
 module_param_named(default_state, rfkill_default_state, uint, 0444);
@@ -171,12 +190,48 @@ static inline void rfkill_led_trigger_unregister(struct rfkill *rfkill)
 }
 #endif /* CONFIG_RFKILL_LEDS */
 
-static void rfkill_uevent(struct rfkill *rfkill)
+static void rfkill_fill_event(struct rfkill_event *ev, struct rfkill *rfkill,
+                              enum rfkill_operation op)
+{
+        unsigned long flags;
+
+        ev->idx = rfkill->idx;
+        ev->type = rfkill->type;
+        ev->op = op;
+
+        spin_lock_irqsave(&rfkill->lock, flags);
+        ev->hard = !!(rfkill->state & RFKILL_BLOCK_HW);
+        ev->soft = !!(rfkill->state & (RFKILL_BLOCK_SW |
+                                        RFKILL_BLOCK_SW_PREV));
+        spin_unlock_irqrestore(&rfkill->lock, flags);
+}
+
+static void rfkill_send_events(struct rfkill *rfkill, enum rfkill_operation op)
+{
+        struct rfkill_data *data;
+        struct rfkill_int_event *ev;
+
+        list_for_each_entry(data, &rfkill_fds, list) {
+                ev = kzalloc(sizeof(*ev), GFP_KERNEL);
+                if (!ev)
+                        continue;
+                rfkill_fill_event(&ev->ev, rfkill, op);
+                mutex_lock(&data->mtx);
+                list_add_tail(&ev->list, &data->events);
+                mutex_unlock(&data->mtx);
+                wake_up_interruptible(&data->read_wait);
+        }
+}
+
+static void rfkill_event(struct rfkill *rfkill)
 {
         if (!rfkill->registered || rfkill->suspended)
                 return;
 
         kobject_uevent(&rfkill->dev.kobj, KOBJ_CHANGE);
+
+        /* also send event to /dev/rfkill */
+        rfkill_send_events(rfkill, RFKILL_OP_CHANGE);
 }
 
 static bool __rfkill_set_hw_state(struct rfkill *rfkill,
@@ -260,9 +315,12 @@ static void rfkill_set_block(struct rfkill *rfkill, bool blocked)
         spin_unlock_irqrestore(&rfkill->lock, flags);
 
         rfkill_led_trigger_event(rfkill);
-        rfkill_uevent(rfkill);
+        rfkill_event(rfkill);
 }
 
+#ifdef CONFIG_RFKILL_INPUT
+static atomic_t rfkill_input_disabled = ATOMIC_INIT(0);
+
 /**
  * __rfkill_switch_all - Toggle state of all switches of given type
  * @type: type of interfaces to be affected
@@ -299,6 +357,9 @@ static void __rfkill_switch_all(const enum rfkill_type type, bool blocked)
  */
 void rfkill_switch_all(enum rfkill_type type, bool blocked)
 {
+        if (atomic_read(&rfkill_input_disabled))
+                return;
+
         mutex_lock(&rfkill_global_mutex);
 
         if (!rfkill_epo_lock_active)
@@ -321,6 +382,9 @@ void rfkill_epo(void)
         struct rfkill *rfkill;
         int i;
 
+        if (atomic_read(&rfkill_input_disabled))
+                return;
+
         mutex_lock(&rfkill_global_mutex);
 
         rfkill_epo_lock_active = true;
@@ -331,6 +395,7 @@ void rfkill_epo(void)
                 rfkill_global_states[i].def = rfkill_global_states[i].cur;
                 rfkill_global_states[i].cur = true;
         }
+
         mutex_unlock(&rfkill_global_mutex);
 }
 
@@ -345,6 +410,9 @@ void rfkill_restore_states(void)
 {
         int i;
 
+        if (atomic_read(&rfkill_input_disabled))
+                return;
+
         mutex_lock(&rfkill_global_mutex);
 
         rfkill_epo_lock_active = false;
@@ -361,6 +429,9 @@ void rfkill_restore_states(void)
  */
 void rfkill_remove_epo_lock(void)
 {
+        if (atomic_read(&rfkill_input_disabled))
+                return;
+
         mutex_lock(&rfkill_global_mutex);
         rfkill_epo_lock_active = false;
         mutex_unlock(&rfkill_global_mutex);
@@ -391,9 +462,12 @@ bool rfkill_get_global_sw_state(const enum rfkill_type type)
 {
         return rfkill_global_states[type].cur;
 }
+#endif
 
 void rfkill_set_global_sw_state(const enum rfkill_type type, bool blocked)
 {
+        BUG_ON(type == RFKILL_TYPE_ALL);
+
         mutex_lock(&rfkill_global_mutex);
 
         /* don't allow unblock when epo */
@@ -537,6 +611,15 @@ static ssize_t rfkill_type_show(struct device *dev,
         return sprintf(buf, "%s\n", rfkill_get_type_str(rfkill->type));
 }
 
+static ssize_t rfkill_idx_show(struct device *dev,
+                               struct device_attribute *attr,
+                               char *buf)
+{
+        struct rfkill *rfkill = to_rfkill(dev);
+
+        return sprintf(buf, "%d\n", rfkill->idx);
+}
+
 static u8 user_state_from_blocked(unsigned long state)
 {
         if (state & RFKILL_BLOCK_HW)
@@ -594,6 +677,7 @@ static ssize_t rfkill_claim_store(struct device *dev,
 static struct device_attribute rfkill_dev_attrs[] = {
         __ATTR(name, S_IRUGO, rfkill_name_show, NULL),
         __ATTR(type, S_IRUGO, rfkill_type_show, NULL),
+        __ATTR(index, S_IRUGO, rfkill_idx_show, NULL),
         __ATTR(state, S_IRUGO|S_IWUSR, rfkill_state_show, rfkill_state_store),
         __ATTR(claim, S_IRUGO|S_IWUSR, rfkill_claim_show, rfkill_claim_store),
         __ATTR_NULL
@@ -708,7 +792,7 @@ struct rfkill * __must_check rfkill_alloc(const char *name,
         if (WARN_ON(!name))
                 return NULL;
 
-        if (WARN_ON(type >= NUM_RFKILL_TYPES))
+        if (WARN_ON(type == RFKILL_TYPE_ALL || type >= NUM_RFKILL_TYPES))
                 return NULL;
 
         rfkill = kzalloc(sizeof(*rfkill), GFP_KERNEL);
@@ -754,7 +838,9 @@ static void rfkill_uevent_work(struct work_struct *work)
 
         rfkill = container_of(work, struct rfkill, uevent_work);
 
-        rfkill_uevent(rfkill);
+        mutex_lock(&rfkill_global_mutex);
+        rfkill_event(rfkill);
+        mutex_unlock(&rfkill_global_mutex);
 }
 
 static void rfkill_sync_work(struct work_struct *work)
@@ -785,6 +871,7 @@ int __must_check rfkill_register(struct rfkill *rfkill)
                 goto unlock;
         }
 
+        rfkill->idx = rfkill_no;
         dev_set_name(dev, "rfkill%lu", rfkill_no);
         rfkill_no++;
 
@@ -819,6 +906,7 @@ int __must_check rfkill_register(struct rfkill *rfkill)
 
         INIT_WORK(&rfkill->sync_work, rfkill_sync_work);
         schedule_work(&rfkill->sync_work);
+        rfkill_send_events(rfkill, RFKILL_OP_ADD);
 
         mutex_unlock(&rfkill_global_mutex);
         return 0;
@@ -848,6 +936,7 @@ void rfkill_unregister(struct rfkill *rfkill)
         device_del(&rfkill->dev);
 
         mutex_lock(&rfkill_global_mutex);
+        rfkill_send_events(rfkill, RFKILL_OP_DEL);
         list_del_init(&rfkill->node);
         mutex_unlock(&rfkill_global_mutex);
 
@@ -862,6 +951,227 @@ void rfkill_destroy(struct rfkill *rfkill)
 }
 EXPORT_SYMBOL(rfkill_destroy);
 
+static int rfkill_fop_open(struct inode *inode, struct file *file)
+{
+        struct rfkill_data *data;
+        struct rfkill *rfkill;
+        struct rfkill_int_event *ev, *tmp;
+
+        data = kzalloc(sizeof(*data), GFP_KERNEL);
+        if (!data)
+                return -ENOMEM;
+
+        INIT_LIST_HEAD(&data->events);
+        mutex_init(&data->mtx);
+        init_waitqueue_head(&data->read_wait);
+
+        mutex_lock(&rfkill_global_mutex);
+        mutex_lock(&data->mtx);
+        /*
+         * start getting events from elsewhere but hold mtx to get
+         * startup events added first
+         */
+        list_add(&data->list, &rfkill_fds);
+
+        list_for_each_entry(rfkill, &rfkill_list, node) {
+                ev = kzalloc(sizeof(*ev), GFP_KERNEL);
+                if (!ev)
+                        goto free;
+                rfkill_fill_event(&ev->ev, rfkill, RFKILL_OP_ADD);
+                list_add_tail(&ev->list, &data->events);
+        }
+        mutex_unlock(&data->mtx);
+        mutex_unlock(&rfkill_global_mutex);
+
+        file->private_data = data;
+
+        return nonseekable_open(inode, file);
+
+ free:
+        mutex_unlock(&data->mtx);
+        mutex_unlock(&rfkill_global_mutex);
+        mutex_destroy(&data->mtx);
+        list_for_each_entry_safe(ev, tmp, &data->events, list)
+                kfree(ev);
+        kfree(data);
+        return -ENOMEM;
+}
+
+static unsigned int rfkill_fop_poll(struct file *file, poll_table *wait)
+{
+        struct rfkill_data *data = file->private_data;
+        unsigned int res = POLLOUT | POLLWRNORM;
+
+        poll_wait(file, &data->read_wait, wait);
+
+        mutex_lock(&data->mtx);
+        if (!list_empty(&data->events))
+                res = POLLIN | POLLRDNORM;
+        mutex_unlock(&data->mtx);
+
+        return res;
+}
+
+static bool rfkill_readable(struct rfkill_data *data)
+{
+        bool r;
+
+        mutex_lock(&data->mtx);
+        r = !list_empty(&data->events);
+        mutex_unlock(&data->mtx);
+
+        return r;
+}
+
+static ssize_t rfkill_fop_read(struct file *file, char __user *buf,
+                               size_t count, loff_t *pos)
+{
+        struct rfkill_data *data = file->private_data;
+        struct rfkill_int_event *ev;
+        unsigned long sz;
+        int ret;
+
+        mutex_lock(&data->mtx);
+
+        while (list_empty(&data->events)) {
+                if (file->f_flags & O_NONBLOCK) {
+                        ret = -EAGAIN;
+                        goto out;
+                }
+                mutex_unlock(&data->mtx);
+                ret = wait_event_interruptible(data->read_wait,
+                                               rfkill_readable(data));
+                mutex_lock(&data->mtx);
+
+                if (ret)
+                        goto out;
+        }
+
+        ev = list_first_entry(&data->events, struct rfkill_int_event,
+                                list);
+
+        sz = min_t(unsigned long, sizeof(ev->ev), count);
+        ret = sz;
+        if (copy_to_user(buf, &ev->ev, sz))
+                ret = -EFAULT;
+
+        list_del(&ev->list);
+        kfree(ev);
+ out:
+        mutex_unlock(&data->mtx);
+        return ret;
+}
+
+static ssize_t rfkill_fop_write(struct file *file, const char __user *buf,
+                                size_t count, loff_t *pos)
+{
+        struct rfkill *rfkill;
+        struct rfkill_event ev;
+
+        /* we don't need the 'hard' variable but accept it */
+        if (count < sizeof(ev) - 1)
+                return -EINVAL;
+
+        if (copy_from_user(&ev, buf, sizeof(ev) - 1))
+                return -EFAULT;
+
+        if (ev.op != RFKILL_OP_CHANGE && ev.op != RFKILL_OP_CHANGE_ALL)
+                return -EINVAL;
+
+        if (ev.type >= NUM_RFKILL_TYPES)
+                return -EINVAL;
+
+        mutex_lock(&rfkill_global_mutex);
+
+        if (ev.op == RFKILL_OP_CHANGE_ALL) {
+                if (ev.type == RFKILL_TYPE_ALL) {
+                        enum rfkill_type i;
+                        for (i = 0; i < NUM_RFKILL_TYPES; i++)
+                                rfkill_global_states[i].cur = ev.soft;
+                } else {
+                        rfkill_global_states[ev.type].cur = ev.soft;
+                }
+        }
+
+        list_for_each_entry(rfkill, &rfkill_list, node) {
+                if (rfkill->idx != ev.idx && ev.op != RFKILL_OP_CHANGE_ALL)
+                        continue;
+
+                if (rfkill->type != ev.type && ev.type != RFKILL_TYPE_ALL)
+                        continue;
+
+                rfkill_set_block(rfkill, ev.soft);
+        }
+        mutex_unlock(&rfkill_global_mutex);
+
+        return count;
+}
+
+static int rfkill_fop_release(struct inode *inode, struct file *file)
+{
+        struct rfkill_data *data = file->private_data;
+        struct rfkill_int_event *ev, *tmp;
+
+        mutex_lock(&rfkill_global_mutex);
+        list_del(&data->list);
+        mutex_unlock(&rfkill_global_mutex);
+
+        mutex_destroy(&data->mtx);
+        list_for_each_entry_safe(ev, tmp, &data->events, list)
+                kfree(ev);
+
+#ifdef CONFIG_RFKILL_INPUT
+        if (data->input_handler)
+                atomic_dec(&rfkill_input_disabled);
+#endif
+
+        kfree(data);
+
+        return 0;
+}
+
+#ifdef CONFIG_RFKILL_INPUT
+static long rfkill_fop_ioctl(struct file *file, unsigned int cmd,
+                             unsigned long arg)
+{
+        struct rfkill_data *data = file->private_data;
+
+        if (_IOC_TYPE(cmd) != RFKILL_IOC_MAGIC)
+                return -ENOSYS;
+
+        if (_IOC_NR(cmd) != RFKILL_IOC_NOINPUT)
+                return -ENOSYS;
+
+        mutex_lock(&data->mtx);
+
+        if (!data->input_handler) {
+                atomic_inc(&rfkill_input_disabled);
+                data->input_handler = true;
+        }
+
+        mutex_unlock(&data->mtx);
+
+        return 0;
+}
+#endif
+
+static const struct file_operations rfkill_fops = {
+        .open           = rfkill_fop_open,
+        .read           = rfkill_fop_read,
+        .write          = rfkill_fop_write,
+        .poll           = rfkill_fop_poll,
+        .release        = rfkill_fop_release,
+#ifdef CONFIG_RFKILL_INPUT
+        .unlocked_ioctl = rfkill_fop_ioctl,
+        .compat_ioctl   = rfkill_fop_ioctl,
+#endif
+};
+
+static struct miscdevice rfkill_miscdev = {
+        .name   = "rfkill",
+        .fops   = &rfkill_fops,
+        .minor  = MISC_DYNAMIC_MINOR,
+};
 
 static int __init rfkill_init(void)
 {
@@ -875,10 +1185,19 @@ static int __init rfkill_init(void)
         if (error)
                 goto out;
 
+        error = misc_register(&rfkill_miscdev);
+        if (error) {
+                class_unregister(&rfkill_class);
+                goto out;
+        }
+
 #ifdef CONFIG_RFKILL_INPUT
         error = rfkill_handler_init();
-        if (error)
+        if (error) {
+                misc_deregister(&rfkill_miscdev);
                 class_unregister(&rfkill_class);
+                goto out;
+        }
 #endif
 
  out:
@@ -891,6 +1210,7 @@ static void __exit rfkill_exit(void)
 #ifdef CONFIG_RFKILL_INPUT
         rfkill_handler_exit();
 #endif
+        misc_deregister(&rfkill_miscdev);
         class_unregister(&rfkill_class);
 }
 module_exit(rfkill_exit);