Re: [PATCH 8/9] rfkill: Userspace control for airplane mode

[João Paulo Rechi Vita]

On 18 February 2016 at 15:12, Johannes Berg  wrote:
> Hi,
>
> Sorry for the delay reviewing this.
>

No problems!

>
> On Mon, 2016-02-08 at 10:41 -0500, João Paulo Rechi Vita wrote:
>> Provide an interface for the airplane-mode indicator be controlled
>> from
>> userspace. User has to first acquire the control through
>> RFKILL_OP_AIRPLANE_MODE_ACQUIRE and keep the fd open for the whole
>> time
>> it wants to be in control of the indicator. Closing the fd or using
>> RFKILL_OP_AIRPLANE_MODE_RELEASE restores the default policy.
>
> I've come to the conclusion that the new ops are probably the best
> thing to do here.
>

Nice.

>> +Userspace can also override the default airplane-mode indicator
>> policy through
>> +/dev/rfkill. Control of the airplane mode indicator has to be
>> acquired first,
>> +using RFKILL_OP_AIRPLANE_MODE_ACQUIRE, and is only available for one
>> userspace
>> +application at a time. Closing the fd or using
>> RFKILL_OP_AIRPLANE_MODE_RELEASE
>> +reverts the airplane-mode indicator back to the default kernel
>> policy and makes
>> +it available for other applications to take control. Changes to the
>> +airplane-mode indicator state can be made using
>> RFKILL_OP_AIRPLANE_MODE_CHANGE,
>> +passing the new value in the 'soft' field of 'struct rfkill_event'.
>
> I don't really see any value in _RELEASE, since an application can just
> close the fd? I'd prefer not having the duplicate functionality
> and force us to exercise the single code path every time.
>

I actually added this op only for completion, I couldn't think of a
use-case where simply closing the fd wouldn't be enough. I'll remove
it for the next revision.

>>  For further details consult Documentation/ABI/stable/sysfs-class-
>> rfkill.
>> diff --git a/include/uapi/linux/rfkill.h
>> b/include/uapi/linux/rfkill.h
>> index 2e00dce..9cb999b 100644
>> --- a/include/uapi/linux/rfkill.h
>> +++ b/include/uapi/linux/rfkill.h
>> @@ -67,6 +67,9 @@ enum rfkill_operation {
>>   RFKILL_OP_DEL,
>>   RFKILL_OP_CHANGE,
>>   RFKILL_OP_CHANGE_ALL,
>> + RFKILL_OP_AIRPLANE_MODE_ACQUIRE,
>> + RFKILL_OP_AIRPLANE_MODE_RELEASE,
>> + RFKILL_OP_AIRPLANE_MODE_CHANGE,
>>  };
>
>> @@ -1199,7 +1202,7 @@ static ssize_t rfkill_fop_write(struct file
>> *file, const char __user *buf,
>>   if (copy_from_user(, buf, count))
>>   return -EFAULT;
>>
>> - if (ev.op != RFKILL_OP_CHANGE && ev.op !=
>> RFKILL_OP_CHANGE_ALL)
>> + if (ev.op < RFKILL_OP_CHANGE)
>>   return -EINVAL;
>
> You need to also reject invalid high values, like 27.
>

Yes, sorry for missing this.

>>   mutex_lock(_global_mutex);
>>
>> + if (ev.op == RFKILL_OP_AIRPLANE_MODE_ACQUIRE) {
>> + if (rfkill_apm_owned && !data->is_apm_owner) {
>> + count = -EACCES;
>> + } else {
>> + rfkill_apm_owned = true;
>> + data->is_apm_owner = true;
>> + }
>> + }
>> +
>> + if (ev.op == RFKILL_OP_AIRPLANE_MODE_RELEASE) {
>
> It would probably be better to simply use "switch (ev.op)" and make the
> default case do a reject.
>

Sounds better indeed.

>>   if (ev.op == RFKILL_OP_CHANGE_ALL)
>>   rfkill_update_global_state(ev.type, ev.soft);
>
> Also moving the existing code inside the switch, of course.
>

Sure.

--
João Paulo Rechi Vita
http://about.me/jprvita

Re: [PATCH 8/9] rfkill: Userspace control for airplane mode

[Johannes Berg]

Hi,

Sorry for the delay reviewing this.



On Mon, 2016-02-08 at 10:41 -0500, João Paulo Rechi Vita wrote:
> Provide an interface for the airplane-mode indicator be controlled
> from
> userspace. User has to first acquire the control through
> RFKILL_OP_AIRPLANE_MODE_ACQUIRE and keep the fd open for the whole
> time
> it wants to be in control of the indicator. Closing the fd or using
> RFKILL_OP_AIRPLANE_MODE_RELEASE restores the default policy.

I've come to the conclusion that the new ops are probably the best
thing to do here.

> +Userspace can also override the default airplane-mode indicator
> policy through
> +/dev/rfkill. Control of the airplane mode indicator has to be
> acquired first,
> +using RFKILL_OP_AIRPLANE_MODE_ACQUIRE, and is only available for one
> userspace
> +application at a time. Closing the fd or using
> RFKILL_OP_AIRPLANE_MODE_RELEASE
> +reverts the airplane-mode indicator back to the default kernel
> policy and makes
> +it available for other applications to take control. Changes to the
> +airplane-mode indicator state can be made using
> RFKILL_OP_AIRPLANE_MODE_CHANGE,
> +passing the new value in the 'soft' field of 'struct rfkill_event'.

I don't really see any value in _RELEASE, since an application can just
close the fd? I'd prefer not having the duplicate functionality
and force us to exercise the single code path every time.

>  For further details consult Documentation/ABI/stable/sysfs-class-
> rfkill.
> diff --git a/include/uapi/linux/rfkill.h
> b/include/uapi/linux/rfkill.h
> index 2e00dce..9cb999b 100644
> --- a/include/uapi/linux/rfkill.h
> +++ b/include/uapi/linux/rfkill.h
> @@ -67,6 +67,9 @@ enum rfkill_operation {
>   RFKILL_OP_DEL,
>   RFKILL_OP_CHANGE,
>   RFKILL_OP_CHANGE_ALL,
> + RFKILL_OP_AIRPLANE_MODE_ACQUIRE,
> + RFKILL_OP_AIRPLANE_MODE_RELEASE,
> + RFKILL_OP_AIRPLANE_MODE_CHANGE,
>  };
 
> @@ -1199,7 +1202,7 @@ static ssize_t rfkill_fop_write(struct file
> *file, const char __user *buf,
>   if (copy_from_user(, buf, count))
>   return -EFAULT;
>  
> - if (ev.op != RFKILL_OP_CHANGE && ev.op !=
> RFKILL_OP_CHANGE_ALL)
> + if (ev.op < RFKILL_OP_CHANGE)
>   return -EINVAL;

You need to also reject invalid high values, like 27.

>   mutex_lock(_global_mutex);
>  
> + if (ev.op == RFKILL_OP_AIRPLANE_MODE_ACQUIRE) {
> + if (rfkill_apm_owned && !data->is_apm_owner) {
> + count = -EACCES;
> + } else {
> + rfkill_apm_owned = true;
> + data->is_apm_owner = true;
> + }
> + }
> +
> + if (ev.op == RFKILL_OP_AIRPLANE_MODE_RELEASE) {

It would probably be better to simply use "switch (ev.op)" and make the
default case do a reject.

>   if (ev.op == RFKILL_OP_CHANGE_ALL)
>   rfkill_update_global_state(ev.type, ev.soft);

Also moving the existing code inside the switch, of course.

johannes

Re: [PATCH 8/9] rfkill: Userspace control for airplane mode

[João Paulo Rechi Vita]

On 10 February 2016 at 12:12, Johannes Berg  wrote:
> On 2016-02-10 17:53, Dan Williams wrote:
>>
>> Yeah, I get that now.  It's just that to me, something called
>> "AIRPLANE_MODE_CHANGE" seems like it should actually change airplane
>> mode on/off, which implies killing radios.  I wouldn't have had the
>> problem if it was named AIRPLANE_MODE_INDICATOR_CHANGE, which makes it
>> clear this is simply an indicator and has no actual effect on anything
>> other than a LED.
>

I also agree the AIRPLANE_MODE_INDICATOR_* prefix makes things more
clear here. Thanks for the feedback, Dan!

>
> Yeah, I agree. I'm not even sure that it's a good idea to subsume this into
> the regular operations in the API, although that's obviously the easiest
> extension. I'll need to think about that a bit more with the code at hand
> though.
>

Initially I have thought about creating and additional RFKill switch
for that, but I think it would be a bit hackish since we would have to
treat it specially in sysfs attributes and probably other places, and
userspace would also need a special case when going through the list
of RFKill switches in the system. The proposed solution has equivalent
semantics to an RFKill switch, is backward-compatible (users would
only ignore the unknown operations and evens -- although gsd has a
"default:" case to abort execution on an unknown event) and does not
extend the RFKill event struct.

One alternative would be to move the control point to a separate
device, like /dev/rfkill-airplane-mode, but I'm not sure this is a
very elegant approach. Anyway, I'm open to work on changes to the API,
but it would be great if you could at least pick or reject the
non-polemical patches of the series, so I don't need to carry them
anymore.

--
João Paulo Rechi Vita
http://about.me/jprvita

Re: [PATCH 8/9] rfkill: Userspace control for airplane mode

[Dan Williams]

On Wed, 2016-02-10 at 17:07 +0100, Johannes Berg wrote:
> On Mon, 2016-02-08 at 10:11 -0600, Dan Williams wrote:
> > I'd like to clarify a bit, so tell me if I'm correct or not.  Using
> > RFKILL_OP_AIRPLANE_MODE_CHANGE does not actually change any device
> > state. It's just an indicator with no relationship to any of the
> > registered rfkill switches, right?
> 
> Yes. I'm not sure I'm totally happy with this userspace API.
> 
> > I wonder if setting RFKILL_OP_AIRPLANE_MODE_CHANGE(true) shouldn't
> > also
> > softblock all switches, otherwise you can set airplane mode all day
> > long with RFKILL_OP_AIRPLANE_MODE_CHANGE and it doesn't actually
> > enable
> > airplane mode at all?
> 
> No, this is kinda the point that you could implement your policy in
> userspace now.

Yeah, I get that now.  It's just that to me, something called
"AIRPLANE_MODE_CHANGE" seems like it should actually change airplane
mode on/off, which implies killing radios.  I wouldn't have had the
problem if it was named AIRPLANE_MODE_INDICATOR_CHANGE, which makes it
clear this is simply an indicator and has no actual effect on anything
other than a LED.

Dan

Re: [PATCH 8/9] rfkill: Userspace control for airplane mode

[Johannes Berg]

On 2016-02-10 17:53, Dan Williams wrote:

Yeah, I get that now.  It's just that to me, something called
"AIRPLANE_MODE_CHANGE" seems like it should actually change airplane
mode on/off, which implies killing radios.  I wouldn't have had the
problem if it was named AIRPLANE_MODE_INDICATOR_CHANGE, which makes it
clear this is simply an indicator and has no actual effect on anything
other than a LED.


Yeah, I agree. I'm not even sure that it's a good idea to subsume this 
into the regular operations in the API, although that's obviously the 
easiest extension. I'll need to think about that a bit more with the 
code at hand though.


johannes

Re: [PATCH 8/9] rfkill: Userspace control for airplane mode

[Johannes Berg]

On Mon, 2016-02-08 at 10:11 -0600, Dan Williams wrote:
> I'd like to clarify a bit, so tell me if I'm correct or not.  Using
> RFKILL_OP_AIRPLANE_MODE_CHANGE does not actually change any device
> state. It's just an indicator with no relationship to any of the
> registered rfkill switches, right?

Yes. I'm not sure I'm totally happy with this userspace API.

> I wonder if setting RFKILL_OP_AIRPLANE_MODE_CHANGE(true) shouldn't
> also
> softblock all switches, otherwise you can set airplane mode all day
> long with RFKILL_OP_AIRPLANE_MODE_CHANGE and it doesn't actually
> enable
> airplane mode at all?

No, this is kinda the point that you could implement your policy in
userspace now.

johannes

[PATCH 8/9] rfkill: Userspace control for airplane mode

[João Paulo Rechi Vita]

Provide an interface for the airplane-mode indicator be controlled from
userspace. User has to first acquire the control through
RFKILL_OP_AIRPLANE_MODE_ACQUIRE and keep the fd open for the whole time
it wants to be in control of the indicator. Closing the fd or using
RFKILL_OP_AIRPLANE_MODE_RELEASE restores the default policy.

To change state of the indicator, the RFKILL_OP_AIRPLANE_MODE_CHANGE
operation is used, passing the value on "struct rfkill_event.soft". If
the caller has not acquired the airplane-mode control beforehand, the
operation fails.

Signed-off-by: João Paulo Rechi Vita 
---
 Documentation/rfkill.txt| 10 ++
 include/uapi/linux/rfkill.h |  3 +++
 net/rfkill/core.c   | 45 +
 3 files changed, 54 insertions(+), 4 deletions(-)

diff --git a/Documentation/rfkill.txt b/Documentation/rfkill.txt
index b13025a..aa6e014 100644
--- a/Documentation/rfkill.txt
+++ b/Documentation/rfkill.txt
@@ -87,6 +87,7 @@ RFKill provides per-switch LED triggers, which can be used to 
drive LEDs
 according to the switch state (LED_FULL when blocked, LED_OFF otherwise).
 An airplane-mode indicator LED trigger is also available, which triggers
 LED_FULL when all radios known by RFKill are blocked, and LED_OFF otherwise.
+The airplane-mode indicator LED trigger policy can be overridden by userspace.
 
 
 5. Userspace support
@@ -123,5 +124,14 @@ RFKILL_TYPE
 The contents of these variables corresponds to the "name", "state" and
 "type" sysfs files explained above.
 
+Userspace can also override the default airplane-mode indicator policy through
+/dev/rfkill. Control of the airplane mode indicator has to be acquired first,
+using RFKILL_OP_AIRPLANE_MODE_ACQUIRE, and is only available for one userspace
+application at a time. Closing the fd or using RFKILL_OP_AIRPLANE_MODE_RELEASE
+reverts the airplane-mode indicator back to the default kernel policy and makes
+it available for other applications to take control. Changes to the
+airplane-mode indicator state can be made using RFKILL_OP_AIRPLANE_MODE_CHANGE,
+passing the new value in the 'soft' field of 'struct rfkill_event'.
+
 
 For further details consult Documentation/ABI/stable/sysfs-class-rfkill.
diff --git a/include/uapi/linux/rfkill.h b/include/uapi/linux/rfkill.h
index 2e00dce..9cb999b 100644
--- a/include/uapi/linux/rfkill.h
+++ b/include/uapi/linux/rfkill.h
@@ -67,6 +67,9 @@ enum rfkill_operation {
RFKILL_OP_DEL,
RFKILL_OP_CHANGE,
RFKILL_OP_CHANGE_ALL,
+   RFKILL_OP_AIRPLANE_MODE_ACQUIRE,
+   RFKILL_OP_AIRPLANE_MODE_RELEASE,
+   RFKILL_OP_AIRPLANE_MODE_CHANGE,
 };
 
 /**
diff --git a/net/rfkill/core.c b/net/rfkill/core.c
index fb11547..c0da716 100644
--- a/net/rfkill/core.c
+++ b/net/rfkill/core.c
@@ -89,6 +89,7 @@ struct rfkill_data {
struct mutexmtx;
wait_queue_head_t   read_wait;
boolinput_handler;
+   boolis_apm_owner;
 };
 
 
@@ -123,7 +124,7 @@ static struct {
 } rfkill_global_states[NUM_RFKILL_TYPES];
 
 static bool rfkill_epo_lock_active;
-
+static bool rfkill_apm_owned;
 
 #ifdef CONFIG_RFKILL_LEDS
 static struct led_trigger rfkill_apm_led_trigger;
@@ -350,7 +351,8 @@ static void rfkill_update_global_state(enum rfkill_type 
type, bool blocked)
 
for (i = 0; i < NUM_RFKILL_TYPES; i++)
rfkill_global_states[i].cur = blocked;
-   rfkill_apm_led_trigger_event(blocked);
+   if (!rfkill_apm_owned)
+   rfkill_apm_led_trigger_event(blocked);
 }
 
 #ifdef CONFIG_RFKILL_INPUT
@@ -1180,11 +1182,26 @@ static ssize_t rfkill_fop_read(struct file *file, char 
__user *buf,
return ret;
 }
 
+static int rfkill_airplane_mode_release(struct rfkill_data *data)
+{
+   bool state = rfkill_global_states[RFKILL_TYPE_ALL].cur;
+
+   if (rfkill_apm_owned && data->is_apm_owner) {
+   rfkill_apm_owned = false;
+   data->is_apm_owner = false;
+   rfkill_apm_led_trigger_event(state);
+   return 0;
+   }
+   return -EACCES;
+}
+
 static ssize_t rfkill_fop_write(struct file *file, const char __user *buf,
size_t count, loff_t *pos)
 {
+   struct rfkill_data *data = file->private_data;
struct rfkill *rfkill;
struct rfkill_event ev;
+   int ret = 0;
 
/* we don't need the 'hard' variable but accept it */
if (count < RFKILL_EVENT_SIZE_V1 - 1)
@@ -1199,7 +1216,7 @@ static ssize_t rfkill_fop_write(struct file *file, const 
char __user *buf,
if (copy_from_user(, buf, count))
return -EFAULT;
 
-   if (ev.op != RFKILL_OP_CHANGE && ev.op != RFKILL_OP_CHANGE_ALL)
+   if (ev.op < RFKILL_OP_CHANGE)
return -EINVAL;
 
if (ev.type >= NUM_RFKILL_TYPES)
@@ -1207,6 +1224,25 @@ static ssize_t rfkill_fop_write(struct file *file, const 
char __user *buf,
 

Re: [PATCH 8/9] rfkill: Userspace control for airplane mode

[João Paulo Rechi Vita]

On 8 February 2016 at 17:53, Julian Calaby  wrote:

>> +   if (ev.op == RFKILL_OP_AIRPLANE_MODE_RELEASE) {
>> +   if (rfkill_apm_owned && !data->is_apm_owner) {
>
> Are you sure this is correct?
>
> In the case that airplane mode isn't owned, the
> rfkill_apm_led_trigger_event() call will be a noop, so we should
> arguably not be calling it.
>

Ok, I'm changing the check to be consistent with _CHANGE, so the call
only succeeds if (rfkill_apm_owned && data->is_apm_owner), and return
an error otherwise.

> Also, should we just fail silently if we're not the owner? I.e. what
> does userspace learn from this op failing and is that useful?
>

I think it is better to return an error every time userspace is trying
to call an operation that it was not supposed to call at a certain
state (without acquiring control of the airplane-mode indicator). If a
program has a logic error that makes it call _RELEASE without calling
_ACQUIRE first, it's easier for the programmer to spot the problem if
we return an error here.

>> +   count = -EACCES;
>> +   } else {
>> +   bool state = 
>> rfkill_global_states[RFKILL_TYPE_ALL].cur;
>> +
>> +   rfkill_apm_owned = false;
>> +   data->is_apm_owner = false;
>> +   rfkill_apm_led_trigger_event(state);
>> +   }
>> +   }
>> +
>> +   if (ev.op == RFKILL_OP_AIRPLANE_MODE_CHANGE) {
>> +   if (rfkill_apm_owned && data->is_apm_owner)
>> +   rfkill_apm_led_trigger_event(ev.soft);
>> +   else
>> +   count = -EACCES;
>> +   }
>> +
>> if (ev.op == RFKILL_OP_CHANGE_ALL)
>> rfkill_update_global_state(ev.type, ev.soft);
>>
>> @@ -1230,7 +1261,17 @@ static int rfkill_fop_release(struct inode *inode, 
>> struct file *file)
>> struct rfkill_int_event *ev, *tmp;
>>
>> mutex_lock(_global_mutex);
>> +
>> +   if (data->is_apm_owner) {
>> +   bool state = rfkill_global_states[RFKILL_TYPE_ALL].cur;
>> +
>> +   rfkill_apm_owned = false;
>> +   data->is_apm_owner = false;
>> +   rfkill_apm_led_trigger_event(state);
>
> Also, this code is duplicated from the _RELEASE op above. Would it
> make sense to factor it out into a separate function?
>

Yes, makes sense. This also made me notice I was assigning a negative
value to a size_t variable (count).

>> +   }
>> +
>> list_del(>list);
>> +
>
> (extra line)
>

After factoring out the _RELEASE code it looks better without this
additional line.

>> mutex_unlock(_global_mutex);
>>
>> mutex_destroy(>mtx);
>
> Thanks,
>

Thanks for the review, Julian. I'm sending an updated version.

--
João Paulo Rechi Vita
http://about.me/jprvita

Re: [PATCH 8/9] rfkill: Userspace control for airplane mode

[Julian Calaby]

Hi All,

On Wed, Feb 10, 2016 at 8:36 AM, João Paulo Rechi Vita
 wrote:
> Provide an interface for the airplane-mode indicator be controlled from
> userspace. User has to first acquire the control through
> RFKILL_OP_AIRPLANE_MODE_ACQUIRE and keep the fd open for the whole time
> it wants to be in control of the indicator. Closing the fd or using
> RFKILL_OP_AIRPLANE_MODE_RELEASE restores the default policy.
>
> To change state of the indicator, the RFKILL_OP_AIRPLANE_MODE_CHANGE
> operation is used, passing the value on "struct rfkill_event.soft". If
> the caller has not acquired the airplane-mode control beforehand, the
> operation fails.
>
> Signed-off-by: João Paulo Rechi Vita 

This looks sane to me.

Reviewed-by: Julian Calaby 

Thanks,

-- 
Julian Calaby

Email: julian.cal...@gmail.com
Profile: http://www.google.com/profiles/julian.calaby/

Re: [PATCH 8/9] rfkill: Userspace control for airplane mode

[Dan Williams]

On Mon, 2016-02-08 at 10:41 -0500, João Paulo Rechi Vita wrote:
> Provide an interface for the airplane-mode indicator be controlled
> from
> userspace. User has to first acquire the control through
> RFKILL_OP_AIRPLANE_MODE_ACQUIRE and keep the fd open for the whole
> time
> it wants to be in control of the indicator. Closing the fd or using
> RFKILL_OP_AIRPLANE_MODE_RELEASE restores the default policy.
> 
> To change state of the indicator, the RFKILL_OP_AIRPLANE_MODE_CHANGE
> operation is used, passing the value on "struct rfkill_event.soft".
> If
> the caller has not acquired the airplane-mode control beforehand, the
> operation fails.

I'd like to clarify a bit, so tell me if I'm correct or not.  Using
RFKILL_OP_AIRPLANE_MODE_CHANGE does not actually change any device
state. It's just an indicator with no relationship to any of the
registered rfkill switches, right?

I wonder if setting RFKILL_OP_AIRPLANE_MODE_CHANGE(true) shouldn't also
softblock all switches, otherwise you can set airplane mode all day
long with RFKILL_OP_AIRPLANE_MODE_CHANGE and it doesn't actually enable
airplane mode at all?

Dan

> Signed-off-by: João Paulo Rechi Vita 
> ---
>  Documentation/rfkill.txt| 10 ++
>  include/uapi/linux/rfkill.h |  3 +++
>  net/rfkill/core.c   | 47
> ++---
>  3 files changed, 57 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/rfkill.txt b/Documentation/rfkill.txt
> index b13025a..aa6e014 100644
> --- a/Documentation/rfkill.txt
> +++ b/Documentation/rfkill.txt
> @@ -87,6 +87,7 @@ RFKill provides per-switch LED triggers, which can
> be used to drive LEDs
>  according to the switch state (LED_FULL when blocked, LED_OFF
> otherwise).
>  An airplane-mode indicator LED trigger is also available, which
> triggers
>  LED_FULL when all radios known by RFKill are blocked, and LED_OFF
> otherwise.
> +The airplane-mode indicator LED trigger policy can be overridden by
> userspace.
>  
>  
>  5. Userspace support
> @@ -123,5 +124,14 @@ RFKILL_TYPE
>  The contents of these variables corresponds to the "name", "state"
> and
>  "type" sysfs files explained above.
>  
> +Userspace can also override the default airplane-mode indicator
> policy through
> +/dev/rfkill. Control of the airplane mode indicator has to be
> acquired first,
> +using RFKILL_OP_AIRPLANE_MODE_ACQUIRE, and is only available for one
> userspace
> +application at a time. Closing the fd or using
> RFKILL_OP_AIRPLANE_MODE_RELEASE
> +reverts the airplane-mode indicator back to the default kernel
> policy and makes
> +it available for other applications to take control. Changes to the
> +airplane-mode indicator state can be made using
> RFKILL_OP_AIRPLANE_MODE_CHANGE,
> +passing the new value in the 'soft' field of 'struct rfkill_event'.
> +
>  
>  For further details consult Documentation/ABI/stable/sysfs-class
> -rfkill.
> diff --git a/include/uapi/linux/rfkill.h
> b/include/uapi/linux/rfkill.h
> index 2e00dce..9cb999b 100644
> --- a/include/uapi/linux/rfkill.h
> +++ b/include/uapi/linux/rfkill.h
> @@ -67,6 +67,9 @@ enum rfkill_operation {
>   RFKILL_OP_DEL,
>   RFKILL_OP_CHANGE,
>   RFKILL_OP_CHANGE_ALL,
> + RFKILL_OP_AIRPLANE_MODE_ACQUIRE,
> + RFKILL_OP_AIRPLANE_MODE_RELEASE,
> + RFKILL_OP_AIRPLANE_MODE_CHANGE,
>  };
>  
>  /**
> diff --git a/net/rfkill/core.c b/net/rfkill/core.c
> index fb11547..8067701 100644
> --- a/net/rfkill/core.c
> +++ b/net/rfkill/core.c
> @@ -89,6 +89,7 @@ struct rfkill_data {
>   struct mutexmtx;
>   wait_queue_head_t   read_wait;
>   boolinput_handler;
> + boolis_apm_owner;
>  };
>  
>  
> @@ -123,7 +124,7 @@ static struct {
>  } rfkill_global_states[NUM_RFKILL_TYPES];
>  
>  static bool rfkill_epo_lock_active;
> -
> +static bool rfkill_apm_owned;
>  
>  #ifdef CONFIG_RFKILL_LEDS
>  static struct led_trigger rfkill_apm_led_trigger;
> @@ -350,7 +351,8 @@ static void rfkill_update_global_state(enum
> rfkill_type type, bool blocked)
>  
>   for (i = 0; i < NUM_RFKILL_TYPES; i++)
>   rfkill_global_states[i].cur = blocked;
> - rfkill_apm_led_trigger_event(blocked);
> + if (!rfkill_apm_owned)
> + rfkill_apm_led_trigger_event(blocked);
>  }
>  
>  #ifdef CONFIG_RFKILL_INPUT
> @@ -1183,6 +1185,7 @@ static ssize_t rfkill_fop_read(struct file
> *file, char __user *buf,
>  static ssize_t rfkill_fop_write(struct file *file, const char __user
> *buf,
>   size_t count, loff_t *pos)
>  {
> + struct rfkill_data *data = file->private_data;
>   struct rfkill *rfkill;
>   struct rfkill_event ev;
>  
> @@ -1199,7 +1202,7 @@ static ssize_t rfkill_fop_write(struct file
> *file, const char __user *buf,
>   if (copy_from_user(, buf, count))
>   return -EFAULT;
>  
> - if (ev.op != RFKILL_OP_CHANGE && ev.op !=
> RFKILL_OP_CHANGE_ALL)
> + if (ev.op < 

Re: [PATCH 8/9] rfkill: Userspace control for airplane mode

[Marcel Holtmann]

Hi Joa Paulo,

> Provide an interface for the airplane-mode indicator be controlled from
> userspace. User has to first acquire the control through
> RFKILL_OP_AIRPLANE_MODE_ACQUIRE and keep the fd open for the whole time
> it wants to be in control of the indicator. Closing the fd or using
> RFKILL_OP_AIRPLANE_MODE_RELEASE restores the default policy.
> 
> To change state of the indicator, the RFKILL_OP_AIRPLANE_MODE_CHANGE
> operation is used, passing the value on "struct rfkill_event.soft". If
> the caller has not acquired the airplane-mode control beforehand, the
> operation fails.

as explained in an earlier response, the concept Airplane Mode seems to be 
imposing policy into the kernel. Do we really want have this as a kernel 
exposed API.

Regards

Marcel

[PATCH 8/9] rfkill: Userspace control for airplane mode

[João Paulo Rechi Vita]

Provide an interface for the airplane-mode indicator be controlled from
userspace. User has to first acquire the control through
RFKILL_OP_AIRPLANE_MODE_ACQUIRE and keep the fd open for the whole time
it wants to be in control of the indicator. Closing the fd or using
RFKILL_OP_AIRPLANE_MODE_RELEASE restores the default policy.

To change state of the indicator, the RFKILL_OP_AIRPLANE_MODE_CHANGE
operation is used, passing the value on "struct rfkill_event.soft". If
the caller has not acquired the airplane-mode control beforehand, the
operation fails.

Signed-off-by: João Paulo Rechi Vita 
---
 Documentation/rfkill.txt| 10 ++
 include/uapi/linux/rfkill.h |  3 +++
 net/rfkill/core.c   | 47 ++---
 3 files changed, 57 insertions(+), 3 deletions(-)

diff --git a/Documentation/rfkill.txt b/Documentation/rfkill.txt
index b13025a..aa6e014 100644
--- a/Documentation/rfkill.txt
+++ b/Documentation/rfkill.txt
@@ -87,6 +87,7 @@ RFKill provides per-switch LED triggers, which can be used to 
drive LEDs
 according to the switch state (LED_FULL when blocked, LED_OFF otherwise).
 An airplane-mode indicator LED trigger is also available, which triggers
 LED_FULL when all radios known by RFKill are blocked, and LED_OFF otherwise.
+The airplane-mode indicator LED trigger policy can be overridden by userspace.
 
 
 5. Userspace support
@@ -123,5 +124,14 @@ RFKILL_TYPE
 The contents of these variables corresponds to the "name", "state" and
 "type" sysfs files explained above.
 
+Userspace can also override the default airplane-mode indicator policy through
+/dev/rfkill. Control of the airplane mode indicator has to be acquired first,
+using RFKILL_OP_AIRPLANE_MODE_ACQUIRE, and is only available for one userspace
+application at a time. Closing the fd or using RFKILL_OP_AIRPLANE_MODE_RELEASE
+reverts the airplane-mode indicator back to the default kernel policy and makes
+it available for other applications to take control. Changes to the
+airplane-mode indicator state can be made using RFKILL_OP_AIRPLANE_MODE_CHANGE,
+passing the new value in the 'soft' field of 'struct rfkill_event'.
+
 
 For further details consult Documentation/ABI/stable/sysfs-class-rfkill.
diff --git a/include/uapi/linux/rfkill.h b/include/uapi/linux/rfkill.h
index 2e00dce..9cb999b 100644
--- a/include/uapi/linux/rfkill.h
+++ b/include/uapi/linux/rfkill.h
@@ -67,6 +67,9 @@ enum rfkill_operation {
RFKILL_OP_DEL,
RFKILL_OP_CHANGE,
RFKILL_OP_CHANGE_ALL,
+   RFKILL_OP_AIRPLANE_MODE_ACQUIRE,
+   RFKILL_OP_AIRPLANE_MODE_RELEASE,
+   RFKILL_OP_AIRPLANE_MODE_CHANGE,
 };
 
 /**
diff --git a/net/rfkill/core.c b/net/rfkill/core.c
index fb11547..8067701 100644
--- a/net/rfkill/core.c
+++ b/net/rfkill/core.c
@@ -89,6 +89,7 @@ struct rfkill_data {
struct mutexmtx;
wait_queue_head_t   read_wait;
boolinput_handler;
+   boolis_apm_owner;
 };
 
 
@@ -123,7 +124,7 @@ static struct {
 } rfkill_global_states[NUM_RFKILL_TYPES];
 
 static bool rfkill_epo_lock_active;
-
+static bool rfkill_apm_owned;
 
 #ifdef CONFIG_RFKILL_LEDS
 static struct led_trigger rfkill_apm_led_trigger;
@@ -350,7 +351,8 @@ static void rfkill_update_global_state(enum rfkill_type 
type, bool blocked)
 
for (i = 0; i < NUM_RFKILL_TYPES; i++)
rfkill_global_states[i].cur = blocked;
-   rfkill_apm_led_trigger_event(blocked);
+   if (!rfkill_apm_owned)
+   rfkill_apm_led_trigger_event(blocked);
 }
 
 #ifdef CONFIG_RFKILL_INPUT
@@ -1183,6 +1185,7 @@ static ssize_t rfkill_fop_read(struct file *file, char 
__user *buf,
 static ssize_t rfkill_fop_write(struct file *file, const char __user *buf,
size_t count, loff_t *pos)
 {
+   struct rfkill_data *data = file->private_data;
struct rfkill *rfkill;
struct rfkill_event ev;
 
@@ -1199,7 +1202,7 @@ static ssize_t rfkill_fop_write(struct file *file, const 
char __user *buf,
if (copy_from_user(, buf, count))
return -EFAULT;
 
-   if (ev.op != RFKILL_OP_CHANGE && ev.op != RFKILL_OP_CHANGE_ALL)
+   if (ev.op < RFKILL_OP_CHANGE)
return -EINVAL;
 
if (ev.type >= NUM_RFKILL_TYPES)
@@ -1207,6 +1210,34 @@ static ssize_t rfkill_fop_write(struct file *file, const 
char __user *buf,
 
mutex_lock(_global_mutex);
 
+   if (ev.op == RFKILL_OP_AIRPLANE_MODE_ACQUIRE) {
+   if (rfkill_apm_owned && !data->is_apm_owner) {
+   count = -EACCES;
+   } else {
+   rfkill_apm_owned = true;
+   data->is_apm_owner = true;
+   }
+   }
+
+   if (ev.op == RFKILL_OP_AIRPLANE_MODE_RELEASE) {
+   if (rfkill_apm_owned && !data->is_apm_owner) {
+   count = -EACCES;
+   } else {
+ 

Re: [PATCH 8/9] rfkill: Userspace control for airplane mode

[Johannes Berg]

On 2016-02-08 17:20, Marcel Holtmann wrote:


as explained in an earlier response, the concept Airplane Mode seems
to be imposing policy into the kernel. Do we really want have this as
a kernel exposed API.


This patch is the one that *solves* that problem ... please read it more 
carefully?


johannes

Re: [PATCH 8/9] rfkill: Userspace control for airplane mode

[João Paulo Rechi Vita]

Hello Marcel,

On 8 February 2016 at 11:20, Marcel Holtmann  wrote:
> Hi Joa Paulo,
>
>> Provide an interface for the airplane-mode indicator be controlled from
>> userspace. User has to first acquire the control through
>> RFKILL_OP_AIRPLANE_MODE_ACQUIRE and keep the fd open for the whole time
>> it wants to be in control of the indicator. Closing the fd or using
>> RFKILL_OP_AIRPLANE_MODE_RELEASE restores the default policy.
>>
>> To change state of the indicator, the RFKILL_OP_AIRPLANE_MODE_CHANGE
>> operation is used, passing the value on "struct rfkill_event.soft". If
>> the caller has not acquired the airplane-mode control beforehand, the
>> operation fails.
>
> as explained in an earlier response, the concept Airplane Mode seems to be 
> imposing policy into the kernel. Do we really want have this as a kernel 
> exposed API.
>

On that very same thread we decided to keep using the "airplane mode"
name both for when having the default policy of "set it when all
radios are off" or when allowing userspace to override the default.
Please see the following message from Johannes
http://www.spinics.net/lists/linux-wireless/msg146069.html and let me
know if that covers your concern.

Thanks!

--
João Paulo Rechi Vita
http://about.me/jprvita

Re: [PATCH 8/9] rfkill: Userspace control for airplane mode

[João Paulo Rechi Vita]

On 8 February 2016 at 11:11, Dan Williams  wrote:
> On Mon, 2016-02-08 at 10:41 -0500, João Paulo Rechi Vita wrote:
>> Provide an interface for the airplane-mode indicator be controlled
>> from
>> userspace. User has to first acquire the control through
>> RFKILL_OP_AIRPLANE_MODE_ACQUIRE and keep the fd open for the whole
>> time
>> it wants to be in control of the indicator. Closing the fd or using
>> RFKILL_OP_AIRPLANE_MODE_RELEASE restores the default policy.
>>
>> To change state of the indicator, the RFKILL_OP_AIRPLANE_MODE_CHANGE
>> operation is used, passing the value on "struct rfkill_event.soft".
>> If
>> the caller has not acquired the airplane-mode control beforehand, the
>> operation fails.
>
> I'd like to clarify a bit, so tell me if I'm correct or not.  Using
> RFKILL_OP_AIRPLANE_MODE_CHANGE does not actually change any device
> state. It's just an indicator with no relationship to any of the
> registered rfkill switches, right?
>

Yes, that's correct, and it is the intended behavior.

> I wonder if setting RFKILL_OP_AIRPLANE_MODE_CHANGE(true) shouldn't also
> softblock all switches, otherwise you can set airplane mode all day
> long with RFKILL_OP_AIRPLANE_MODE_CHANGE and it doesn't actually enable
> airplane mode at all?
>

The idea behind it is to just provide the mechanism for userspace to
decide what exactly being in airplane mode means, so it would
set/unset the indicator in the right moment.

--
João Paulo Rechi Vita
http://about.me/jprvita

Re: [PATCH 8/9] rfkill: Userspace control for airplane mode

[Julian Calaby]

Hi João,

On Tue, Feb 9, 2016 at 2:41 AM, João Paulo Rechi Vita  wrote:
> Provide an interface for the airplane-mode indicator be controlled from
> userspace. User has to first acquire the control through
> RFKILL_OP_AIRPLANE_MODE_ACQUIRE and keep the fd open for the whole time
> it wants to be in control of the indicator. Closing the fd or using
> RFKILL_OP_AIRPLANE_MODE_RELEASE restores the default policy.
>
> To change state of the indicator, the RFKILL_OP_AIRPLANE_MODE_CHANGE
> operation is used, passing the value on "struct rfkill_event.soft". If
> the caller has not acquired the airplane-mode control beforehand, the
> operation fails.
>
> Signed-off-by: João Paulo Rechi Vita 
> ---
>  Documentation/rfkill.txt| 10 ++
>  include/uapi/linux/rfkill.h |  3 +++
>  net/rfkill/core.c   | 47 
> ++---
>  3 files changed, 57 insertions(+), 3 deletions(-)
>
> diff --git a/net/rfkill/core.c b/net/rfkill/core.c
> index fb11547..8067701 100644
> --- a/net/rfkill/core.c
> +++ b/net/rfkill/core.c
> @@ -1207,6 +1210,34 @@ static ssize_t rfkill_fop_write(struct file *file, 
> const char __user *buf,
>
> mutex_lock(_global_mutex);
>
> +   if (ev.op == RFKILL_OP_AIRPLANE_MODE_ACQUIRE) {
> +   if (rfkill_apm_owned && !data->is_apm_owner) {
> +   count = -EACCES;
> +   } else {
> +   rfkill_apm_owned = true;
> +   data->is_apm_owner = true;
> +   }
> +   }
> +
> +   if (ev.op == RFKILL_OP_AIRPLANE_MODE_RELEASE) {
> +   if (rfkill_apm_owned && !data->is_apm_owner) {

Are you sure this is correct?

In the case that airplane mode isn't owned, the
rfkill_apm_led_trigger_event() call will be a noop, so we should
arguably not be calling it.

Also, should we just fail silently if we're not the owner? I.e. what
does userspace learn from this op failing and is that useful?

> +   count = -EACCES;
> +   } else {
> +   bool state = 
> rfkill_global_states[RFKILL_TYPE_ALL].cur;
> +
> +   rfkill_apm_owned = false;
> +   data->is_apm_owner = false;
> +   rfkill_apm_led_trigger_event(state);
> +   }
> +   }
> +
> +   if (ev.op == RFKILL_OP_AIRPLANE_MODE_CHANGE) {
> +   if (rfkill_apm_owned && data->is_apm_owner)
> +   rfkill_apm_led_trigger_event(ev.soft);
> +   else
> +   count = -EACCES;
> +   }
> +
> if (ev.op == RFKILL_OP_CHANGE_ALL)
> rfkill_update_global_state(ev.type, ev.soft);
>
> @@ -1230,7 +1261,17 @@ static int rfkill_fop_release(struct inode *inode, 
> struct file *file)
> struct rfkill_int_event *ev, *tmp;
>
> mutex_lock(_global_mutex);
> +
> +   if (data->is_apm_owner) {
> +   bool state = rfkill_global_states[RFKILL_TYPE_ALL].cur;
> +
> +   rfkill_apm_owned = false;
> +   data->is_apm_owner = false;
> +   rfkill_apm_led_trigger_event(state);

Also, this code is duplicated from the _RELEASE op above. Would it
make sense to factor it out into a separate function?

> +   }
> +
> list_del(>list);
> +

(extra line)

> mutex_unlock(_global_mutex);
>
> mutex_destroy(>mtx);

Thanks,

-- 
Julian Calaby

Email: julian.cal...@gmail.com
Profile: http://www.google.com/profiles/julian.calaby/