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    SubjectRe: [PATCH 8/9] rfkill: Userspace control for airplane mode
    Hi João,

    On Tue, Feb 9, 2016 at 2:41 AM, João Paulo Rechi Vita <jprvita@gmail.com> 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 <jprvita@endlessm.com>
    > ---
    > 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(&rfkill_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(&rfkill_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(&data->list);
    > +

    (extra line)

    > mutex_unlock(&rfkill_global_mutex);
    >
    > mutex_destroy(&data->mtx);

    Thanks,

    --
    Julian Calaby

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

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