Date:	Thu, 12 May 2016 17:34:37 +0800
From:	Wei-Ning Huang <wnhuang@...gle.com>
To:	Dan Williams <dcbw@...hat.com>
Cc:	Linux-Wireless <linux-wireless@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Johannes Berg <johannes@...solutions.net>,
	Sameer Nanda <snanda@...omium.org>,
	Todd Broch <tbroch@...omium.org>, davem@...emloft.net,
	netdev@...r.kernel.org
Subject: Re: [PATCH] cfg80211/nl80211: add wifi tx power mode switching support

On Thu, May 12, 2016 at 2:33 AM, Dan Williams <dcbw@...hat.com> wrote:
> On Wed, 2016-05-11 at 13:03 +0800, Wei-Ning Huang wrote:
>> On Fri, May 6, 2016 at 4:19 PM, Wei-Ning Huang <wnhuang@...gle.com>
>> wrote:
>> >
>> > On Fri, May 6, 2016 at 12:07 AM, Dan Williams <dcbw@...hat.com>
>> > wrote:
>> > >
>> > >
>> > > On Thu, 2016-05-05 at 14:44 +0800, Wei-Ning Huang wrote:
>> > > >
>> > > > Recent new hardware has the ability to switch between tablet
>> > > > mode and
>> > > > clamshell mode. To optimize WiFi performance, we want to be
>> > > > able to
>> > > > use
>> > > > different power table between modes. This patch adds a new
>> > > > netlink
>> > > > message type and cfg80211_ops function to allow userspace to
>> > > > trigger
>> > > > a
>> > > > power mode switch for a given wireless interface.
>> > > >
>> > > > Signed-off-by: Wei-Ning Huang <wnhuang@...omium.org>
>> > > > ---
>> > > >  include/net/cfg80211.h       | 11 +++++++++++
>> > > >  include/uapi/linux/nl80211.h | 21 +++++++++++++++++++++
>> > > >  net/wireless/nl80211.c       | 16 ++++++++++++++++
>> > > >  net/wireless/rdev-ops.h      | 22 ++++++++++++++++++++++
>> > > >  net/wireless/trace.h         | 20 ++++++++++++++++++++
>> > > >  5 files changed, 90 insertions(+)
>> > > >
>> > > > diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
>> > > > index 9e1b24c..aa77fa0 100644
>> > > > --- a/include/net/cfg80211.h
>> > > > +++ b/include/net/cfg80211.h
>> > > > @@ -2370,6 +2370,12 @@ struct cfg80211_qos_map {
>> > > >   * @get_tx_power: store the current TX power into the dbm
>> > > > variable;
>> > > >   *   return 0 if successful
>> > > >   *
>> > > > + * @set_tx_power_mode: set the transmit power mode. Some
>> > > > device have
>> > > > the ability
>> > > > + *   to transform between different mode such as clamshell and
>> > > > tablet mode.
>> > > > + *   set_tx_power_mode allows setting of different TX power
>> > > > mode at runtime.
>> > > > + * @get_tx_power_mode: store the current TX power mode into
>> > > > the mode
>> > > > variable;
>> > > > + *   return 0 if successful
>> > > > + *
>> > > >   * @set_wds_peer: set the WDS peer for a WDS interface
>> > > >   *
>> > > >   * @rfkill_poll: polls the hw rfkill line, use cfg80211
>> > > > reporting
>> > > > @@ -2631,6 +2637,11 @@ struct cfg80211_ops {
>> > > >       int     (*get_tx_power)(struct wiphy *wiphy, struct
>> > > > wireless_dev *wdev,
>> > > >                               int *dbm);
>> > > >
>> > > > +     int     (*set_tx_power_mode)(struct wiphy *wiphy,
>> > > > +                                  enum nl80211_tx_power_mode
>> > > > mode);
>> > > > +     int     (*get_tx_power_mode)(struct wiphy *wiphy,
>> > > > +                                  enum nl80211_tx_power_mode
>> > > > *mode);
>> > > > +
>> > > >       int     (*set_wds_peer)(struct wiphy *wiphy, struct
>> > > > net_device *dev,
>> > > >                               const u8 *addr);
>> > > >
>> > > > diff --git a/include/uapi/linux/nl80211.h
>> > > > b/include/uapi/linux/nl80211.h
>> > > > index 5a30a75..9b1888a 100644
>> > > > --- a/include/uapi/linux/nl80211.h
>> > > > +++ b/include/uapi/linux/nl80211.h
>> > > > @@ -1796,6 +1796,9 @@ enum nl80211_commands {
>> > > >   *   connecting to a PCP, and in %NL80211_CMD_START_AP to
>> > > > start
>> > > >   *   a PCP instead of AP. Relevant for DMG networks only.
>> > > >   *
>> > > > + * @NL80211_ATTR_WIPHY_TX_POWER_MODE: Transmit power mode. See
>> > > > + *      &enum nl80211_tx_power_mode for possible values.
>> > > > + *
>> > > >   * @NUM_NL80211_ATTR: total number of nl80211_attrs available
>> > > >   * @NL80211_ATTR_MAX: highest attribute number currently
>> > > > defined
>> > > >   * @__NL80211_ATTR_AFTER_LAST: internal use
>> > > > @@ -2172,6 +2175,8 @@ enum nl80211_attrs {
>> > > >
>> > > >       NL80211_ATTR_PBSS,
>> > > >
>> > > > +     NL80211_ATTR_WIPHY_TX_POWER_MODE,
>> > > > +
>> > > >       /* add attributes here, update the policy in nl80211.c */
>> > > >
>> > > >       __NL80211_ATTR_AFTER_LAST,
>> > > > @@ -3703,6 +3708,22 @@ enum nl80211_tx_power_setting {
>> > > >  };
>> > > >
>> > > >  /**
>> > > > + * enum nl80211_tx_power_mode - TX power mode setting
>> > > > + * @NL80211_TX_POWER_LOW: general low TX power mode
>> > > > + * @NL80211_TX_POWER_MEDIUM: general medium TX power mode
>> > > > + * @NL80211_TX_POWER_HIGH: general high TX power mode
>> > > > + * @NL80211_TX_POWER_CLAMSHELL: clamshell mode TX power mode
>> > > > + * @NL80211_TX_POWER_TABLET: tablet mode TX power mode
>> > > > + */
>> > > > +enum nl80211_tx_power_mode {
>> > > > +     NL80211_TX_POWER_LOW,
>> > > > +     NL80211_TX_POWER_MEDIUM,
>> > > > +     NL80211_TX_POWER_HIGH,
>> > > > +     NL80211_TX_POWER_CLAMSHELL,
>> > > > +     NL80211_TX_POWER_TABLET,
>> > >
>> > > "clamshell" and "tablet" probably mean many different things to
>> > > many
>> > > different people with respect to whether or not they should do
>> > > anything
>> > > with power saving or wifi.  I feel like a more generic interface
>> > > is
>> > > needed here.
>> > We could probably drop those two CLAMSHELL and TABLET constant or
>> > describing what they mean
>> > in more detail?
>> >
>> > >
>> > >
>> > > Could this be already done by:
>> > > @NL80211_ATTR_WIPHY_TX_POWER_SETTING = NL80211_TX_POWER_LIMITED
>> > > @NL80211_ATTR_WIPHY_TX_POWER_LEVEL = <limit for clamshell/tablet
>> > > mode>
>> > >
>> > > and then the device would be able to change its TX power as it
>> > > saw fit
>> > > up to that limit set by your application which figures out
>> > > whether it's
>> > > in clamshell or tablet mode?
>> > We usually want different power settings in different band/channel.
>> > For example, we can have three different power settings
>> > in 2.4Ghz, channels 36-64 & channels 100+ on 5Ghz. In this case, we
>> > can not simply set a fixed number to the power level.
>> > A power table is required to map channel/band to actual power
>> > limit.
>> > For most of the driver, changing power table requires loading
>> > a new set of calibration data from either devicetree or ACPI. Due
>> > to
>> > this, a new message type is required to allow the driver to
>> > switch between tables.
>> >
>> > Wei-Ning
>> Hi Dan,
>>
>> Does this make sense to you? If so I'll send another patch to clarify
>> the term clamshell / tablet mode.
>> Thanks for reviewing.
>
> Yes, you're right that NL80211_ATTR_WIPHY_TX_POWER_SETTING is probably
> too limiting.  But I feel that the constants that you've proposed are
> too "magic" and will mean many different things to different driver
> writers and userspace clients.  I think it would be better implemented
> as a request to simply load specific power calibration data or a new
> power table, instead of attempting to classify power tables through
> kernel constants that could mean something different to everyone.

Dan, Thanks for the pointer. Passing the power table/calibration data
name instead of
constants sounds reasonable.

Johannes, I feel like being able to set calibration data at runtime is
something common
to all wireless drivers, so instead of using vendor commands what do
you think if I pass
the calibration data name instead of using those magic constants? This
way, userspace
does not need to know the details of what band/range power limit the
driver supports. It
allows for flexible driver side implementation and easier for
userspace to control.

Wei-Ning

>
> Dan
>
>> Wei-Ning
>> >
>> > >
>> > >
>> > >
>> > > Dan
>> > >
>> > > >
>> > > > +};
>> > > > +
>> > > > +/**
>> > > >   * enum nl80211_packet_pattern_attr - packet pattern attribute
>> > > >   * @__NL80211_PKTPAT_INVALID: invalid number for nested
>> > > > attribute
>> > > >   * @NL80211_PKTPAT_PATTERN: the pattern, values where the mask
>> > > > has
>> > > > diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
>> > > > index 056a730..61b474d 100644
>> > > > --- a/net/wireless/nl80211.c
>> > > > +++ b/net/wireless/nl80211.c
>> > > > @@ -402,6 +402,7 @@ static const struct nla_policy
>> > > > nl80211_policy[NUM_NL80211_ATTR] = {
>> > > >       [NL80211_ATTR_SCHED_SCAN_DELAY] = { .type = NLA_U32 },
>> > > >       [NL80211_ATTR_REG_INDOOR] = { .type = NLA_FLAG },
>> > > >       [NL80211_ATTR_PBSS] = { .type = NLA_FLAG },
>> > > > +     [NL80211_ATTR_WIPHY_TX_POWER_MODE] = { .type = NLA_U32 },
>> > > >  };
>> > > >
>> > > >  /* policy for the key attributes */
>> > > > @@ -2218,6 +2219,21 @@ static int nl80211_set_wiphy(struct
>> > > > sk_buff
>> > > > *skb, struct genl_info *info)
>> > > >                       return result;
>> > > >       }
>> > > >
>> > > > +     if (info->attrs[NL80211_ATTR_WIPHY_TX_POWER_MODE]) {
>> > > > +             enum nl80211_tx_power_mode mode;
>> > > > +             int idx = 0;
>> > > > +
>> > > > +             if (!rdev->ops->set_tx_power_mode)
>> > > > +                     return -EOPNOTSUPP;
>> > > > +
>> > > > +             idx = NL80211_ATTR_WIPHY_TX_POWER_MODE;
>> > > > +             mode = nla_get_u32(info->attrs[idx]);
>> > > > +
>> > > > +             result = rdev_set_tx_power_mode(rdev, mode);
>> > > > +             if (result)
>> > > > +                     return result;
>> > > > +     }
>> > > > +
>> > > >       if (info->attrs[NL80211_ATTR_WIPHY_ANTENNA_TX] &&
>> > > >           info->attrs[NL80211_ATTR_WIPHY_ANTENNA_RX]) {
>> > > >               u32 tx_ant, rx_ant;
>> > > > diff --git a/net/wireless/rdev-ops.h b/net/wireless/rdev-ops.h
>> > > > index 8ae0c04..c3a1035 100644
>> > > > --- a/net/wireless/rdev-ops.h
>> > > > +++ b/net/wireless/rdev-ops.h
>> > > > @@ -552,6 +552,28 @@ static inline int rdev_get_tx_power(struct
>> > > > cfg80211_registered_device *rdev,
>> > > >       return ret;
>> > > >  }
>> > > >
>> > > > +static inline int
>> > > > +rdev_set_tx_power_mode(struct cfg80211_registered_device
>> > > > *rdev,
>> > > > +                    enum nl80211_tx_power_mode mode)
>> > > > +{
>> > > > +     int ret;
>> > > > +     trace_rdev_set_tx_power_mode(&rdev->wiphy, mode);
>> > > > +     ret = rdev->ops->set_tx_power_mode(&rdev->wiphy, mode);
>> > > > +     trace_rdev_return_int(&rdev->wiphy, ret);
>> > > > +     return ret;
>> > > > +}
>> > > > +
>> > > > +static inline int
>> > > > +rdev_get_tx_power_mode(struct cfg80211_registered_device
>> > > > *rdev,
>> > > > +                    enum nl80211_tx_power_mode *mode)
>> > > > +{
>> > > > +     int ret;
>> > > > +     trace_rdev_get_tx_power_mode(&rdev->wiphy);
>> > > > +     ret = rdev->ops->get_tx_power_mode(&rdev->wiphy, mode);
>> > > > +     trace_rdev_return_int_int(&rdev->wiphy, ret, *mode);
>> > > > +     return ret;
>> > > > +}
>> > > > +
>> > > >  static inline int rdev_set_wds_peer(struct
>> > > > cfg80211_registered_device *rdev,
>> > > >                                   struct net_device *dev, const
>> > > > u8
>> > > > *addr)
>> > > >  {
>> > > > diff --git a/net/wireless/trace.h b/net/wireless/trace.h
>> > > > index 09b242b..132c8c2 100644
>> > > > --- a/net/wireless/trace.h
>> > > > +++ b/net/wireless/trace.h
>> > > > @@ -1420,6 +1420,26 @@ TRACE_EVENT(rdev_set_tx_power,
>> > > >                 WIPHY_PR_ARG, WDEV_PR_ARG,__entry->type,
>> > > > __entry-
>> > > > >
>> > > > > mbm)
>> > > >  );
>> > > >
>> > > > +DEFINE_EVENT(wiphy_only_evt, rdev_get_tx_power_mode,
>> > > > +     TP_PROTO(struct wiphy *wiphy),
>> > > > +     TP_ARGS(wiphy)
>> > > > +);
>> > > > +
>> > > > +TRACE_EVENT(rdev_set_tx_power_mode,
>> > > > +     TP_PROTO(struct wiphy *wiphy, enum nl80211_tx_power_mode
>> > > > mode),
>> > > > +     TP_ARGS(wiphy, mode),
>> > > > +     TP_STRUCT__entry(
>> > > > +             WIPHY_ENTRY
>> > > > +             __field(enum nl80211_tx_power_mode, mode)
>> > > > +     ),
>> > > > +     TP_fast_assign(
>> > > > +             WIPHY_ASSIGN;
>> > > > +             __entry->mode = mode;
>> > > > +     ),
>> > > > +     TP_printk(WIPHY_PR_FMT ", mode: %d",
>> > > > +               WIPHY_PR_ARG, __entry->mode)
>> > > > +);
>> > > > +
>> > > >  TRACE_EVENT(rdev_return_int_int,
>> > > >       TP_PROTO(struct wiphy *wiphy, int func_ret, int
>> > > > func_fill),
>> > > >       TP_ARGS(wiphy, func_ret, func_fill),
>> >
>> >
>> >
>> > --
>> > Wei-Ning Huang, 黃偉寧 | Software Engineer, Google Inc., Taiwan |
>> > wnhuang@...gle.com | Cell: +886 910-380678
>>
>>



-- 
Wei-Ning Huang, 黃偉寧 | Software Engineer, Google Inc., Taiwan |
wnhuang@...gle.com | Cell: +886 910-380678

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