[PATCH] nl80211: Provide per channel maximum regulatory transmit power

[PATCH] nl80211: Provide per channel maximum regulatory transmit power

[Helmut Schaa]

In some cases its not only required to know the maximum transmit power
the hw is capable of. Instead, userspace (hostapd) might want to know
the maximum transmit power as defined in the current regulatory domain
(for example for 802.11d country IEs).

Hence, provide that information to user space via nl80211.

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
---
 include/uapi/linux/nl80211.h |    3 +++
 net/wireless/nl80211.c       |    4 ++++
 2 files changed, 7 insertions(+)

diff --git a/include/uapi/linux/nl80211.h b/include/uapi/linux/nl80211.h
index fde2c02..6130278 100644
--- a/include/uapi/linux/nl80211.h
+++ b/include/uapi/linux/nl80211.h
@@ -2230,6 +2230,8 @@ enum nl80211_band_attr {
  *	isn't possible
  * @NL80211_FREQUENCY_ATTR_MAX: highest frequency attribute number
  *	currently defined
+ * @NL80211_FREQUENCY_ATTR_MAX_REG_TX_POWER: Maximum regulatory transmission
+ *	power in mBm (100 * dBm).
  * @__NL80211_FREQUENCY_ATTR_AFTER_LAST: internal use
  */
 enum nl80211_frequency_attr {
@@ -2246,6 +2248,7 @@ enum nl80211_frequency_attr {
 	NL80211_FREQUENCY_ATTR_NO_HT40_PLUS,
 	NL80211_FREQUENCY_ATTR_NO_80MHZ,
 	NL80211_FREQUENCY_ATTR_NO_160MHZ,
+	NL80211_FREQUENCY_ATTR_MAX_REG_TX_POWER,
 
 	/* keep last */
 	__NL80211_FREQUENCY_ATTR_AFTER_LAST,
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 626dc3b..7c22355 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -584,6 +584,10 @@ static int nl80211_msg_put_channel(struct sk_buff *msg,
 			DBM_TO_MBM(chan->max_power)))
 		goto nla_put_failure;
 
+	if (nla_put_u32(msg, NL80211_FREQUENCY_ATTR_MAX_REG_TX_POWER,
+			DBM_TO_MBM(chan->max_reg_power)))
+		goto nla_put_failure;
+
 	return 0;
 
  nla_put_failure:
-- 
1.7.10.4

Re: [PATCH] nl80211: Provide per channel maximum regulatory transmit power

[Johannes Berg]

On Wed, 2013-10-02 at 09:43 +0200, Helmut Schaa wrote:
> In some cases its not only required to know the maximum transmit power
> the hw is capable of. Instead, userspace (hostapd) might want to know
> the maximum transmit power as defined in the current regulatory domain
> (for example for 802.11d country IEs).

Why wouldn't it use (the equivalent of) "iw reg get" for that?


> +	if (nla_put_u32(msg, NL80211_FREQUENCY_ATTR_MAX_REG_TX_POWER,
> +			DBM_TO_MBM(chan->max_reg_power)))
> +		goto nla_put_failure;

This would have to go into the "if (large)" part because otherwise older
userspace can't read the info at all since it overflows the buffer.

johannes

Re: [PATCH] nl80211: Provide per channel maximum regulatory transmit power

[Helmut Schaa]

On Wed, Oct 2, 2013 at 10:44 AM, Johannes Berg
<johannes@sipsolutions.net> wrote:
> On Wed, 2013-10-02 at 09:43 +0200, Helmut Schaa wrote:
>> In some cases its not only required to know the maximum transmit power
>> the hw is capable of. Instead, userspace (hostapd) might want to know
>> the maximum transmit power as defined in the current regulatory domain
>> (for example for 802.11d country IEs).
>
> Why wouldn't it use (the equivalent of) "iw reg get" for that?

Might be the more sane approach.

I noticed that hostapd generates 11d IEs based on the channel list it
reads from the kernel.
Thus restricting STAs to the max tx power the hw is capable of. Just
adding the max regulatory
tx power looked like an easy solution :)

Jouni, would you be ok with using the kernels regulatory domain for
11d IEs in hostapd?

Thanks,
Helmut