[RFC 1/2] nl80211: add common API to configure SAR power limitations.

[Brian Norris]

Hi Carl,

Sorry, I lied; I have a few more notes after spending another day
looking at this:

On Tue, Sep 22, 2020 at 01:49:34PM +0800, Carl Huang wrote:
> --- a/include/net/cfg80211.h
> +++ b/include/net/cfg80211.h
> @@ -1663,6 +1663,55 @@ struct station_info {
> +/**
> + * @struct cfg80211_sar_chan_ranges - sar frequency ranges
> + * @index: the index of this range. It's used to specify
> + *	the frequency range when setting SAR power limitation
> + * @start_freq:  start channel frequency in kHZ. For example,
> + *	2.4G channel 1 is represented as 2412000
> + * @end_freq:    end channel frequency in kHZ

If you accept my comments in nl80211.h, you'll want to change this too.

> + */
> +struct cfg80211_sar_freq_ranges {
> +	u8 index;
> +	u32 start_freq;
> +	u32 end_freq;
> +};

> --- a/include/uapi/linux/nl80211.h
> +++ b/include/uapi/linux/nl80211.h

> + * @NL80211_SAR_ATTR_SPECS_START_FREQ: Required (u32) value to specify the start
> + *	frequency of this range to register SAR capability to wihpy and the unit
> + *	is kHZ
> + *
> + * @NL80211_SAR_ATTR_SPECS_END_FREQ: Required (u32) value to specify the end frequency
> + *	of this range to register SAR capability to wiphy and the unit is kHZ

The documentation here isn't clear whether these are center frequencies
or band edges. The cfg80211 comments do though (center freq). However,
this is inconsistent with NL80211_ATTR_FREQ_RANGE_START and
NL80211_ATTR_FREQ_RANGE_END -- I'd suggest being consistent?

> --- a/net/mac80211/cfg.c
> +++ b/net/mac80211/cfg.c

> @@ -15331,6 +15496,14 @@ static const struct genl_ops nl80211_ops[] = {
>  		.internal_flags = NL80211_FLAG_NEED_NETDEV |
>  				  NL80211_FLAG_NEED_RTNL,
>  	},
> +	{
> +		.cmd = NL80211_CMD_SET_SAR_SPECS,
> +		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
> +		.doit = nl80211_set_sar_specs,
> +		.flags = GENL_UNS_ADMIN_PERM,
> +		.internal_flags = NL80211_FLAG_NEED_NETDEV_UP |

Is there a reason this needs to be UP? CMD_SET_WIPHY (which can also
configure TX power, a little differently) does not. Seems like this
could just be NL80211_FLAG_NEED_NETDEV -- or maybe not even that, if we
switch this to a WIPHY command like Johannes noted.

Brian

> +				  NL80211_FLAG_NEED_RTNL,
> +	},
>  };