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From: Johannes Berg <johannes@sipsolutions.net>
To: Kalle Valo <kvalo@codeaurora.org>,
	Brian Norris <briannorris@chromium.org>
Cc: Jouni Malinen <j@w1.fi>, Pkshih <pkshih@realtek.com>,
	"linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
	"ath10k@lists.infradead.org" <ath10k@lists.infradead.org>
Subject: Re: [PATCH 1/2] nl80211: vendor-cmd: qca: add dynamic SAR power limits
Date: Fri, 20 Mar 2020 13:55:58 +0100	[thread overview]
Message-ID: <e8908eafd8e6050eef8782c6a7019e318d14f65f.camel@sipsolutions.net> (raw)
In-Reply-To: <871rpqly6a.fsf@kamboji.qca.qualcomm.com> (sfid-20200317_175435_510355_7F89EC66)

On Tue, 2020-03-17 at 18:54 +0200, Kalle Valo wrote:

> For me either solutions are good enough, I'm not familiar enough with
> all the different SAR user space interfaces to make a good decision.

Brian probably has most insight into this :-)

I really didn't want to have to be the referee here, I was hoping you'd
figure this all out between yourselves... oh well.

But as somebody has said on one of these threads, there seem to
basically be two kinds of APIs:

 1) some kind of platform-dependent index into a table that the
    driver/device has, or perhaps the BIOS; and

 2) some kind of per-band (FSVO band) power restriction like here.


The first is like iwlwifi, and I think Marvell was mentioned? But
they're basically out - there's no information, and there's no clue as
to which indices might even be valid, I think, nor what they mean. So
there isn't really much value in a common API for that since you can't
use it in a common fashion - arguably a common API would be worse...


However, the case of 2, arguably the proposals are very similar?

Qualcomm: optional nl80211_band, 1/2 dBm units
Realtek: 2.4, four 5 GHz subbands, 1/4 dBm units

Both have some strange namespace thing where the same namespace contains
both the outer and inner attributes. Probably should think about the
policy with NLA_POLICY_NESTED and see how that works.


But it any case, these two don't seem like an insurmountable issue to
combine? Say, something like defining a list of affected frequency
ranges in the wiphy properties, and then giving a list of TX powers that
matches the list of frequency ranges? We can go to 1/4 dBm or so, that's
not such a big deal, I'd think?


On the other hand, what does that actually buy us? If you cannot have
common userspace that knows how a given platform must behave, then it's
not very worthwhile to have common API for it?

Brian, what do you think from a platform/userspace perspective - how do
you actually determine the SAR limits? I'm guessing you just have a
table of sorts, but how do you get the table? Would you actually have
common userspace and benefit from having common API?

johannes


WARNING: multiple messages have this Message-ID
From: Johannes Berg <johannes@sipsolutions.net>
To: Kalle Valo <kvalo@codeaurora.org>,
	Brian Norris <briannorris@chromium.org>
Cc: Jouni Malinen <j@w1.fi>, Pkshih <pkshih@realtek.com>,
	"linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
	"ath10k@lists.infradead.org" <ath10k@lists.infradead.org>
Subject: Re: [PATCH 1/2] nl80211: vendor-cmd: qca: add dynamic SAR power limits
Date: Fri, 20 Mar 2020 13:55:58 +0100	[thread overview]
Message-ID: <e8908eafd8e6050eef8782c6a7019e318d14f65f.camel@sipsolutions.net> (raw)
In-Reply-To: <871rpqly6a.fsf@kamboji.qca.qualcomm.com> (sfid-20200317_175435_510355_7F89EC66)

On Tue, 2020-03-17 at 18:54 +0200, Kalle Valo wrote:

> For me either solutions are good enough, I'm not familiar enough with
> all the different SAR user space interfaces to make a good decision.

Brian probably has most insight into this :-)

I really didn't want to have to be the referee here, I was hoping you'd
figure this all out between yourselves... oh well.

But as somebody has said on one of these threads, there seem to
basically be two kinds of APIs:

 1) some kind of platform-dependent index into a table that the
    driver/device has, or perhaps the BIOS; and

 2) some kind of per-band (FSVO band) power restriction like here.


The first is like iwlwifi, and I think Marvell was mentioned? But
they're basically out - there's no information, and there's no clue as
to which indices might even be valid, I think, nor what they mean. So
there isn't really much value in a common API for that since you can't
use it in a common fashion - arguably a common API would be worse...


However, the case of 2, arguably the proposals are very similar?

Qualcomm: optional nl80211_band, 1/2 dBm units
Realtek: 2.4, four 5 GHz subbands, 1/4 dBm units

Both have some strange namespace thing where the same namespace contains
both the outer and inner attributes. Probably should think about the
policy with NLA_POLICY_NESTED and see how that works.


But it any case, these two don't seem like an insurmountable issue to
combine? Say, something like defining a list of affected frequency
ranges in the wiphy properties, and then giving a list of TX powers that
matches the list of frequency ranges? We can go to 1/4 dBm or so, that's
not such a big deal, I'd think?


On the other hand, what does that actually buy us? If you cannot have
common userspace that knows how a given platform must behave, then it's
not very worthwhile to have common API for it?

Brian, what do you think from a platform/userspace perspective - how do
you actually determine the SAR limits? I'm guessing you just have a
table of sorts, but how do you get the table? Would you actually have
common userspace and benefit from having common API?

johannes


_______________________________________________
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ath10k@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/ath10k

  reply	other threads:[~2020-03-20 12:56 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-18 15:48 [PATCH 0/2] ath10k: SAR power limit vendor command Kalle Valo
2019-12-18 15:48 ` Kalle Valo
2019-12-18 15:48 ` [PATCH 1/2] nl80211: vendor-cmd: qca: add dynamic SAR power limits Kalle Valo
2019-12-18 15:48   ` Kalle Valo
2019-12-19  9:44   ` Pkshih
2019-12-19  9:44     ` Pkshih
2019-12-19 15:48     ` Jouni Malinen
2019-12-19 15:48       ` Jouni Malinen
2019-12-19 18:32       ` Brian Norris
2019-12-19 18:32         ` Brian Norris
2019-12-19 18:55         ` Jouni Malinen
2019-12-19 18:55           ` Jouni Malinen
2019-12-19 23:40           ` Brian Norris
2019-12-19 23:40             ` Brian Norris
2020-03-17 16:54             ` Kalle Valo
2020-03-17 16:54               ` Kalle Valo
2020-03-20 12:55               ` Johannes Berg [this message]
2020-03-20 12:55                 ` Johannes Berg
2020-06-02  1:32                 ` Brian Norris
2020-06-02  1:32                   ` Brian Norris
2020-07-16  9:35                   ` Kalle Valo
2020-07-16  9:35                     ` Kalle Valo
2020-07-16 18:56                     ` Brian Norris
2020-07-16 18:56                       ` Brian Norris
2020-07-24  9:26                       ` Kalle Valo
2020-07-24  9:26                         ` Kalle Valo
2020-07-30 13:24                         ` Johannes Berg
2020-07-30 13:24                           ` Johannes Berg
2020-08-01  1:31                           ` Brian Norris
2020-08-01  1:31                             ` Brian Norris
2020-09-08  5:55                           ` Kalle Valo
2020-09-08  5:55                           ` Kalle Valo
2020-07-30 13:17                   ` Johannes Berg
2020-07-30 13:17                     ` Johannes Berg
2019-12-18 15:48 ` [PATCH 2/2] ath10k: allow dynamic SAR power limits to be configured Kalle Valo
2019-12-18 15:48   ` Kalle Valo
2019-12-19  9:45   ` Pkshih
2019-12-19  9:45     ` Pkshih
2020-04-16  7:38   ` Kalle Valo
2020-04-16  7:38   ` Kalle Valo

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