linux-kernel - Re: [PATCH 3/5] firmware: revamp firmware documentation

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Message-ID: <1481880850.27953.12.camel@sipsolutions.net>
Date:   Fri, 16 Dec 2016 10:34:10 +0100
From:   Johannes Berg <johannes@...solutions.net>
To:     "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Rafał Miłecki <zajec5@...il.com>
Cc:     Daniel Wagner <daniel.wagner@...-carit.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ming Lei <ming.lei@...onical.com>, Tom Gundersen <teg@...m.no>,
        Mauro Carvalho Chehab <mchehab@....samsung.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Vikram Mulukutla <markivx@...eaurora.org>,
        Stephen Boyd <stephen.boyd@...aro.org>,
        Mark Brown <broonie@...nel.org>, zohar@...ux.vnet.ibm.com,
        Takashi Iwai <tiwai@...e.de>,
        Christian Lamparter <chunkeey@...glemail.com>,
        Hauke Mehrtens <hauke@...ke-m.de>,
        Josh Boyer <jwboyer@...oraproject.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        David Woodhouse <dwmw2@...radead.org>, jslaby@...e.com,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        luto@...capital.net, Fengguang Wu <fengguang.wu@...el.com>,
        Richard Purdie <rpurdie@...ys.net>,
        Jacek Anaszewski <j.anaszewski@...sung.com>,
        Abhay_Salunke@...l.com, Julia Lawall <Julia.Lawall@...6.fr>,
        Gilles.Muller@...6.fr, nicolas.palix@...g.fr, dhowells@...hat.com,
        bjorn.andersson@...aro.org,
        Arend Van Spriel <arend.vanspriel@...adcom.com>,
        Kalle Valo <kvalo@...eaurora.org>
Subject: Re: [PATCH 3/5] firmware: revamp firmware documentation

> > > Maybe it is worth to mention, that the calibration data is unique
> > > to a given chip, so it is individual. That is you would need to
> > > built for each device you sell its own kernel.
> > 
> > It's commonly unique to the device model, not a chip. The same chip
> > can be used with different power amplifiers or different antennas.
> > That's why you need model (board) specific calibration data.
> 
> From what I recall in my 802.11 days this can be often very specific
> per *batch* of cards not just chip/device model, so this depends on
> the manufacturing process and date.

Yes, it can be a per-device calibration done in the factory, and then
the data is programmed into the device after that calibration - but if
the device is something like a router (not a standalone NIC) then the
data might still go through request_firmware() or similar in the end.

johannes