Return-path: Received: from mx1.redhat.com ([209.132.183.28]:51857 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751383AbcF3Jx3 (ORCPT ); Thu, 30 Jun 2016 05:53:29 -0400 Subject: Re: [linux-sunxi] Re: [PATCH 1/4] brcmfmac: Add brcm,nvram_file_name dt property To: Arend Van Spriel , Kalle Valo References: <1467209074-15634-1-git-send-email-hdegoede@redhat.com>

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Cc: Jonas Gorski , "John W . Linville" , Arend van Spriel , Maxime Ripard , Chen-Yu Tsai , "linux-wireless@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , devicetree , linux-sunxi@googlegroups.com From: Hans de Goede Message-ID: (sfid-20160630_115333_228232_58E5BAEB) Date: Thu, 30 Jun 2016 11:53:21 +0200 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Sender: linux-wireless-owner@vger.kernel.org List-ID: Hi, On 29-06-16 20:51, 'Arend Van Spriel' via linux-sunxi wrote: > On 29-6-2016 20:01, Hans de Goede wrote: >> Hi, >> >> On 29-06-16 19:00, Kalle Valo wrote: >>> Hans de Goede writes: >>> >>>> Hi, >>>> >>>> On 29-06-16 16:42, Jonas Gorski wrote: >>>>> Hi, >>>>> >>>>> On 29 June 2016 at 16:04, Hans de Goede wrote: >>>>>> Add a brcm,nvram_file_name dt property to allow overruling the default >>>>>> nvram filename for sdio devices. The idea is that we can specify a >>>>>> board specific nvram file, e.g. brcmfmac43362-ap6210.txt for boards >>>>>> with an ap6210 wifi sdio module and ship this in linux-firmware, so >>>>>> that wifi will work out of the box, without requiring users to find >>>>>> and then manually install the right nvram file for their board. >>>>> >>>>> Directly defining a filename doesn't seem like a good OS-agnostic >>>>> approach. Maybe an alternative would be to add a model-property to the >>>>> nodes (this is allowed) and make brcmfmac to request >>>>> "FWFILENAME-" as firmware if set? That would leave it to the OS >>>>> on how the filename is set. >>>> >>>> It only defines the base-filename, not the entire path, how / where >>>> this file is searched for / loaded-from is then left up to the os >>> >>> It's still a bad idea. The filename, including the path, should be >>> created in the driver. Can't you provide chipname (or similar) via >>> device tree and then the driver can choose what image to use? >> >> No, the driver already does that, but this is not ... >> >>> Can you tell more about the naming the firmware image, how does it work >>> exactly? >> >> About firmware, this is about the nvram file which is board specific, >> rather then chip specific. > > The nvram filename is determined pretty much the same as the firmware > filename, but indeed the nvram data is board specific. This is main > reason why we do not submit nvram files to linux-firmware, because we > simply do not have those files. > >> Typical wifi devices will have some sort of non volatile storage >> on board to not only store the ethernet(mac) address, but also >> to contain e.g. info about the antenna gain so that the firmware >> and/or the driver can take the antenna gain into account and ensure >> that they never exceed the maximum allowed broadcast strength. >> >> However on some embedded devices there is no non-volatile storage >> for the wifi (for cost reasons) and instead this configuration info >> (which is board / pcb specific) is loaded in the form of a >> file which contains the contents which would normally be in the >> non-volatile storage. >> >> Since we are dealing with a per-board config-file here, which is >> loaded from the os filesystem we really need to specify a basename >> here as the list of possible boards is endless, so we cannot >> have a lookup table in the driver. > > As Jonas mentioned the general principle of device tree is to be > agnostic with regards to OS and/or driver as you undoubtedly know. His > proposal seems like a usable solution for your problem while complying > to the device tree principle. So instead of overriding the default > brcmfmac should modify it when dt specifies the "module" property, ie: > > no "module" in DT: nvram filename = brcm/brcmfmac43362-sdio.txt > "module=ap6210" in DT: nvram filename = brcm/brcmfmac43362-ap6210.txt Yes that seems like a good solution, I will send a v2 implementing this. > By the way, the example in the bindings file does not seem to specify a > basename, but path+basename+fileext. fileext is always part of a file basename, but you're right that it does include a relative path because of the way the existing firmware files are organized under /lib/firmware under Linux and yes I'll admit that that is a bit os specific :) Regards, Hans