linux-kernel - Re: [PATCH v7 7/7] mtd: ubi: provide NVMEM layer over UBI volumes

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Date: Mon, 26 Feb 2024 00:05:40 +0000
From: Daniel Golle <daniel@...rotopia.org>
To: Richard Weinberger <richard@....at>
Cc: Miquel Raynal <miquel.raynal@...tlin.com>,
	Vignesh Raghavendra <vigneshr@...com>,
	Rob Herring <robh+dt@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>,
	linux-mtd <linux-mtd@...ts.infradead.org>,
	devicetree <devicetree@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 7/7] mtd: ubi: provide NVMEM layer over UBI volumes

Hi Richard,

On Sun, Feb 25, 2024 at 11:12:54PM +0100, Richard Weinberger wrote:
> ----- Ursprüngliche Mail -----
> > Von: "Miquel Raynal" <miquel.raynal@...tlin.com>
> > An: "Daniel Golle" <daniel@...rotopia.org>
> > CC: "richard" <richard@....at>, "Vignesh Raghavendra" <vigneshr@...com>, "Rob Herring" <robh+dt@...nel.org>, "Krzysztof
> > Kozlowski" <krzysztof.kozlowski+dt@...aro.org>, "Conor Dooley" <conor+dt@...nel.org>, "linux-mtd"
> > <linux-mtd@...ts.infradead.org>, "devicetree" <devicetree@...r.kernel.org>, "linux-kernel"
> > <linux-kernel@...r.kernel.org>
> > Gesendet: Montag, 19. Februar 2024 12:01:56
> > Betreff: Re: [PATCH v7 7/7] mtd: ubi: provide NVMEM layer over UBI volumes
> 
> > Hi Daniel,
> > 
> > daniel@...rotopia.org wrote on Tue, 19 Dec 2023 02:33:48 +0000:
> > 
> >> In an ideal world we would like UBI to be used where ever possible on a
> >> NAND chip. And with UBI support in ARM Trusted Firmware and U-Boot it
> >> is possible to achieve an (almost-)all-UBI flash layout. Hence the need
> >> for a way to also use UBI volumes to store board-level constants, such
> >> as MAC addresses and calibration data of wireless interfaces.
> >> 
> >> Add UBI volume NVMEM driver module exposing UBI volumes as NVMEM
> >> providers. Allow UBI devices to have a "volumes" firmware subnode with
> >> volumes which may be compatible with "nvmem-cells".
> >> Access to UBI volumes via the NVMEM interface at this point is
> >> read-only, and it is slow, opening and closing the UBI volume for each
> >> access due to limitations of the NVMEM provider API.
> > 
> > I don't feel qualified enough to review the other patches, however this
> > one looks good to me.
> 
> Finally(!), I had enough time to look.
> Thanks for addressing all my comments form the previous series.
> Patches applied.

It's an enourmous coicident that you are writing just now that I found
a sizeof(int)-related problem which triggers a compiler warning when
building the UBI NVMEM provider on 32-bit platforms. I was just about
to prepare an updated series. Literally in this minute.
Should I still send the whole updates series or only the final patch
(as the necessary change is there) or a follow-up patch fixing the
original patch?

> 
> I have only one tiny request, can you share the lockdep spalt
> you encountered in ubi_notify_add() regarding mtd_table_mutex
> and ubi_devices_mutex? The solutions looks okay to me, but
> if you have more details that would be great.

I will setup a test build to reproduce the original warning and
let you know shortly.


Cheers


Daniel