Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Mon, 17 Jul 2023 18:41:17 +0200
From:   Miquel Raynal <miquel.raynal@bootlin.com>
To:     Michael Walle <michael@walle.cc>
Cc:     Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel@vger.kernel.org,
        Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
        Robert Marko <robert.marko@sartura.hr>,
        Luka Perkov <luka.perkov@sartura.hr>,
        Randy Dunlap <rdunlap@infradead.org>
Subject: Re: [PATCH v6 3/3] nvmem: core: Expose cells through sysfs
Message-ID: <20230717184117.065e9585@xps-13>
In-Reply-To: <f85f117a59586dc2e5df33e11b39c69f@walle.cc>
References: <20230717075147.43326-1-miquel.raynal@bootlin.com>
        <20230717075147.43326-4-miquel.raynal@bootlin.com>
        <f85f117a59586dc2e5df33e11b39c69f@walle.cc>
Organization: Bootlin
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

Hi Michael,

michael@walle.cc wrote on Mon, 17 Jul 2023 14:24:45 +0200:

> Hi,
>=20
> > There is one limitation though: if a layout is built as a module but is
> > not properly installed in the system and loaded manually with insmod
> > while the nvmem device driver was built-in, the cells won't appear in
> > sysfs. But if done like that, the cells won't be usable by the built-in
> > kernel drivers anyway. =20
>=20
> What is the difference between manual loading with insmod and automatic
> module loading? Or is the limitation, layout as M and device driver as Y
> doesn't work?

The nvmem core uses usermodehelper to load the relevant layout
module, but that only works if the module was installed correctly (make
modules_install).

The limitation is:
* Any storage device driver that registers an nvmem interface =3Dy (or =3Dm
  but loaded before the nvmem layout)
* The relevant nvmem layout =3Dm *and* not installed with make
  modules_install

If you see a way to workaround this, let me know, but there is no way
we can enforce Kconfig dependencies between storage drivers and nvmem
layouts IMHO.

Thanks,
Miqu=C3=A8l