linux-kernel - Re: [PATCH] mtd: spi-nor: intel-spi: Do not try to make the SPI flash chip writable

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Date:   Mon, 24 Aug 2020 11:08:33 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:     Daniel Gutson <daniel@...ypsium.com>,
        Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Boris Brezillon <bbrezillon@...nel.org>,
        linux-mtd <linux-mtd@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Alex Bazhaniuk <alex@...ypsium.com>,
        Richard Hughes <hughsient@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] mtd: spi-nor: intel-spi: Do not try to make the SPI flash
 chip writable

On Mon, Aug 24, 2020 at 10:22 AM Mika Westerberg
<mika.westerberg@...ux.intel.com> wrote:
> On Sat, Aug 22, 2020 at 06:06:03PM +0200, Arnd Bergmann wrote:
> > On Wed, Aug 19, 2020 at 11:11 AM Mika Westerberg
> >
> > The mtd core just checks both the permissions on the device node (which
> > default to 0600 without any special udev rules) and the MTD_WRITEABLE
> > on the underlying device that is controlled by the module parameter
> > in case of intel-spi{,-platform,-pci}.c.
>
> OK, thanks.
>
> Since we cannot really get rid of the module parameter (AFAIK there are
> users for it), I still think we should just make the "writeable" to
> apply to the PCI part as well. That should at least make it consistent,
> and it also solves Daniel's case.

Can you explain Daniel's case then? I still don't understand what he
actually wants.

As I keep repeating, the module parameter *does* apply to the pci
driver front-end since it determines whether the driver will disallow
writes to the mtd device without it. The only difference is that the pci
driver will attempt to set the hardware bit without checking the
module parameter first, while the platform driver does not. If the
module parameter is not set however, the state of the hardware
bit is never checked again.

    Arnd