linux-kernel - Re: [PATCH] Module argument to control whether intel-spi-pci attempts to turn the SPI flash chip writeable

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Date:   Sun, 26 Jul 2020 09:17:23 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Daniel Gutson <daniel@...ypsium.com>
Cc:     Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Boris Brezillon <bbrezillon@...nel.org>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Alex Bazhaniuk <alex@...ypsium.com>,
        Richard Hughes <hughsient@...il.com>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH] Module argument to control whether intel-spi-pci
 attempts to turn the SPI flash chip writeable

On Sat, Jul 25, 2020 at 02:20:03PM -0300, Daniel Gutson wrote:
> El sáb., 25 jul. 2020 2:56 a. m., Greg Kroah-Hartman <
> gregkh@...uxfoundation.org> escribió:
> 
> > On Fri, Jul 24, 2020 at 06:28:53PM -0300, Daniel Gutson wrote:
> > > Currently, intel-spi has a module argument that controls whether the
> > driver
> > > attempts to turn the SPI flash chip writeable. The default value
> > > is FALSE (don't try to make it writeable).
> > > However, this flag applies only for a number of devices, coming from the
> > > platform driver, whereas the devices detected through the PCI driver
> > > (intel-spi-pci) are not subject to this check since the configuration
> > > takes place in intel-spi-pci which doesn't have an argument.
> > >
> > > That's why I propose this patch to add such argument to intel-spi-pci,
> > > so the user can control whether the driver tries to make the chip
> > > writeable or not, being the default FALSE as is the argument of
> > > intel-spi.
> > >
> > > Signed-off-by: Daniel Gutson <daniel.gutson@...ypsium.com>
> > > ---
> > >  drivers/mtd/spi-nor/controllers/intel-spi-pci.c | 16 +++++++++++-----
> > >  1 file changed, 11 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/drivers/mtd/spi-nor/controllers/intel-spi-pci.c
> > b/drivers/mtd/spi-nor/controllers/intel-spi-pci.c
> > > index 81329f680bec..77e57450f166 100644
> > > --- a/drivers/mtd/spi-nor/controllers/intel-spi-pci.c
> > > +++ b/drivers/mtd/spi-nor/controllers/intel-spi-pci.c
> > > @@ -24,6 +24,10 @@ static const struct intel_spi_boardinfo cnl_info = {
> > >       .type = INTEL_SPI_CNL,
> > >  };
> > >
> > > +static bool writeable;
> > > +module_param(writeable, bool, 0);
> > > +MODULE_PARM_DESC(writeable, "Enable write access to SPI flash chip
> > (default=0)");
> >
> > Ick, this isn't the 1990's, please do not add new module parameters,
> > they are a major pain to work with and only work on a global basis, not
> > on a per-device basis.
> >
> > No user will remember how to use this, as it isn't documented anywhere
> > either.  Can you make this a sysfs attribute or something, or better
> > yet, make it "just work" depending on the device type?
> >
> 
> 1) I just did the same that intel-spi.c does.

No need to copy bad examples :)

> You need to understand that there's a set of DIDs coming from the
> lpc_ich (and then the platform) driver, and another set from
> intel-spi-pci. The first set is subject to the check, the second
> doesn't. So there is no "just work" as I understand it.

I have no idea what "DID" is here, sorry.

But why do you want to write it?

> 2) this is an initialization argument, I could make it always NOT attempt
> to make the chip writable, and a system attribute to turn it writable
> post-initialization but the behavior is not the same. In any ways, as I
> mentioned before, some DIDs will be covered by the existing argument of
> intel-spi and other DIDs by this sysfs attribute, becoming IMHO
> inconsistent from the user POV.

What sysfs attribute?  This is a module parameter :(

totally confused,

greg k-h