linux-kernel - Re: [PATCH v2,5/5] drivers: uio: new driver for fsl_85xx_cache

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Message-ID: <85bb4c9563377d2f76938ff1419ba34a5c825c0c.camel@buserror.net>
Date:   Thu, 16 Apr 2020 14:36:09 -0500
From:   Scott Wood <oss@...error.net>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Christophe Leroy <christophe.leroy@....fr>,
        Wang Wenhu <wenhu.wang@...o.com>, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, kernel@...o.com,
        Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH v2,5/5] drivers: uio: new driver for fsl_85xx_cache_sram

On Thu, 2020-04-16 at 08:30 +0200, Greg KH wrote:
> On Wed, Apr 15, 2020 at 02:27:51PM -0500, Scott Wood wrote:
> > > > +		dev_err(&pdev->dev, "error no valid uio-map
> > > > configured\n");
> > > > +		ret = -EINVAL;
> > > > +		goto err_info_free_internel;
> > > > +	}
> > > > +
> > > > +	info->version = "0.1.0";
> > > 
> > > Could you define some DRIVER_VERSION in the top of the file next to 
> > > DRIVER_NAME instead of hard coding in the middle on a function ?
> > 
> > That's what v1 had, and Greg KH said to remove it.  I'm guessing that he
> > thought it was the common-but-pointless practice of having the driver
> > print a
> > version number that never gets updated, rather than something the UIO API
> > (unfortunately, compared to a feature query interface) expects.  That
> > said,
> > I'm not sure what the value is of making it a macro since it should only
> > be
> > used once, that use is self documenting, it isn't tunable, etc.  Though if
> > this isn't a macro, UIO_NAME also shouldn't be (and if it is made a macro
> > again, it should be UIO_VERSION, not DRIVER_VERSION).
> > 
> > Does this really need a three-part version scheme?  What's wrong with a
> > version of "1", to be changed to "2" in the hopefully-unlikely event that
> > the
> > userspace API changes?  Assuming UIO is used for this at all, which
> > doesn't
> > seem like a great fit to me.
> 
> No driver version numbers at all please, they do not make any sense when
> the driver is included in the kernel tree.

Again, reporting a version string is part of the UIO API.  It might not be a
good API, but if it's left as NULL the registration will fail.

-Scott