linux-kernel - Re: [PATCH v8 10/22] counter: Standardize to ERANGE for limit exceeded errors

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Date:   Sun, 21 Feb 2021 14:03:12 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     William Breathitt Gray <vilhelm.gray@...il.com>
Cc:     kernel@...gutronix.de, linux-stm32@...md-mailman.stormreply.com,
        a.fatoum@...gutronix.de, kamel.bouhara@...tlin.com,
        gwendal@...omium.org, alexandre.belloni@...tlin.com,
        david@...hnology.com, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        syednwaris@...il.com, patrick.havelange@...ensium.com,
        fabrice.gasnier@...com, mcoquelin.stm32@...il.com,
        alexandre.torgue@...com, o.rempel@...gutronix.de
Subject: Re: [PATCH v8 10/22] counter: Standardize to ERANGE for limit
 exceeded errors

On Tue, 16 Feb 2021 10:26:52 +0900
William Breathitt Gray <vilhelm.gray@...il.com> wrote:

> On Sun, Feb 14, 2021 at 05:10:21PM +0000, Jonathan Cameron wrote:
> > On Fri, 12 Feb 2021 21:13:34 +0900
> > William Breathitt Gray <vilhelm.gray@...il.com> wrote:
> >   
> > > ERANGE is a semantically better error code to return when an argument
> > > value falls outside the supported limit range of a device.  
> > 
> > #define	ERANGE		34	/* Math result not representable */
> > 
> > Not generally applicable to a parameter being out of range
> > despite the name.
> > #define	EINVAL		22	/* Invalid argument */
> > Is probably closer to what we want to describe here.
> > 
> > Jonathan  
> 
> The comment for ERANGE in error-base.h may be terse to a fault. I
> believe there's a connotation here provided by ERANGE that is absent
> from EINVAL: primarily that the device buffer is incapable of supporting
> the desired value (i.e. there is a hardware limitation).
> 
> This is why strtoul() returns ERANGE if the correct value is outside the
> range of representable values: the result of the operation is valid in
> theory (it would be an unsigned integer), but it cannot be returned to
> the user due to a limitation of the hardware to support that value (e.g.
> 32-bit registers) [1].
> 
> The changes in this patch follow the same logic: these are arguments
> that are valid in theory (e.g. they are unsigned integers), but the
> underlying devices are incapable of processing such a value (e.g. the
> 104-QUAD-8 can only handle 24-bit values).
> 
> [1] https://stackoverflow.com/a/34981398/1806289

Its a bit of a stretch, but I can't claim to feel that strongly about
this.

Jonathan

> 
> William Breathitt Gray