linux-kernel - Re: [PATCH v2 2/3] counter: 104-quad-8: Refactor to buffer states for CMR, IOR, and IDR

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Date:   Fri, 24 Mar 2023 15:48:19 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     William Breathitt Gray <william.gray@...aro.org>
Cc:     linux-iio@...r.kernel.org, Johannes Berg <johannes.berg@...el.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] counter: 104-quad-8: Refactor to buffer states
 for CMR, IOR, and IDR

On Fri, Mar 24, 2023 at 09:26:14AM -0400, William Breathitt Gray wrote:
> On Fri, Mar 24, 2023 at 01:50:07PM +0200, Andy Shevchenko wrote:
> > On Fri, Mar 24, 2023 at 01:48:43PM +0200, Andy Shevchenko wrote:
> > > On Thu, Mar 23, 2023 at 05:25:28PM -0400, William Breathitt Gray wrote:

...

> > > > +static void quad8_control_register_update(struct quad8 *const priv, u8 *const buf,
> > > > +					  const size_t channel, const u8 val, const u8 field)
> > > > +{
> > > > +	u8p_replace_bits(&buf[channel], val, field);
> > > > +	iowrite8(buf[channel], &priv->reg->channel[channel].control);
> > > > +}
> > > 
> > > How did you compile this?
> > > Due to nature of *_replace_bits() this may only be a macro.
> > > 
> > > That's what LKP is telling about I think.
> > 
> > Ah, no, that's because the last parameter is not constant in the last patch in
> > the series.

> I'm having trouble cross-compiling for riscv, but I'm unable to recreate
> the build error when I compile for x86_64. However, I'd like to
> understand this error so I can fix it properly.
> 
> Is the problem here due to the "const u8 field" parameter? Instead of a
> constant variable, does this need to be a constant literal value for
> u8p_replace_bits()? I don't think that parameter changed in the last
> patch of the series, so why is the build error occurring for the last
> patch and not this penultimate patch here?

Good question. Perhaps my understanding is incorrect.

> Would qualifying the
> quad8_control_register_update() function with "__always_inline" resolve
> this issue?

Hmm... Don't know. You can always download a toolchain specifically build for
building kernels: https://mirrors.edge.kernel.org/pub/tools/crosstool/.

-- 
With Best Regards,
Andy Shevchenko