linux-kernel - Re: [PATCH v3 3/6] mfd: cs42l43: Add support for cs42l43 core driver

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Message-ID: <20230619085244.GU68926@ediswmail.ad.cirrus.com>
Date:   Mon, 19 Jun 2023 08:52:44 +0000
From:   Charles Keepax <ckeepax@...nsource.cirrus.com>
To:     Lee Jones <lee@...nel.org>
CC:     <broonie@...nel.org>, <krzysztof.kozlowski+dt@...aro.org>,
        <linus.walleij@...aro.org>, <vkoul@...nel.org>,
        <robh+dt@...nel.org>, <conor+dt@...nel.org>, <lgirdwood@...il.com>,
        <yung-chuan.liao@...ux.intel.com>, <sanyog.r.kale@...el.com>,
        <pierre-louis.bossart@...ux.intel.com>,
        <alsa-devel@...a-project.org>, <patches@...nsource.cirrus.com>,
        <devicetree@...r.kernel.org>, <linux-gpio@...r.kernel.org>,
        <linux-spi@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 3/6] mfd: cs42l43: Add support for cs42l43 core driver

On Mon, Jun 19, 2023 at 09:30:05AM +0100, Lee Jones wrote:
> On Fri, 16 Jun 2023, Charles Keepax wrote:
> > On Thu, Jun 15, 2023 at 06:11:24PM +0100, Lee Jones wrote:
> > > On Mon, 05 Jun 2023, Charles Keepax wrote:
> > > > +static struct i2c_device_id cs42l43_i2c_id[] = {
> > > > +	{ "cs42l43", 0 },
> > > > +	{}
> > > > +};
> > > > +MODULE_DEVICE_TABLE(i2c, cs42l43_i2c_id);
> > > 
> > > Is this required anymore?
> > > 
> > 
> > I was not aware of it not being required, I think it will still
> > be used for the purposes of module naming. Perhaps someone more
> > knowledgable than me can comment?
> 
> Since this table isn't providing any information which cannot be derived
> from the other (OF, ACPI) tables, the I2C subsystem should be able to
> obtain it from those sources instead.
> 

Sorry I literally just sent a v4 then saw this email. I will test
removing this table and send a v5.

> > > > +#if IS_ENABLED(CONFIG_MFD_CS42L43_I2C)
> > > > +const struct regmap_config cs42l43_i2c_regmap = {
> > > > +	.reg_bits		= 32,
> > > > +	.reg_stride		= 4,
> > > > +	.val_bits		= 32,
> > > > +	.reg_format_endian	= REGMAP_ENDIAN_BIG,
> > > > +	.val_format_endian	= REGMAP_ENDIAN_BIG,
> > > > +
> > > > +	.max_register		= CS42L43_MCU_RAM_MAX,
> > > > +	.readable_reg		= cs42l43_readable_register,
> > > > +	.volatile_reg		= cs42l43_volatile_register,
> > > > +	.precious_reg		= cs42l43_precious_register,
> > > > +
> > > > +	.cache_type		= REGCACHE_RBTREE,
> > > > +	.reg_defaults		= cs42l43_reg_default,
> > > > +	.num_reg_defaults	= ARRAY_SIZE(cs42l43_reg_default),
> > > > +};
> > > > +EXPORT_SYMBOL_NS_GPL(cs42l43_i2c_regmap, MFD_CS42L43);
> > > > +#endif
> > > 
> > > We don't tend to like #ifery in C files.
> > > 
> > > Why is it required?
> > > 
> > > And why not just put them were they're consumed?
> > 
> > The trouble is the cs42l43_reg_default array and the array size.
> > There is no good way to statically initialise those two fields
> > from a single array in both the I2C and SDW modules.
> 
> Can you have a little think for another way to solve this please?
> 

I will have another go at it, if memory serves the vague options
were:

1) this approach
2) some sort of horrible #include to put the defaults array in
both modules, although I would really prefer to avoid this one.
3) dynamically allocate the regmap_configs so those two fields
can be filled in with non-static data.

If I fail to come up with an option 4 would you prefer 1 or 3?
Well or 2 but I really would prefer not to do 2.

> > > Perhaps some simple function headers would help?
> > You mean add some kernel doc for these functions, right? Assuming
> > that is what you mean, will do.
> 
> I'd suggest not using kernel-doc formatting, but that type of thing,
> yes.

Ok I will remove the kernel doc bits for v5.

Thanks,
Charles