linux-kernel - Re: [PATCH v2 3/4] iio: light: veml3235: extend regmap to add cache

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Message-Id: <D7082ZE34NTT.DHC0Y5220527@gmail.com>
Date: Sun, 12 Jan 2025 17:07:41 +0100
From: "Javier Carrasco" <javier.carrasco.cruz@...il.com>
To: "Andy Shevchenko" <andy.shevchenko@...il.com>
Cc: "Matti Vaittinen" <mazziesaccount@...il.com>, "Jonathan Cameron"
 <jic23@...nel.org>, "Lars-Peter Clausen" <lars@...afoo.de>,
 <linux-iio@...r.kernel.org>, <linux-kernel@...r.kernel.org>, "Jonathan
 Cameron" <Jonathan.Cameron@...wei.com>
Subject: Re: [PATCH v2 3/4] iio: light: veml3235: extend regmap to add cache

On Sun Jan 12, 2025 at 4:18 PM CET, Andy Shevchenko wrote:
> Tue, Dec 24, 2024 at 11:59:02AM +0100, Javier Carrasco kirjoitti:
> > The configuration and ID registers are not volatile and are not affected
> > by read operations (i.e. not precious), making them suitable to be
> > cached in order to reduce the number of accesses to the device.
>
> ...
>
> >  static const struct regmap_config veml3235_regmap_config = {
> >  	.name = "veml3235_regmap",
> >  	.reg_bits = 8,
> >  	.val_bits = 16,
> >  	.max_register = VEML3235_REG_ID,
> >  	.val_format_endian = REGMAP_ENDIAN_LITTLE,
> > +	.rd_table = &veml3235_readable_table,
> > +	.wr_table = &veml3235_writable_table,
> > +	.volatile_table = &veml3235_volatile_table,
> > +	.cache_type = REGCACHE_RBTREE,
>
> Any specific reason why this is NOT a maple tree?
>

Hello Andy,

I followed the most common approach in IIO (52 RBTREE vs 2 MAPLE),
assuming that the "low-end systems" comment for the different REGCACHE_*
applies well to the typical systems that will make use of this driver,
and many others under IIO. I considered that *possible* performance
advantage for low-end systems above other considerations, like the
general rule about using maple tree.

Thanks and best regards,
Javier Carrasco