Re: [PATCH 06/11] net: dsa: ksz9477: create regmap cdev for switch registers

[Sascha Hauer <sha@pengutronix.de>]

On Wed, Jan 11, 2023 at 09:01:14AM +0100, Ahmad Fatoum wrote:
> Now that we use regmap for the KSZ9477 driver, we can make the register
> map available for introspection as a device file. As the KSZ driver has
> a separate regmap for each of the three access sizes, we add a new
> regmap_multi_register_cdev abstraction that multiplexes device file
> access to the regmap with the best matching alignment.
> 
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> ---
>  drivers/base/regmap/Makefile       |  1 +
>  drivers/base/regmap/regmap-multi.c | 81 ++++++++++++++++++++++++++++++
>  drivers/net/ksz9477.c              |  6 ++-
>  include/regmap.h                   |  2 +
>  4 files changed, 89 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/base/regmap/regmap-multi.c
> 
> diff --git a/drivers/base/regmap/Makefile b/drivers/base/regmap/Makefile
> index d99db4277149..fe5beaaaa382 100644
> --- a/drivers/base/regmap/Makefile
> +++ b/drivers/base/regmap/Makefile
> @@ -1,5 +1,6 @@
>  # SPDX-License-Identifier: GPL-2.0-only
>  obj-y	+= regmap.o
> +obj-y	+= regmap-multi.o
>  obj-y	+= regmap-mmio.o
>  obj-$(CONFIG_REGMAP_FORMATTED)	+= regmap-fmt.o
>  obj-$(CONFIG_I2C)	+= regmap-i2c.o
> diff --git a/drivers/base/regmap/regmap-multi.c b/drivers/base/regmap/regmap-multi.c
> new file mode 100644
> index 000000000000..79dd1ba9bd95
> --- /dev/null
> +++ b/drivers/base/regmap/regmap-multi.c
> @@ -0,0 +1,81 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright 2022 Ahmad Fatoum <a.fatoum@pengutronix.de>
> + */
> +
> +#include <common.h>
> +#include <regmap.h>
> +#include <linux/export.h>
> +
> +#include "internal.h"
> +
> +enum { MULTI_MAP_8, MULTI_MAP_16, MULTI_MAP_32, MULTI_MAP_COUNT };
> +struct regmap_multi {
> +	struct cdev cdev;
> +	struct regmap *map[MULTI_MAP_COUNT];
> +};
> +
> +static struct regmap *regmap_multi_cdev_get_map(struct cdev *cdev, size_t count)
> +{
> +	struct regmap_multi *multi = container_of(cdev, struct regmap_multi, cdev);
> +	struct regmap *map = NULL;
> +
> +	if (count % 4 == 0)
> +		map = multi->map[MULTI_MAP_32];
> +	if (!map && count % 2 == 0)
> +		map = multi->map[MULTI_MAP_16];
> +	return map ?: multi->map[MULTI_MAP_8];
> +}

You pick the regmap only based on 'count'. Shouldn't you take the offset
into account as well?

> +
> +static ssize_t regmap_multi_cdev_read(struct cdev *cdev, void *buf, size_t count,
> +				      loff_t offset, unsigned long flags)
> +{
> +	struct regmap *map = regmap_multi_cdev_get_map(cdev, count);
> +
> +	return regmap_bulk_read(map, offset, buf, count) ?: count;
> +}
> +
> +static ssize_t regmap_multi_cdev_write(struct cdev *cdev, const void *buf, size_t count,
> +				       loff_t offset, unsigned long flags)
> +{
> +	struct regmap *map = regmap_multi_cdev_get_map(cdev, count);
> +
> +	return regmap_bulk_write(map, offset, buf, count) ?: count;
> +}
> +
> +static struct cdev_operations regmap_multi_fops = {
> +	.read	= regmap_multi_cdev_read,
> +	.write	= regmap_multi_cdev_write,
> +};
> +
> +int regmap_multi_register_cdev(struct regmap *maps[3])

MULTI_MAP_COUNT instead of 3?

Sascha

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