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Sender: Guenter Roeck <groeck7@gmail.com>
Date:   Wed, 12 Apr 2023 08:33:19 -0700
From:   Guenter Roeck <linux@roeck-us.net>
To:     Lakshmi Yadlapati <lakshmiy@us.ibm.com>
Cc:     robh+dt@kernel.org, jdelvare@suse.com,
        krzysztof.kozlowski+dt@linaro.org, joel@jms.id.au, andrew@aj.id.au,
        eajames@linux.ibm.com, linux-kernel@vger.kernel.org,
        linux-hwmon@vger.kernel.org, devicetree@vger.kernel.org
Subject: Re: [PATCH v6 3/5] hwmon: (pmbus/acbel-fsg032) Add Acbel power supply
Message-ID: <31bff772-b005-4aeb-85b8-ecd5b6847907@roeck-us.net>
References: <20230412052305.1369521-1-lakshmiy@us.ibm.com>
 <20230412052305.1369521-4-lakshmiy@us.ibm.com>
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In-Reply-To: <20230412052305.1369521-4-lakshmiy@us.ibm.com>
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On Wed, Apr 12, 2023 at 12:23:03AM -0500, Lakshmi Yadlapati wrote:
> Add the driver to support ACBEL FSG032 power supply.
> 
> Change-Id: Ief984325fe3fa0ed042e1d00e34ff579b45e1c81
> Signed-off-by: Lakshmi Yadlapati <lakshmiy@us.ibm.com>
> ---
>  drivers/hwmon/pmbus/Kconfig        |  9 +++
>  drivers/hwmon/pmbus/Makefile       |  1 +
>  drivers/hwmon/pmbus/acbel-fsg032.c | 95 ++++++++++++++++++++++++++++++
>  3 files changed, 105 insertions(+)
>  create mode 100644 drivers/hwmon/pmbus/acbel-fsg032.c
> 
> diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
> index 59d9a7430499..270b6336b76d 100644
> --- a/drivers/hwmon/pmbus/Kconfig
> +++ b/drivers/hwmon/pmbus/Kconfig
> @@ -27,6 +27,15 @@ config SENSORS_PMBUS
>  	  This driver can also be built as a module. If so, the module will
>  	  be called pmbus.
>  
> +config SENSORS_ACBEL_FSG032
> +	tristate "ACBEL FSG032 Power Supply"
> +	help
> +	  If you say yes here you get hardware monitoring support for the ACBEL
> +	  FSG032 Power Supply.
> +
> +	  This driver can also be built as a module. If so, the module will
> +	  be called acbel-fsg032.
> +
>  config SENSORS_ADM1266
>  	tristate "Analog Devices ADM1266 Sequencer"
>  	select CRC8
> diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
> index 3ae019916267..84ee960a6c2d 100644
> --- a/drivers/hwmon/pmbus/Makefile
> +++ b/drivers/hwmon/pmbus/Makefile
> @@ -5,6 +5,7 @@
>  
>  obj-$(CONFIG_PMBUS)		+= pmbus_core.o
>  obj-$(CONFIG_SENSORS_PMBUS)	+= pmbus.o
> +obj-$(CONFIG_SENSORS_ACBEL_FSG032) += acbel-fsg032.o
>  obj-$(CONFIG_SENSORS_ADM1266)	+= adm1266.o
>  obj-$(CONFIG_SENSORS_ADM1275)	+= adm1275.o
>  obj-$(CONFIG_SENSORS_BEL_PFE)	+= bel-pfe.o
> diff --git a/drivers/hwmon/pmbus/acbel-fsg032.c b/drivers/hwmon/pmbus/acbel-fsg032.c
> new file mode 100644
> index 000000000000..f160f45c7ac5
> --- /dev/null
> +++ b/drivers/hwmon/pmbus/acbel-fsg032.c
> @@ -0,0 +1,95 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright 2023 IBM Corp.
> + */
> +
> +#include <linux/debugfs.h>
> +#include <linux/device.h>
> +#include <linux/fs.h>
> +#include <linux/i2c.h>
> +#include <linux/module.h>
> +#include <linux/pmbus.h>
> +#include <linux/hwmon-sysfs.h>
> +#include "pmbus.h"
> +
> +static const struct i2c_device_id acbel_fsg032_id[] = {
> +	{ "acbel_fsg032" },
> +	{}
> +};
> +
> +static struct pmbus_driver_info acbel_fsg032_info = {
> +	.pages = 1,
> +	.func[0] = PMBUS_HAVE_VIN | PMBUS_HAVE_IIN | PMBUS_HAVE_PIN |
> +		   PMBUS_HAVE_VOUT | PMBUS_HAVE_IOUT | PMBUS_HAVE_POUT |
> +		   PMBUS_HAVE_TEMP | PMBUS_HAVE_TEMP2 | PMBUS_HAVE_TEMP3 |
> +		   PMBUS_HAVE_FAN12 | PMBUS_HAVE_STATUS_VOUT |
> +		   PMBUS_HAVE_STATUS_IOUT | PMBUS_HAVE_STATUS_TEMP |
> +		   PMBUS_HAVE_STATUS_INPUT | PMBUS_HAVE_STATUS_FAN12,
> +};
> +
> +static int acbel_fsg032_probe(struct i2c_client *client)
> +{
> +	u8 buf[I2C_SMBUS_BLOCK_MAX + 1];
> +	struct device *dev = &client->dev;
> +	struct dentry *debugfs;
> +	int rc;
> +
> +	rc = i2c_smbus_read_block_data(client, PMBUS_MFR_ID, buf);
> +	if (rc < 0) {
> +		dev_err(dev, "Failed to read PMBUS_MFR_ID\n");
> +		return rc;
> +	}
> +	if (strncmp(buf, "ACBEL", 5)) {
> +		buf[rc] = '\0';
> +		dev_err(dev, "Manufacturer '%s' not supported\n", buf);
> +		return -ENODEV;
> +	}
> +
> +	rc = i2c_smbus_read_block_data(client, PMBUS_MFR_MODEL, buf);
> +	if (rc < 0) {
> +		dev_err(dev, "Failed to read PMBUS_MFR_MODEL\n");
> +		return rc;
> +	}
> +
> +	if (strncmp(buf, "FSG032", 6)) {
> +		buf[rc] = '\0';
> +		dev_err(dev, "Model '%s' not supported\n", buf);
> +		return -ENODEV;
> +	}
> +
> +	rc = pmbus_do_probe(client, &acbel_fsg032_info);
> +	if (rc)
> +		return rc;
> +
> +	debugfs = pmbus_get_debugfs_dir(client);
> +	if (!debugfs)
> +		return rc;
> +
> +	/* ccin is not available, create a symlink from the
> +	 * mfr_serial to ccin as required by hwmon */

There is no such hwmon requirement (hwmon neither knows nor
cares about "ccin"), and this is not a valid multi-line comment.
Please drop this change.

If some userspace code is looking for a debugfs file named "ccin",
change it to read "mfr_serial" instead of "ccin" if "ccin" is
not available. Hacking a kernel driver to meet some arbitrary
userspace requirement is not acceptable.

Thanks,
Guenter

> +	debugfs_create_symlink("ccin", debugfs, "mfr_serial");
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id acbel_fsg032_of_match[] = {
> +	{ .compatible = "acbel,fsg032" },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, acbel_fsg032_of_match);
> +
> +static struct i2c_driver acbel_fsg032_driver = {
> +	.driver = {
> +		.name = "acbel-fsg032",
> +		.of_match_table = acbel_fsg032_of_match,
> +	},
> +	.probe_new = acbel_fsg032_probe,
> +	.id_table = acbel_fsg032_id,
> +};
> +
> +module_i2c_driver(acbel_fsg032_driver);
> +
> +MODULE_AUTHOR("Lakshmi Yadlapati");
> +MODULE_DESCRIPTION("PMBus driver for AcBel Power System power supplies");
> +MODULE_LICENSE("GPL");
> +MODULE_IMPORT_NS(PMBUS);
> -- 
> 2.37.2
>