Re: [PATCH v2 2/7] platform: cznic: Add preliminary support for Turris Omnia MCU

[Andy Shevchenko <andy@xxxxxxxxxx>]

On Tue, Sep 19, 2023 at 12:38:10PM +0200, Marek Behún wrote:
> Add a new platform driver that exposes the features provided by the
> microcontroller on the Turris Omnia board.

> This commit adds the basic skeleton for the driver.

Read "Submitting Patches" documentation (find "This patch" in it) and amend
your commit message accordingly.

...

> +Date:		August 2023
> +KernelVersion:	6.6

Wrong and outdated. Use phb-crystall-ball to find the closest possible values
for both parameters here.

Ditto for all others with the same issue.

Note, it likely might be part of v6.7, not earlier.

...

> @@ -11,3 +11,4 @@ obj-$(CONFIG_OLPC_EC)		+= olpc/
>  obj-$(CONFIG_GOLDFISH)		+= goldfish/
>  obj-$(CONFIG_CHROME_PLATFORMS)	+= chrome/
>  obj-$(CONFIG_SURFACE_PLATFORMS)	+= surface/
> +obj-$(CONFIG_CZNIC_PLATFORMS)	+= cznic/

Why not ordered (to some extent) here (as you did in the other file)?

...

> +turris-omnia-mcu-objs		:= turris-omnia-mcu-base.o

objs is for user space tools. Kernel code should use m,y.

...

> +#include <linux/hex.h>
> +#include <linux/module.h>

Missing types.h, sysfs.h, mod_devicetable.h, i2c.h, ...

...

> +static int omnia_get_version_hash(struct omnia_mcu *mcu, bool bootloader,
> +				  u8 *version)
> +{
> +	u8 reply[20];
> +	int ret;
> +
> +	ret = omnia_cmd_read(mcu->client, bootloader ? CMD_GET_FW_VERSION_BOOT :
> +						       CMD_GET_FW_VERSION_APP,
> +			     reply, sizeof(reply));

> +	if (ret < 0)

Can it return positive value? What would be the meaning of it?

> +		return ret;

> +	version[40] = '\0';

How do you know the version has enough space?

> +	bin2hex(version, reply, 20);
> +
> +	return 0;
> +}
> +
> +static ssize_t fw_version_hash_show(struct device *dev, char *buf,
> +				    bool bootloader)
> +{
> +	struct omnia_mcu *mcu = i2c_get_clientdata(to_i2c_client(dev));
> +	u8 version[41];

> +	int err;

In two near functions you already inconsistent in the naming of the return code
variable. Be consistent across all your code, i.e. choose one name and use it
everywhere.

> +	err = omnia_get_version_hash(mcu, bootloader, version);
> +	if (err)
> +		return err;
> +
> +	return sysfs_emit(buf, "%s\n", version);
> +}

...

> +	return sysfs_emit(buf, "%#x\n", mcu->features);

"0" will be printed differently, is this on purpose?

...

> +	int ret = omnia_cmd_read_u8(to_i2c_client(dev), CMD_GET_RESET);
> +
> +	if (ret < 0)
> +		return ret;

Better from maintenance perspective to have

	int ret;

	ret = omnia_cmd_read_u8(to_i2c_client(dev), CMD_GET_RESET);
	if (ret < 0)
		return ret;

...

> +static struct attribute *omnia_mcu_attrs[] = {
> +	&dev_attr_fw_version_hash_application.attr,
> +	&dev_attr_fw_version_hash_bootloader.attr,
> +	&dev_attr_fw_features.attr,
> +	&dev_attr_mcu_type.attr,
> +	&dev_attr_reset_selector.attr,

> +	NULL,

No comma for the terminator line. It will make your code robust at compile time
against some misplaced entries.

> +};

> +

Unneeded blank line.

> +ATTRIBUTE_GROUPS(omnia_mcu);

...

> +	u8 version[41];

This magic sizes should go away. Use predefined constant, or allocate on the
heap, depending on the case(s) you have.

...

> +	int status;

My gosh, it's a _third_ name for the same!

> +	status = omnia_cmd_read_u16(mcu->client, CMD_GET_STATUS_WORD);
> +	if (status < 0)
> +		return status;

...

> +	for (int i = 0; i < ARRAY_SIZE(features); ++i) {

Why signed?
Why pre-increment?

> +		if (!(mcu->features & features[i].mask)) {

Wouldn't be better

		if (mcu->features & features[i].mask)
			continue;

?

> +			omnia_info_missing_feature(dev, features[i].name);
> +			suggest_fw_upgrade = true;
> +		}
> +	}

...

> +		dev_info(dev,
> +			 "Consider upgrading MCU firmware with the omnia-mcutool utility.\n");

You have so-o many dev_info() calls, are you sure you not abusing use of that?

...

> +	if (ret) {
> +		dev_err(dev, "Cannot determine MCU supported features: %d\n",
> +			ret);
> +		return ret;

		return dev_err_probe(...);

> +	}

...

> +	if (!client->irq) {
> +		dev_err(dev, "IRQ resource not found\n");
> +		return -ENODATA;
> +	}

Why you need to allocate memory, go through the initial checks, etc and then
fail? What's wrong with checking this first?

Why -ENODATA?!

...

> +static const struct of_device_id of_omnia_mcu_match[] = {
> +	{ .compatible = "cznic,turris-omnia-mcu", },

Inner comma is not needed.

> +	{},

No comma for the terminator entry.

> +};

...

> +static const struct i2c_device_id omnia_mcu_id[] = {
> +	{ "turris-omnia-mcu", 0 },

', 0' part is redundant.

> +	{ }
> +};

...

> +static struct i2c_driver omnia_mcu_driver = {
> +	.probe		= omnia_mcu_probe,
> +	.id_table	= omnia_mcu_id,
> +	.driver		= {
> +		.name	= "turris-omnia-mcu",
> +		.of_match_table = of_omnia_mcu_match,
> +		.dev_groups = omnia_mcu_groups,
> +	},
> +};

> +

Redundant blank line.

> +module_i2c_driver(omnia_mcu_driver);

...

> +#ifndef __DRIVERS_PLATFORM_CZNIC_TURRIS_OMNIA_MCU_H
> +#define __DRIVERS_PLATFORM_CZNIC_TURRIS_OMNIA_MCU_H

WE_LIKE_VERY_LONG_AND_OVERFLOWED_DEFINITIONS_H!

...

> +#include <asm/byteorder.h>

This usually goes after linux/*.h.

> +#include <linux/i2c.h>

Missing types.h, errno.h, ...

+ blank line?

> +#include <linux/turris-omnia-mcu-interface.h>

...

> +	ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
> +	if (likely(ret == ARRAY_SIZE(msgs)))

Why likely()? Please, justify.

> +		return len;

> +	else if (ret < 0)
> +		return ret;
> +	else
> +		return -EIO;

In both cases the 'else' is redundant. Moreover, the usual pattern is to check
for the errors first.

> +}

...

> +#ifndef __INCLUDE_LINUX_TURRIS_OMNIA_MCU_INTERFACE_H
> +#define __INCLUDE_LINUX_TURRIS_OMNIA_MCU_INTERFACE_H

My gosh!

...

> +#include <linux/bits.h>

> +enum commands_e {

Are you sure the name is unique enough / properly namespaced?
Same Q to all enums.

...

> +	/*CTL_RESERVED		= BIT(2),*/

Missing spaces?
Also, needs a comment why this is commented out.

...

> +	CTL_BOOTLOADER		= BIT(7)

Add trailing comma.

-- 
With Best Regards,
Andy Shevchenko