linux-kernel - Re: [PATCH v2 2/3] iio: pressure: bmp280: Allow multiple chips id per family of devices

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Date:   Wed, 23 Aug 2023 19:26:10 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Angel Iglesias <ang.iglesiasg@...il.com>
Cc:     linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>
Subject: Re: [PATCH v2 2/3] iio: pressure: bmp280: Allow multiple chips id
 per family of devices

On Wed, Aug 23, 2023 at 05:58:06PM +0200, Angel Iglesias wrote:
> Improve device detection in certain chip families known to have various
> chip ids.

IDs

...

>  #include <linux/completion.h>
>  #include <linux/pm_runtime.h>
>  #include <linux/random.h>
> +#include <linux/overflow.h>

Please, preserve ordering.

...

>  	struct bmp280_data *data;
>  	struct gpio_desc *gpiod;
>  	unsigned int chip_id;
> -	int ret;
> +	int ret, i;

	unsigned int i;

...

> +	if (i == data->chip_info->num_chip_id) {
> +		size_t nbuf;
> +		char *buf;
> +
> +		// 0x<id>, so four chars per number plus one space + ENDL

> +		if (check_mul_overflow(5, data->chip_info->num_chip_id, &nbuf))
> +			return ret;
> +
> +		buf = kmalloc_array(nbuf, sizeof(char), GFP_KERNEL);

We almost never do a array allocation for byte sizes. Instead of the above you
need to use

		buf = kmalloc_array(data->chip_info->num_chip_id, 5, GFP_KERNEL);

> +		if (!buf)

This check assumes that num_chip_id is never 0, so...

> +			return ret;
> +
> +		for (i = 0; i < data->chip_info->num_chip_id; i++)
> +			snprintf(&buf[i*5], nbuf, "0x%x ", data->chip_info->chip_id[i]);

> +		buf[nbuf-1] = '\0';

...this is redundant assignment. sprintf() guarantees the NUL termination.

> +
> +		dev_err(dev, "bad chip id: expected [ %s ] got 0x%x\n", buf, chip_id);

"...expected one of..."

> +		kfree(buf);
> +		return ret;

Oh, I didn't get that you allocated memory only to print a message...


>  	}

-- 
With Best Regards,
Andy Shevchenko