Re: [PATCH v4 1/2] i2c-tools: Allow passing device file paths

["Gero Schwäricke" <gero.schwaericke@sevenlab.de>]

Hi Brigham,

On Mon Jul 6, 2026 at 6:27 AM CEST, Brigham Campbell wrote:
> @@ -446,6 +442,38 @@ int open_i2c_dev(int i2cbus, char *filename, size_t size, int quiet)
>  	return file;
>  }
>  
> +int open_i2c_dev_path(const char *i2cbus_arg, int quiet)
> +{
> +	int file = open(i2cbus_arg, O_RDWR);
> +
> +	if (file < 0 && !quiet) {
> +		fprintf(stderr, "Error: Could not open file "
> +			"`%s': %s\n", i2cbus_arg, strerror(errno));
> +		if (errno == EACCES)
> +			fprintf(stderr, "Run as root?\n");
> +	}
> +
> +	return file;
> +}
> +
> +int open_i2c_dev(char *i2cbus_arg, char **filename, size_t size, int quiet)
> +{
> +	int file, i2cbus;
> +
> +	i2cbus = lookup_i2c_bus(i2cbus_arg);
> +
> +	if (i2cbus < 0) {
> +		*filename = i2cbus_arg;
> +		file = open_i2c_dev_path(i2cbus_arg, quiet);
> +		if (file < 0)
> +			fprintf(stderr, "Failed to open `%s' as a bus name "
> +					"and as a path.\n", i2cbus_arg);
> +		return file;
> +	}
> +
> +	return open_i2c_dev_num(i2cbus, *filename, size, quiet);
> +}

It just occurred to me that the zero-copy pointer shuffling may be
overkill: I think using `char *filename`, instead of `char **filename`,
and copying `i2cbus_arg` in case it is a path reduces complexity at a
reasonably small cost of copying 20 bytes in the worst case. But it's a
matter of oppinion I assume.

Best,
Gero

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