Re: [PATCH v5 1/2] i2c-tools: Allow passing device file paths

[Wolfram Sang <wsa+renesas@sang-engineering.com>]

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Hi Brigham,

finally! Thanks to a long train travel :)

On Wed, Jul 22, 2026 at 02:52:40AM -0600, Brigham Campbell wrote:
> Make i2c-tools binaries accept a device file path or symlink directly.
> This is useful, for example, for use with stable symlinks generated by
> udev.
> 
> In the case of conflict, the bus parameter is parsed with the following
> precedence in order to maintain backwards compatibility:
> 
> number -> name -> device path
> 
> Suggested-by: Gero Schwäricke <gero.schwaericke@sevenlab.de>
> Signed-off-by: Brigham Campbell <me@brighamcampbell.com>

Yes, I like how this turned out in the end. I think the code is easy to
understand. It seems to work well. It took a little time to find one
corner case in need to be dealt with ;) But it is simple enough...

> +	i2cbus_ul = strtoul(i2cbus_arg, &end, 0);
> +	if (!*end && *i2cbus_arg) {
> +		if (i2cbus_ul > 0xFFFFF) {
> +			fprintf(stderr, "Error: I2C bus out of range!\n");
> +			return -2;

This fails if you use a name/path like "1111111111111". A diff like this
makes it work:

diff --git a/tools/i2cbusses.c b/tools/i2cbusses.c
index 40d863f..47ebffa 100644
--- a/tools/i2cbusses.c
+++ b/tools/i2cbusses.c
@@ -436,12 +436,7 @@ int open_i2c_dev(char *i2cbus_arg, char **filename, size_t size, int quiet)
 	char *end;
 
 	i2cbus_ul = strtoul(i2cbus_arg, &end, 0);
-	if (!*end && *i2cbus_arg) {
-		if (i2cbus_ul > 0xFFFFF) {
-			fprintf(stderr, "Error: I2C bus out of range!\n");
-			return -2;
-		}
-
+	if (!*end && *i2cbus_arg && i2cbus_ul < 0x100000) {
 		return open_i2c_dev_by_nr(i2cbus_ul, *filename, size, quiet);
 	}
 

That should do it, or?

> +	fprintf(stderr, "Error: Couldn't interpret `%s' as a bus number, "
> +		"name, or device file path!\n", i2cbus_arg);
> +

I think this error message does its job very well. In my book, no need
to make it more fine-grained.

The rest (including patch 2) looks also good to me.

Thank you and happy hacking,

   Wolfram


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