On 3/29/22 19:57, David Laight wrote:

From: Michael Walle

quoted

Sent: 29 March 2022 17:07

More and more drivers will check for bad characters in the hwmon name
and all are using the same code snippet. Consolidate that code by adding
a new hwmon_sanitize_name() function.

I'm assuming these 'bad' hwmon names come from userspace?
Like ethernet interface names??

Is silently changing the name of the hwmon entries the right
thing to do at all?

What happens if the user tries to create both "foo_bar" and "foo-bar"?
I'm sure that is going to go horribly wrong somewhere.

It would certainly make sense to have a function to verify the name
is actually valid.
Then bad names can be rejected earlier on.

I'm also intrigued about the list of invalid characters:

+static bool hwmon_is_bad_char(const char ch)
+{
+	switch (ch) {
+	case '-':
+	case '*':
+	case ' ':
+	case '\t':
+	case '\n':
+		return true;
+	default:
+		return false;
+	}
+}

If '\t' and '\n' are invalid why are all the other control characters
allowed?
I'm guessing '*' is disallowed because it is the shell wildcard?
So what about '?'.
Then I'd expect '/' to be invalid - but that isn't checked.
Never mind all the values 0x80 to 0xff - they are probably worse
than whitespace.

OTOH why are any characters invalid at all - except '/'?

The name is supposed to reflect a driver name. Usually driver names
are not defined by userspace but by driver authors. The name is used
by libsensors to distinguish a driver from its instantiation.
libsensors uses wildcards in /etc/sensors3.conf. Duplicate names
are expected; there can be many instances of the same driver in
the system. For example, on the system I am typing this on, I have:

/sys/class/hwmon/hwmon0/name:nvme
/sys/class/hwmon/hwmon1/name:nvme
/sys/class/hwmon/hwmon2/name:nouveau
/sys/class/hwmon/hwmon3/name:nct6797
/sys/class/hwmon/hwmon4/name:jc42
/sys/class/hwmon/hwmon5/name:jc42
/sys/class/hwmon/hwmon6/name:jc42
/sys/class/hwmon/hwmon7/name:jc42
/sys/class/hwmon/hwmon8/name:k10temp

hwmon_is_bad_char() filters out characters which interfere with
libsensor's view of driver instances and the configuration data
in /etc/sensors3.conf. For example, again on my system, the
"sensors" command reports the following jc42 and nvme sensors.

jc42-i2c-0-1a
jc42-i2c-0-18
jc42-i2c-0-1b
jc42-i2c-0-19
nvme-pci-0100
nvme-pci-2500

In /etc/sensors3.conf, there might be entries for "jc42-*" or "nvme-*".
I don't think libsensors cares if a driver is named "this/is/my/driver".
That driver would then, assuming it is an i2c driver, show up
with the sensors command as "this/is/my/driver-i2c-0-25" or similar.
If it is named "this%is%my%driver", it would be something like
"this%is%my%driver-i2c-0-25". And so on. We can not permit "jc-42"
because libsensors would not be able to parse something like
"jc-42-*" or "jc-42-i2c-*".

Taking your example, if driver authors implement two drivers, one
named foo-bar and the other foo_bar, it would be the driver authors'
responsibility to provide valid driver names to the hwmon subsystem,
whatever those names might be. If both end up named "foo_bar" and can
as result not be distinguished from each other by libsensors,
or a user of the "sensors" command, that would be entirely the
responsibility of the driver authors. The only involvement of the
hwmon subsystem - and that is optional - would be to provide means
to the drivers to help them ensure that the names are valid, but
not that they are unique.

If there is ever a driver with a driver name that interferes with
libsensors' ability to distinguish the driver name from interface/port
information, we'll be happy to add the offending character(s)
to hwmon_is_bad_char(). Until then, being picky doesn't really
add any value and appears pointless.

Thanks,
Guenter