On Mon, Mar 29, 2021 at 05:51:01PM +0300, Andy Shevchenko wrote:

On Mon, Mar 29, 2021 at 4:46 PM Greg Kroah-Hartman
[off-list ref] wrote:

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On Mon, Mar 29, 2021 at 04:01:18PM +0300, Andy Shevchenko wrote:

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On Sun, Mar 28, 2021 at 03:02:24PM +0200, Greg Kroah-Hartman wrote:

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On Sun, Mar 28, 2021 at 03:56:26PM +0300, Andy Shevchenko wrote:

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On Sun, Mar 28, 2021 at 9:47 AM Greg Kroah-Hartman
[off-list ref] wrote:

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On Sun, Mar 28, 2021 at 12:20:07AM +0200, Andy Shevchenko wrote:

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It's very convenient to see what properties and their values
are currently being assigned in the registered software nodes.

...

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+             for (i = 0; i < prop->length / sizeof(u8); i++)
+                     len += sysfs_emit_at(buf, len, "%u,", ((u8 *)pointer)[i]);

No, sysfs is "one value per file", and that is not what you are showing
here at all :(

It is following: it's a "one value" for property in question,

As we may read in [1]: "...so it is socially acceptable to express an
array of values of the same type."

And here is exactly the case: *values of the same type*.

So what is it going to look like exactly?

Basically we have two approaches (already done in the kernel!) use space or
comma for a separator. So:
 - for boolean it will be an empty string (and it's one value always)
 - for integers it will be, for example, '0,1,2' (w/o single quotes)
   for property array with values 0, 1, and 2
 - for plain integers or arrays out of 1 element it will be plain integer
 - for strings it will be, for example, '"str1","str2"' (w/o single quotes)
   for array of string { "str1", "str2" }
 - for single string or array out of 1 element, it will be '"str"' (w/o single
   quotes)

This should be a part of documentation.

And I will complain then too, these "lists of values" are not for sysfs,
sorry.

How can you recommend showing an array(s) of values of the same type?

I do not think that is something that should be shown in sysfs if at all
possible.

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And what tool is going to be
there to parse this mess?  Who is going to to use it?

I guess something like hwinfo (needs a patch).

If nothing needs this, then why are you adding these?

OK, I will prepare tools first, but I have no idea for the format. So,
how can I be sure that tools will accept the patch if there is no
kernel interface available? Seems like a stale case.

Develop both together.  Do not think that you will get the kernel format
right without actually knowing what userspace needs/wants.  That is
crazy.

thanks,

greg k-h