linux-kernel - PCI/AER sysfs files violate the rules of how sysfs works

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Date:   Fri, 21 Jun 2019 09:29:11 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Rajat Jain <rajatja@...gle.com>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: PCI/AER sysfs files violate the rules of how sysfs works

Hi,

When working on some documentation scripts to show the
Documentation/ABI/ files in an automated way, I ran across this "gem" of
a sysfs file: Documentation/ABI/testing/sysfs-bus-pci-devices-aer_stats

In it you describe how the files
/sys/bus/pci/devices/<dev>/aer_dev_correctable and
/sys/bus/pci/devices/<dev>/aer_dev_fatal and
/sys/bus/pci/devices/<dev>/aer_dev_nonfatal
all display a bunch of text on multiple lines.

This violates the "one value per sysfs file" rule, and should never have
been merged as-is :(

Please fix it up to be a lot of individual files if your really need all
of those different values.

Remember, sysfs files should never have to have a parser to read them
other than a simple "what is this single value", and you should NEVER
have fun macros like:

        for (i = 0; i < ARRAY_SIZE(strings_array); i++) {               \
                if (strings_array[i])                                   \
                        str += sprintf(str, "%s %llu\n",                \
                                       strings_array[i], stats[i]);     \
                else if (stats[i])                                      \
                        str += sprintf(str, #stats_array "_bit[%d] %llu\n",\
                                       i, stats[i]);                    \
        }                                                               \
        str += sprintf(str, "TOTAL_%s %llu\n", total_string,            \
                       pdev->aer_stats->total_field);                   \

spit out sysfs information.

Note, I am all for not properly checking the length of the sysfs file
when writing to it, but that is ONLY because you "know" that a single
integer will never overflow anything.  Here you are writing a ton of
different values, with no error checking at all.  So just when I thought
it couldn't be any worse...

Please fix.

thanks,

greg k-h