linux-kernel - Re: [RESEND v4 4/6] Documentation: misc-devices: Add Documentation for dw-xdata-pcie driver

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Date:   Sun, 7 Feb 2021 00:31:14 +0100
From:   Krzysztof Wilczyński <kw@...ux.com>
To:     Gustavo Pimentel <Gustavo.Pimentel@...opsys.com>
Cc:     linux-doc@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Derek Kiernan <derek.kiernan@...inx.com>,
        Dragan Cvetic <dragan.cvetic@...inx.com>,
        Arnd Bergmann <arnd@...db.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jonathan Corbet <corbet@....net>
Subject: Re: [RESEND v4 4/6] Documentation: misc-devices: Add Documentation
 for dw-xdata-pcie driver

Hi Gustavo,

[...]
> +The interaction with this driver is done through the module parameter and
> +can be changed in runtime. The driver outputs the requested command state
> +information to /var/log/kern.log or dmesg.

The driver does not seem to offer any parameters (aside of using sysfs
for runtime settings), and it also seem to only print what it's doing
when debug level is enabled - unless I am missing something?

[...]
> +Request to stop any current TLP transfer:
> +- Command:
> +	echo 1 > /sys/kernel/dw-xdata-pcie/stop
[...]

When I do the following:

  # echo 1 > /sys/kernel/dw-xdata-pcie/write
  # echo 1 > /sys/kernel/dw-xdata-pcie/stop
  # cat /sys/kernel/dw-xdata-pcie/write

Would output from cat above simply show "0 MB/s" then?  I wonder how
someone using this new driver could tell whether "write" or "read"
traffic generation has been enabled aside of reading the sysfs files,
would adding "/sys/kernel/dw-xdata-pcie/active" be an overkill here?

What do you think?

Krzysztof