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

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Date:   Tue, 9 Feb 2021 00:11:48 +0100
From:   Krzysztof Wilczyński <kw@...ux.com>
To:     Gustavo Pimentel <Gustavo.Pimentel@...opsys.com>
Cc:     "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...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,

[...]
> > 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?
> 
> Yes, it would display 0 MB/s. This driver is to be used mainly by the 
> Synopsys DesignWare HW prototyping team. I don't think the general public 
> will be interested or can use this driver, because requires a special HW 
> block available only for this prototype.

Got it.

> I tried to reduce to the minimal the interfaces, to avoid possible 
> confusion. For instance, even the /sys/kernel/dw-xdata-pcie/stop 
> interface could be avoided, because on the driver unloading or changing 
> the between write or read it calls the stop procedure.

Oh, OK.
 
> Due to the nature of the HW block, it only can allow the write or the 
> read at some given moment, therefore based on the last command enable 
> write or read, we know which mode is this driving working.
> This driver will be used by the testing team on their automation scripts, 
> thus they will know exactly the sequence input.
> 
> Anyway, thanks for your feedback.

Thank you for taking the time to add more details for me.  Much
appreciated.

Krzysztof