linux-kernel - Re: [PATCH v2] net: dsa: mv88e6xxx: add write access to debugfs regs file

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Date:	Sun, 12 Jul 2015 21:39:30 -0400 (EDT)
From:	Vivien Didelot <vivien.didelot@...oirfairelinux.com>
To:	David <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>,
	Guenter Roeck <linux@...ck-us.net>, andrew@...n.ch,
	linux-kernel <linux-kernel@...r.kernel.org>,
	kernel <kernel@...oirfairelinux.com>
Subject: Re: [PATCH v2] net: dsa: mv88e6xxx: add write access to debugfs
 regs file

Hi David,

On Jul 11, 2015, at 10:08 PM, David davem@...emloft.net wrote:

> From: Vivien Didelot <vivien.didelot@...oirfairelinux.com>
> Date: Sat, 11 Jul 2015 14:36:12 -0400 (EDT)
> 
>> In the meantime, this is really useful for development. i.e. ensuring a good
>> switchdev/DSA interaction without being able to read and write directly the
>> hardware VLAN table, is a bit a PITA. A dynamic debugfs looked appropriate.
> 
> For "development" you can hack the driver, add tracepoints, or use
> another mechanism anyone hacking the kernel (which by definition
> someone doing "development" is doing) can do.
> 
> I do not buy any of your arguments, and you really miss the grand
> opportunity to export the knobs and values in a way which are going
> to:
> 
> 1) Be useful to users
> 
> 2) Be usable by any similar DSA driver, not just _yours_

I hardly see how this debug interface can be made generic to other DSA drivers,
since the format of hardware tables or some registers seem very specific to the
switch chip.

> So please stop this myopic narrow thinking when you add facilities for
> development or export values.  Think of the big picture and long term,
> not just your personal perceived immediate needs of today.

I understand. So it looks like the only reasonable solution here is to revert
this support for the debugfs interface.

Thanks,
-v
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