netdev - Re: [PATCH] net: stmmac: Move debugfs init/exit to ->probe()/->remove()

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Message-ID: <3f5ef823-4683-04f8-5f3a-0ccfdb472d6d@synopsys.com>
Date:   Tue, 27 Nov 2018 09:02:51 +0000
From:   Jose Abreu <jose.abreu@...opsys.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Jose Abreu <jose.abreu@...opsys.com>
CC:     "David S. Miller" <davem@...emloft.net>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        <netdev@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] net: stmmac: Move debugfs init/exit to
 ->probe()/->remove()

On 26-11-2018 15:34, Thierry Reding wrote:
> On Fri, Nov 23, 2018 at 12:44:02PM +0000, Jose Abreu wrote:
>> On 23-11-2018 12:21, Thierry Reding wrote:
>>> From: Thierry Reding <treding@...dia.com>
>>>
>>> Setting up and tearing down debugfs is current unbalanced, as seen by
>>> this error during resume from suspend:
>>>
>>>     [  752.134067] dwc-eth-dwmac 2490000.ethernet eth0: ERROR failed to create debugfs directory
>>>     [  752.134347] dwc-eth-dwmac 2490000.ethernet eth0: stmmac_hw_setup: failed debugFS registration
>>>
>>> The imbalance happens because the driver creates the debugfs hierarchy
>>> when the device is opened and tears it down when the device is closed.
>>> There's little gain in that, and it could be argued that it is even
>>> surprising because it's not usually done for other devices. Fix the
>>> imbalance by moving the debugfs creation and teardown to the driver's
>>> ->probe() and ->remove() implementations instead.
>>>
>>> Signed-off-by: Thierry Reding <treding@...dia.com>
>>> ---
>>>
>> Did you test trying to dump "descriptors_status" file when
>> interface is not open ? I think that's the main reason why this
>> is not in probe ...
> Indeed, that seems to cause a hang. Still, it doesn't sound like the
> right things to repeatedly create and remove debugfs files just because
> we can't provide the contents when the device is down.

Agree.

>
> How about we return an empty file or an error code instead when the
> interface is down?

I think an error code would be more suitable (ENODEV/EBUSY ?).
Can you submit v2 ?

Thanks and Best Regards,
Jose Miguel Abreu

>
> Thierry