netdev - RE: [EXT] Re: [PATCH net,stable 1/1] net: fec: match the dev

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Message-ID: <VI1PR0402MB3600232AF1CF9203704DCE83FF430@VI1PR0402MB3600.eurprd04.prod.outlook.com>
Date:   Mon, 2 Dec 2019 03:04:16 +0000
From:   Andy Duan <fugang.duan@....com>
To:     David Miller <davem@...emloft.net>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [EXT] Re: [PATCH net,stable 1/1] net: fec: match the dev_id
 between probe and remove

From: netdev-owner@...r.kernel.org <netdev-owner@...r.kernel.org> Sent: Sunday, December 1, 2019 4:28 AM
> From: Andy Duan <fugang.duan@....com>
> Date: Fri, 29 Nov 2019 06:40:28 +0000
> 
> > Test device bind/unbind on i.MX8QM platform:
> > echo 5b040000.ethernet > /sys/bus/platform/drivers/fec/unbind
> > echo 5b040000.ethernet > /sys/bus/platform/drivers/fec/bind
> >
> > error log:
> > pps pps0: new PPS source ptp0 /sys/bus/platform/drivers/fec/bind
> > fec: probe of 5b040000.ethernet failed with error -2
> >
> > It should decrease the dev_id when device is unbinded. So let the
> > fec_dev_id as global variable and let the count match in
> > .probe() and .remvoe().
> >
> > Reported-by: shivani.patel <shivani.patel@...ansystech.com>
> > Signed-off-by: Fugang Duan <fugang.duan@....com>
> 
> This is not correct.
> 
> Nothing says that there is a direct correlation between the devices added and
> the ones removed, nor the order in which these operations occur relative to
> eachother.
> 
> This dev_id allocation is buggy because you aren't using a proper ID allocation
> scheme such as IDR.
David, you are correct. There still has issue to support bind/unbind feature even if use IDR
to allocate ID because enet instance#1 depend on instance#0 internal MDIO bus for some platforms
and we don't know who is the real instance#0 while binging the device.

Do you have any suggestion to implement the bind/unbind feature with current dependence?
Thanks.

Andy
> 
> I'm not applying this patch, it is incorrect and makes things worse rather than
> better.