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

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Date:   Mon, 2 Dec 2019 03:42:13 +0000
From:   Andy Duan <fugang.duan@....com>
To:     Florian Fainelli <f.fainelli@...il.com>,
        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: Florian Fainelli <f.fainelli@...il.com> Sent: Monday, December 2, 2019 11:18 AM
> On 12/1/2019 7:04 PM, Andy Duan wrote:
> > 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.
> 
> Can you use the device driver model to reflect the link between the MDIO bus
> device, its parent Ethernet controller and the second instance Ethernet
> controller? Be it through the use of device links, or an actual
> dev->parent relationship?

For device dependence, device links maybe the good solution.
Since there instance#1 only depends on instance#0 internal mdio bus,
maybe hive off mdio bus driver from instance@0 is a better solution.

@Florian Fainelli, Thanks for your suggestion.

Andy
> --
> Florian