From: Sergei Shtylyov <sergei.shtylyov@cogentembedded•com>
To: Andrew Lunn <andrew@lunn•ch>,
Vivien Didelot <vivien.didelot@savoirfairelinux•com>
Cc: "David S. Miller" <davem@davemloft•net>,
f.fainelli@gmail•com, arnd@arndb•de, netdev@vger•kernel.org,
kernel@savoirfairelinux•com
Subject: Re: [PATCH 1/5] phylib: don't return NULL from get_phy_device()
Date: Wed, 27 Apr 2016 23:09:37 +0300 [thread overview]
Message-ID: <57211C81.4000903@cogentembedded.com> (raw)
In-Reply-To: <20160427194932.GF29024@lunn.ch>
Hello.
On 04/27/2016 10:49 PM, Andrew Lunn wrote:
>> Sergei Shtylyov <sergei.shtylyov@cogentembedded•com> writes:
>>
>>> Arnd Bergmann asked that get_phy_device() returns either NULL or the error
>>> value, not both on error. Do as he said, return ERR_PTR(-ENODEV) instead
>>> of NULL when the PHY ID registers read as all ones.
>>>
>>> Suggested-by: Arnd Bergmann <arnd@arndb•de>
>>> Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded•com>
>>>
>>> ---
>>> drivers/net/phy/phy_device.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> Index: net-next/drivers/net/phy/phy_device.c
>>> ===================================================================
>>> --- net-next.orig/drivers/net/phy/phy_device.c
>>> +++ net-next/drivers/net/phy/phy_device.c
>>> @@ -529,7 +529,7 @@ struct phy_device *get_phy_device(struct
>>>
>>> /* If the phy_id is mostly Fs, there is no device there */
>>> if ((phy_id & 0x1fffffff) == 0x1fffffff)
>>> - return NULL;
>>> + return ERR_PTR(-ENODEV);
>>>
>>> return phy_device_create(bus, addr, phy_id, is_c45, &c45_ids);
>>> }
>
> This change is wrong, it needs reverting, or the call sights need
> fixing to expect ENODEV.
So this function had a good reason to return NULL, as it turned out... :-(
> The point is, the device not being there is not an error, with respect
> to the code calling this function.
>
> It gets called by mdiobus_scan()
>
> struct phy_device *mdiobus_scan(struct mii_bus *bus, int addr)
> {
> struct phy_device *phydev;
> int err;
>
> phydev = get_phy_device(bus, addr, false);
> if (IS_ERR(phydev) || phydev == NULL)
> return phydev;
>
> So before, we return NULL, if the device was not there. Now we return
> ERR_PTR(-ENODEV).
>
> This is being called by:
>
> int __mdiobus_register(struct mii_bus *bus, struct module *owner)
> {
> struct mdio_device *mdiodev;
> ...
> for (i = 0; i < PHY_MAX_ADDR; i++) {
> if ((bus->phy_mask & (1 << i)) == 0) {
> struct phy_device *phydev;
>
> phydev = mdiobus_scan(bus, i);
> if (IS_ERR(phydev)) {
> err = PTR_ERR(phydev);
> goto error;
> }
> }
> }
>
> This is treating ERR_PTR(-ENODEV) as a fatal error, where as before
> IS_ERR(NULL) would be false and it would continue scanning other
> addresses on the bus.
Thank you for the detailed analysis! (And shame on me for the lack of it.)
> Please revert this, or fix all the callsites such that ENODEV is not a
> fatal error.
OK, I'll do what DaveM decides.
> Andrew
MBR, Sergei
next prev parent reply other threads:[~2016-04-27 20:09 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-24 17:23 [PATCH 0/5] Don't return NULL from get_phy_device() anymore Sergei Shtylyov
2016-04-24 17:25 ` [PATCH 1/5] phylib: don't return NULL from get_phy_device() Sergei Shtylyov
2016-04-25 19:45 ` Florian Fainelli
[not found] ` <874mamzw5q.fsf@ketchup.mtl.sfl>
2016-04-27 19:49 ` Andrew Lunn
2016-04-27 20:09 ` Sergei Shtylyov [this message]
2016-04-27 20:23 ` David Miller
2016-04-27 22:03 ` Arnd Bergmann
2016-04-27 21:47 ` Florian Fainelli
2016-04-27 22:07 ` Arnd Bergmann
2016-04-27 20:12 ` Sergei Shtylyov
2016-04-27 20:11 ` Florian Fainelli
2016-04-24 17:27 ` [PATCH 2/5] xgene: get_phy_device() doesn't return NULL anymore Sergei Shtylyov
2016-04-25 19:46 ` Florian Fainelli
2016-04-24 17:29 ` [PATCH 3/5] fixed_phy: " Sergei Shtylyov
2016-04-25 19:46 ` Florian Fainelli
2016-04-24 17:30 ` [PATCH 4/5] mdio_bus: " Sergei Shtylyov
2016-04-25 19:46 ` Florian Fainelli
2016-04-24 17:31 ` [PATCH 5/5] of_mdio: " Sergei Shtylyov
2016-04-24 17:37 ` Sergei Shtylyov
2016-04-25 19:47 ` Florian Fainelli
2016-04-26 19:41 ` [PATCH 0/5] Don't return NULL from get_phy_device() anymore David Miller
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