linux-kernel - Re: [PATCH] net: lan743x: LAN743X selects FIXED

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Date:   Sun, 26 Feb 2023 07:15:01 -0800
From:   Tom Rix <trix@...hat.com>
To:     Simon Horman <simon.horman@...igine.com>,
        Andrew Lunn <andrew@...n.ch>
Cc:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, steen.hegelund@...rochip.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH] net: lan743x: LAN743X selects FIXED_PHY to resolve a link
 error


On 2/21/23 8:20 AM, Simon Horman wrote:
> +Arnd
>
> On Tue, Feb 21, 2023 at 03:29:39AM +0100, Andrew Lunn wrote:
>> On Mon, Feb 20, 2023 at 07:46:13AM +0100, Simon Horman wrote:
>>> On Mon, Feb 20, 2023 at 02:19:34AM +0100, Andrew Lunn wrote:
>>>> On Sun, Feb 19, 2023 at 07:16:07PM +0100, Simon Horman wrote:
>>>>> On Sun, Feb 19, 2023 at 10:03:21AM -0500, Tom Rix wrote:
>>>>>> A rand config causes this link error
>>>>>> drivers/net/ethernet/microchip/lan743x_main.o: In function `lan743x_netdev_open':
>>>>>> drivers/net/ethernet/microchip/lan743x_main.c:1512: undefined reference to `fixed_phy_register'
>>>>>>
>>>>>> lan743x_netdev_open is controlled by LAN743X
>>>>>> fixed_phy_register is controlled by FIXED_PHY
>>>>>>
>>>>>> So LAN743X should also select FIXED_PHY
>>>>>>
>>>>>> Signed-off-by: Tom Rix <trix@...hat.com>
>>>>> Hi Tom,
>>>>>
>>>>> I am a little confused by this.
>>>>>
>>>>> I did manage to cook up a config with LAN743X=m and FIXED_PHY not set.
>>>>> But I do not see a build failure, and I believe that is because
>>>>> when FIXED_PHY is not set then a stub version of fixed_phy_register(),
>>>>> defined as static inline in include/linux/phy_fixed.h, is used.
>>>>>
>>>>> Ref: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/tree/include/linux/phy_fixed.h?h=main&id=675f176b4dcc2b75adbcea7ba0e9a649527f53bd#n42
>>>> I'n guessing, but it could be that LAN743X is built in, and FIXED_PHY
>>>> is a module? What might be needed is
>>>>
>>>> depends on FIXED_PHY || FIXED_PHY=n
>>> Thanks Andrew,
>>>
>>> LAN743X=y and FIXED_PHY=m does indeed produce the problem that Tom
>>> describes. And his patch does appear to resolve the problem.
>> O.K. So the commit message needs updating to describe the actual
>> problem.
> Yes, that would be a good improvement.
>
> Perhaps a fixes tag too?
>
>>> Unfortunately your proposed solution seems to run foul of a complex
>>> dependency situation.
>> I was never any good at Kconfig. Arnd is the expert at solving
>> problems like this.
>>
>> You want either everything built in, or FIXED_PHY built in and LAN743X
>> modular, or both modular.
> I _think_ the patch, which uses select FIXED_PHY for LAN743X,
> achieves that.
>
> I CCed Arnd in case he has any input. Though I think I read
> in an recent email from him that he is out most of this week.

I was out last week as well :)

I considered this a cleanup rather than a fix, I can add that fixes tag.

 From my point of view this is a linking problem, I don't mind 
changing,  what commit message should I use ?

Tom

>