Re: [PATCH] net: lan743x: LAN743X selects FIXED_PHY to resolve a link error

[Simon Horman]

On Sun, Feb 26, 2023 at 07:15:01AM -0800, Tom Rix wrote:
> 
> 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@xxxxxxxxxx>
> > > > > > 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.

FWIIW, I'm happy with a cleanup.
And in that chase there should be no fixes tag
(conversely, if it is a fix, then there should be a fixes tag).

As a cleanup, I suggest targeting this at net-next ([PATCH net-next]).
As net-next is currently closed you'll need to wait for it to
re-open. I expect that will happen next week, after v6.3-rc2 has been tagged.

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

I think updating the patch description by adding something like
"This problem occurs when LAN743X=y and FIXED_PHY=m." would be sufficient.