linux-kernel - Re: [PATCH] scsi: ufs: core: Fix link error when CONFIG

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Message-ID: <CAHUa44FeKSqRQ68FJneK_NNFNxKHWgynLpd4355GYOuJh=S0vA@mail.gmail.com>
Date: Tue, 2 Dec 2025 14:17:07 +0100
From: Jens Wiklander <jens.wiklander@...aro.org>
To: Bean Huo <beanhuo@...pp.de>
Cc: Bart Van Assche <bvanassche@....org>, "Martin K. Petersen" <martin.petersen@...cle.com>, 
	avri.altman@...disk.com, alim.akhtar@...sung.com, jejb@...ux.ibm.com, 
	can.guo@....qualcomm.com, beanhuo@...ron.com, linux-scsi@...r.kernel.org, 
	linux-kernel@...r.kernel.org, kernel test robot <lkp@...el.com>, 
	Ulf Hansson <ulf.hansson@...aro.org>, Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH] scsi: ufs: core: Fix link error when CONFIG_RPMB=m

[+ Ulf and Arnd in CC]

On Tue, Dec 2, 2025 at 1:17 PM Bean Huo <beanhuo@...pp.de> wrote:
>
> On Tue, 2025-12-02 at 12:41 +0100, Jens Wiklander wrote:
> > Hi,
> >
> > On Tue, Dec 2, 2025 at 10:13 AM Bean Huo <beanhuo@...pp.de> wrote:
> > >
> > > On Mon, 2025-12-01 at 16:53 -0800, Bart Van Assche wrote:
> > > > On 12/1/25 2:42 PM, Bean Huo wrote:
> > > > > On Mon, 2025-12-01 at 12:25 -0500, Martin K. Petersen wrote:
> > > > > > > When CONFIG_SCSI_UFSHCD=y and CONFIG_RPMB=m, the kernel fails to
> > > > > > > link
> > > > > > > with undefined references to ufs_rpmb_probe() and ufs_rpmb_remove():
> > > > > > >
> > > > > > >    ld: drivers/ufs/core/ufshcd.c:8950: undefined reference to
> > > > > > > `ufs_rpmb_probe'
> > > > > > >    ld: drivers/ufs/core/ufshcd.c:10505: undefined reference to
> > > > > > > `ufs_rpmb_remove'
> > > > > > >
> > > > > > > The issue occurs because IS_ENABLED(CONFIG_RPMB) evaluates to true
> > > > > > > when CONFIG_RPMB=m, causing the header to declare the real function
> > > > > > > prototypes.
> > > > > >
> > > > > > This now breaks the modular build for me.
> > > > >
> > > > > I tested both IS_BUILTIN and IS_REACHABLE for the RPMB dependencies both
> > > > > work
> > > > > correctly in my configuration.
> > > > >
> > > > > IS_REACHABLE would provide more flexibility for module configurations,
> > > > > but
> > > > > in
> > > > > practice, I don't have experience with UFS being used as a module.
> > > > >
> > > > > Would you prefer IS_REACHABLE for theoretical flexibility, or is
> > > > > IS_BUILTIN
> > > > > acceptable given the typical UFS built-in configuration?
> > > >
> > > > Hi Martin and Bean,
> > > >
> > > > Unless someone comes up with a better solution, I propose to apply this
> > > > patch before sending a pull request to Linus and look into making RPMB
> > > > tristate again at a later time:
> > > >
> > > > diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> > > > index 9d1de68dee27..e0b7f8fb6ecb 100644
> > > > --- a/drivers/misc/Kconfig
> > > > +++ b/drivers/misc/Kconfig
> > > > @@ -105,7 +105,7 @@ config PHANTOM
> > > >           say N here.
> > > >
> > > >   config RPMB
> > > > -       tristate "RPMB partition interface"
> > > > +       bool "RPMB partition interface"
> > > >         depends on MMC || SCSI_UFSHCD
> > > >         help
> > > >           Unified RPMB unit interface for RPMB capable devices such as
> > > > eMMC
> > > > and
> > > >
> > > > Thanks,
> > > >
> > > > Bart.
> > >
> > > Hi Bart, Martin, (and Jens - adding you to this thread),
> > >
> > > Bart, thanks for the proposed solution to change RPMB from tristate
> > > to bool. This makes sense given our use case that UFS is typically
> > > built-in, and RPMB should follow the same pattern.
> > >
> > >
> > > Hi Jens,
> > >
> > > we wanted to make sure you're aware of this proposed change. The reasoning
> > > is:
> > > 1, avoids module dependency complexity between UFS and RPMB
> > > 2, matches typical usage where both are built-in
> > >
> > > Let me know if there are concerns with making RPMB bool instead of tristate.
> >
> > We use "depends on RPMB || !RPMB" in drivers/tee/optee/Kconfig and
> > drivers/mmc/core/Kconfig to handle this problem. Could the same
> > pattern be used here?
> >
>
> Jens,
>
> The pattern/dependecy used in MMC and OP-TEE doesn't apply UFS due to different
> dependency structures:
>
> MMC: The core MMC config doesn't depend on RPMB. Only MMC_BLOCK (a sub-layer)
> has "depends on RPMB || !RPMB", avoiding the cycle.
>
> OP-TEE: RPMB doesn't depend on OPTEE, so "depends on RPMB || !RPMB" in OPTEE
> creates no cycle.
>
> and for UFS:
>
> UFS: This creates a direct circular dependency:
>
> drivers/misc/Kconfig: RPMB depends on SCSI_UFSHCD
> drivers/ufs/Kconfig: SCSI_UFSHCD depends on RPMB
>
> This is why Bart's suggestion to make RPMB bool instead of tristate may be the
> cleaner solution.
>

What will that mean for OPTEE and MMC? That they can't be modules if
RPMB is enabled? Are we moving the problem somewhere else?

Cheers,
Jens