linux-kernel - Re: [PATCH] iommu: Always define struct iommu

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Date:   Thu, 27 Oct 2022 11:11:24 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>,
        Joerg Roedel <joro@...tes.org>
Cc:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Prathamesh Shete <pshete@...dia.com>, iommu@...ts.linux.dev,
        linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iommu: Always define struct iommu_fwspec

On Thu, Oct 20, 2022 at 01:32:41PM +0200, Ulf Hansson wrote:
> On Tue, 18 Oct 2022 at 12:51, Thierry Reding <thierry.reding@...il.com> wrote:
> >
> > From: Thierry Reding <treding@...dia.com>
> >
> > In order to fully make use of the !IOMMU_API stub functions, make the
> > struct iommu_fwspec always available so that users of the stubs can keep
> > using the structure's internals without causing compile failures.
> >
> > Signed-off-by: Thierry Reding <treding@...dia.com>
> 
> Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>
> 
> > ---
> > Hi Joerg,
> >
> > this is a rebased patch extracted from an ancient series that never
> > ended up getting applied:
> >
> >         https://lore.kernel.org/all/20191209120005.2254786-3-thierry.reding@gmail.com/
> >
> > You had already acked this particular patch, so maybe you can pick this
> > up. I've seen at least two discussions where this was brought up again,
> > so I figured it'd be worth sending this out again because it can help
> > remove a number of #ifdef blocks throughout the kernel.
> 
> Yes, this would certainly help to improve the code. To me, it looks
> like the current stub functions, like dev_iommu_fwspec_get() for
> example, aren't really useful without $subject patch.
> 
> Note that, I have a pending patch for mmc that would benefit from
> this. To prevent me from delaying that, an easy way forward, assuming
> there are no objections of course, would be to send this for 6.1-rc.

Adding Prathamesh for visibility. Another alternative would be to
prepend this to Prathamesh's series with an Acked-by from Joerg.

Joerg, any preference on how to move forward with this?

Thierry

> 
> >
> >  include/linux/iommu.h | 39 +++++++++++++++++++--------------------
> >  1 file changed, 19 insertions(+), 20 deletions(-)
> >
> > diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> > index a325532aeab5..e3295c45d18f 100644
> > --- a/include/linux/iommu.h
> > +++ b/include/linux/iommu.h
> > @@ -173,6 +173,25 @@ enum iommu_dev_features {
> >
> >  #define IOMMU_PASID_INVALID    (-1U)
> >
> > +/**
> > + * struct iommu_fwspec - per-device IOMMU instance data
> > + * @ops: ops for this device's IOMMU
> > + * @iommu_fwnode: firmware handle for this device's IOMMU
> > + * @flags: IOMMU_FWSPEC_* flags
> > + * @num_ids: number of associated device IDs
> > + * @ids: IDs which this device may present to the IOMMU
> > + */
> > +struct iommu_fwspec {
> > +       const struct iommu_ops  *ops;
> > +       struct fwnode_handle    *iommu_fwnode;
> > +       u32                     flags;
> > +       unsigned int            num_ids;
> > +       u32                     ids[];
> > +};
> > +
> > +/* ATS is supported */
> > +#define IOMMU_FWSPEC_PCI_RC_ATS                        (1 << 0)
> > +
> >  #ifdef CONFIG_IOMMU_API
> >
> >  /**
> > @@ -598,25 +617,6 @@ extern struct iommu_group *generic_device_group(struct device *dev);
> >  /* FSL-MC device grouping function */
> >  struct iommu_group *fsl_mc_device_group(struct device *dev);
> >
> > -/**
> > - * struct iommu_fwspec - per-device IOMMU instance data
> > - * @ops: ops for this device's IOMMU
> > - * @iommu_fwnode: firmware handle for this device's IOMMU
> > - * @flags: IOMMU_FWSPEC_* flags
> > - * @num_ids: number of associated device IDs
> > - * @ids: IDs which this device may present to the IOMMU
> > - */
> > -struct iommu_fwspec {
> > -       const struct iommu_ops  *ops;
> > -       struct fwnode_handle    *iommu_fwnode;
> > -       u32                     flags;
> > -       unsigned int            num_ids;
> > -       u32                     ids[];
> > -};
> > -
> > -/* ATS is supported */
> > -#define IOMMU_FWSPEC_PCI_RC_ATS                        (1 << 0)
> > -
> >  /**
> >   * struct iommu_sva - handle to a device-mm bond
> >   */
> > @@ -680,7 +680,6 @@ bool iommu_group_dma_owner_claimed(struct iommu_group *group);
> >
> >  struct iommu_ops {};
> >  struct iommu_group {};
> > -struct iommu_fwspec {};
> >  struct iommu_device {};
> >  struct iommu_fault_param {};
> >  struct iommu_iotlb_gather {};
> > --
> > 2.37.3
> >
> 
> Kind regards
> Uffe

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