RE: [PATCH v8 02/11] iommu: Introduce a union to struct iommu_resv_region

[Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>]

> -----Original Message-----
> From: Robin Murphy [mailto:robin.murphy@arm.com]
> Sent: 22 March 2022 18:27
> To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>;
> linux-arm-kernel@lists.infradead.org; linux-acpi@vger.kernel.org;
> iommu@lists.linux-foundation.org
> Cc: Linuxarm <linuxarm@huawei.com>; lorenzo.pieralisi@arm.com;
> joro@8bytes.org; will@kernel.org; wanghuiqiang
> <wanghuiqiang@huawei.com>; Guohanjun (Hanjun Guo)
> <guohanjun@huawei.com>; steven.price@arm.com; Sami.Mujawar@arm.com;
> jon@solid-run.com; eric.auger@redhat.com; yangyicong
> <yangyicong@huawei.com>
> Subject: Re: [PATCH v8 02/11] iommu: Introduce a union to struct
> iommu_resv_region
> 
> On 2022-02-21 15:43, Shameer Kolothum wrote:
> > A union is introduced to struct iommu_resv_region to hold
> > any firmware specific data. This is in preparation to add
> > support for IORT RMR reserve regions and the union now holds
> > the RMR specific information.
> >
> > Signed-off-by: Shameer Kolothum
> <shameerali.kolothum.thodi@huawei.com>
> > ---
> >   include/linux/iommu.h | 9 +++++++++
> >   1 file changed, 9 insertions(+)
> >
> > diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> > index de0c57a567c8..b06952a75f95 100644
> > --- a/include/linux/iommu.h
> > +++ b/include/linux/iommu.h
> > @@ -126,6 +126,11 @@ enum iommu_resv_type {
> >   	IOMMU_RESV_SW_MSI,
> >   };
> >
> > +struct iommu_iort_rmr_data {
> > +	u32 *sids;	/* Stream Ids associated with IORT RMR entry */
> 
> Please make this const.
> 
> Further nit: capitalisation of "IDs" in the comment, otherwise I might
> worry about the possibility of Stream Egos too :P

True :). Will do that.

Thanks,
Shameer 

> 
> > +	u32 num_sids;
> > +};
> > +
> >   /**
> >    * struct iommu_resv_region - descriptor for a reserved memory region
> >    * @list: Linked list pointers
> > @@ -133,6 +138,7 @@ enum iommu_resv_type {
> >    * @length: Length of the region in bytes
> >    * @prot: IOMMU Protection flags (READ/WRITE/...)
> >    * @type: Type of the reserved region
> > + * @fw_data: FW specific reserved region data
> 
> Nit: we've got plenty of room to spell out "Firmware-specific", and it
> never hurts to make documentation as easy to read as possible.
> 
> Thanks,
> Robin.
> 
> >    */
> >   struct iommu_resv_region {
> >   	struct list_head	list;
> > @@ -140,6 +146,9 @@ struct iommu_resv_region {
> >   	size_t			length;
> >   	int			prot;
> >   	enum iommu_resv_type	type;
> > +	union {
> > +		struct iommu_iort_rmr_data rmr;
> > +	} fw_data;
> >   };
> >
> >   /**