On Tue, 28 Jun 2016 23:37:06 +0200
Heiner Kallweit <hkallwe...@gmail.com> wrote:
> Am 28.06.2016 um 22:09 schrieb Alex Williamson:
> > On Tue, 28 Jun 2016 20:40:37 +0200
> > Heiner Kallweit <hkallwe...@gmail.com> wrote:
> >
> >> The init function ensures that iommu_group_kset can't be NULL.
> >> Therefore this check isn't needed.
> >
> > Have you seen your previous patch? Wasn't this claim that the init
> > function ensures iommu_group_kset more true when iommu_init() called
> > BUG_ON(!iommu_group_kset) than it is when we can get by with just
> > returning -ENOMEM? Thanks,
> >
> Uh, you're right. I was in "module mode" where initcall retvals are
> assessed. Here the initcall retval is ignored.
> If we leave the BUG_ON in however then the check is actually unneeded
> as the system is halted after the BUG_ON.
>
> By the way:
> This check is in iommu_group_get_by_id() and this function doesn't seem
> to have any user in the kernel. It was added about three years ago.
> Is the original intention of this function obsolete meanwhile?
Alexey, this is a question for you. Did the user of this function
never materialize:
commit aa16bea929aed6ea854b55d2be8306a9fb40e694
Author: Alexey Kardashevskiy <a...@ozlabs.ru>
Date: Mon Mar 25 10:23:49 2013 +1100
iommu: Add a function to find an iommu group by id
As IOMMU groups are exposed to the user space by their numbers,
the user space can use them in various kernel APIs so the kernel
might need an API to find a group by its ID.
As an example, QEMU VFIO on PPC64 platform needs it to associate
a logical bus number (LIOBN) with a specific IOMMU group in order
to support in-kernel handling of DMA map/unmap requests.
The patch adds the iommu_group_get_by_id(id) function which performs
such search.
If not, let's remove it. Dead code is broken code. Thanks,
Alex
> >> Signed-off-by: Heiner Kallweit <hkallwe...@gmail.com>
> >> ---
> >> drivers/iommu/iommu.c | 3 ---
> >> 1 file changed, 3 deletions(-)
> >>
> >> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> >> index b36ec9c..b36e24d 100644
> >> --- a/drivers/iommu/iommu.c
> >> +++ b/drivers/iommu/iommu.c
> >> @@ -235,9 +235,6 @@ struct iommu_group *iommu_group_get_by_id(int id)
> >> struct iommu_group *group;
> >> const char *name;
> >>
> >> - if (!iommu_group_kset)
> >> - return NULL;
> >> -
> >> name = kasprintf(GFP_KERNEL, "%d", id);
> >> if (!name)
> >> return NULL;
> >
> >
>
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
