Re: [PATCH] xen/iommu: smmu: Rework how the SMMU version is detected

[Julien Grall <julien@xxxxxxx>]

On 24/12/2020 17:00, Andrew Cooper wrote:
> On 24/12/2020 16:49, Julien Grall wrote:
> > From: Julien Grall <jgrall@xxxxxxxxxx>
> >
> > Clang 11 will throw the following error:
> >
> > smmu.c:2284:18: error: cast to smaller integer type 'enum 
> > arm_smmu_arch_version' from 'const void *' [-Werror,-Wvoid-pointer-to-enum-cast]
> >          smmu->version = (enum arm_smmu_arch_version)of_id->data;
> >                          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > The error can be prevented by introduce static variable for each SMMU
> > version and store a pointer for each of them.
> >
> > Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
> You can also fix this by casting through (uintptr_t) instead of (enum
> arm_smmu_arch_version), which wouldn't involve an extra indirection.
I thought about using a different cast, but it feels just papering over 
the issue.
But I don't see what's the problem with the extra indirection... It is 
self-contained and only used during the IOMMU initialization.
> Alternatively, you could modify dt_device_match to union void *data with
> uintptr_t val for when you want to actually pass non-pointer data.
>
> ~Andrew
--
Julien Grall