Re: [PATCH v2 07/10] arm: make it possible to disable the SMMU driver

[Julien Grall <julien.grall@arm.com>]

Hi,

On 05/22/2018 01:53 AM, Stefano Stabellini wrote:
> Introduce a Kconfig option for the ARM SMMUv1 and SMMUv2 driver.
> 
> Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>
> CC: jbeulich@suse.com
> 
> ---
> Changes in v2:
> - rename HAS_SMMUv2 to SMMUv2
> - move SMMUv2 to xen/drivers/passthrough/Kconfig
> ---
>   xen/drivers/passthrough/Kconfig      | 8 ++++++++
>   xen/drivers/passthrough/arm/Makefile | 2 +-
>   2 files changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/drivers/passthrough/Kconfig b/xen/drivers/passthrough/Kconfig
> index 8d90b67..9bdce65 100644
> --- a/xen/drivers/passthrough/Kconfig
> +++ b/xen/drivers/passthrough/Kconfig
> @@ -1,3 +1,11 @@
>   
>   config HAS_PASSTHROUGH
>   	bool
> +
> +config SMMUv2

It would make sense to have ARM in the name because there are other 
using SMMU in their device name (see Tegra). Furthermore this is not 
only v2 specific.

A better name would be ARM_SMMU.

> +	bool "ARM SMMUv1 and v2 driver"
> +	default y
> +	depends on ARM
> +	---help---
> +	  Driver for the ARM SMMU version 1 and 2, a popular IOMMU by
> +	  ARM.

The driver enables support for any IOMMU based on the ARM System MMU 
architecture versions 1 and 2. ARM provides implementation (SMMU-400, 
SMMU-401, SMMU-500 & co) but there are other existing in the wild (e.g 
Cavium one).

Also, in general it would be useful to state why someone would want to 
enable a driver. So I would rework this message as:

"Support for implementations of the ARM System MMU architecture versions 
1 and 2.

Say Y here if your SoC includes an IOMMU device implementing the ARM 
SMMU architecture".

Cheers,

-- 
Julien Grall

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