Re: [PATCH v11 7/7] coco: guest: arm64: Replace dummy CCA device with sysfs ABI

[Catalin Marinas]

On Mon, Sep 14, 2026 at 11:35:11AM +0530, Aneesh Kumar K.V (Arm) wrote:
> diff --git a/Documentation/ABI/testing/sysfs-firmware-cca b/Documentation/ABI/testing/sysfs-firmware-cca
> new file mode 100644
> index 000000000000..bf177d636b92
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-firmware-cca
> @@ -0,0 +1,10 @@
> +What:		/sys/firmware/cca/realm_guest
> +Date:		May 2026
> +Contact:	Linux ARM Kernel Mailing list <linux-arm-kernel@xxxxxxxxxxxxxxxxxxx>
> +Description:	Read-only. Indicates whether the kernel is running as an
> +		Arm Confidential Compute Architecture (CCA) Realm guest.
> +
> +		The value is one of:
> +
> +		0: the kernel is not running as a Realm guest
> +		1: the kernel is running as a Realm guest

Does this file ever read as 0? It is created only if rsi_present and
always reads as 1. That's fine by me but we shouldn't document 0 as a
value. More like if present, it always reads 1 and RSI is present.

> diff --git a/drivers/firmware/arm_rmm/rsi.c b/drivers/firmware/arm_rmm/rsi.c
> index 2dd69febedbd..52f40256bd78 100644
> --- a/drivers/firmware/arm_rmm/rsi.c
> +++ b/drivers/firmware/arm_rmm/rsi.c
> @@ -9,12 +9,15 @@
>  #include <linux/swiotlb.h>
>  #include <linux/platform_device.h>

Nit: I think we can drop this include.

-- 
Catalin