linux-kernel - Re: [PATCH 3/4] syscon: Wire up has-inaccessible-regs

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Message-ID: <58ccca49-f30c-4461-b4aa-4985f72c89fb@kernel.org>
Date: Sat, 29 Nov 2025 16:25:28 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Richard Weinberger <richard@....at>, linux-kernel@...r.kernel.org
Cc: linux-omap@...r.kernel.org, devicetree@...r.kernel.org, arnd@...db.de,
 lee@...nel.org, dakr@...nel.org, rafael@...nel.org,
 gregkh@...uxfoundation.org, broonie@...nel.org, tony@...mide.com,
 rogerq@...nel.org, khilman@...libre.com, andreas@...nade.info,
 aaro.koskinen@....fi, conor+dt@...nel.org, krzk+dt@...nel.org,
 robh@...nel.org
Subject: Re: [PATCH 3/4] syscon: Wire up has-inaccessible-regs

On 29/11/2025 15:20, Richard Weinberger wrote:
> Evaluate the has-inaccessible-regs device tree property to disable
> debugfs access if a register map contains dangerous/harmful registers.
> 
> Signed-off-by: Richard Weinberger <richard@....at>
> ---
>  drivers/mfd/syscon.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
> index ae71a2710bed8..73fff0df3f42f 100644
> --- a/drivers/mfd/syscon.c
> +++ b/drivers/mfd/syscon.c
> @@ -70,6 +70,16 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_res)
>  	else if (of_property_read_bool(np, "native-endian"))
>  		syscon_config.val_format_endian = REGMAP_ENDIAN_NATIVE;
>  
> +
> +	/*
> +	 * Disable debugfs access if a register map has various inaccessible
> +	 * registers.
> +	 * In such a case the device driver has to know exactly how and when
> +	 * access is allowed but general access via userspace can cause harm.
> +	 */
> +	if (of_property_read_bool(np, "has-inaccessible-regs"))
> +		syscon_config.debugfs_disable = true;

So you mark ENTIRE device like that? Then you don't need the property.
Your compatible already tells you that (IOW, this is fully deducible
from the compatible).

Best regards,
Krzysztof