[PATCH] firmware: arm_ffa: Treat missing FF-A feature on a platform as a probe miss

[PATCH] firmware: arm_ffa: Treat missing FF-A feature on a platform as a probe miss

[Sudeep Holla]

When FF-A initialisation is driven from a platform device probe, systems
that do not implement FF-A can return -EOPNOTSUPP from the early transport
or version discovery paths. Driver core treats that as a matched probe
failure and prints:

  |  arm-ffa arm-ffa: probe with driver arm-ffa failed with error -95

That is noisy for a firmware interface that can be absent on otherwise
valid systems. Driver core already treats -ENODEV and -ENXIO as quiet
rejected matches, so translate only the early unsupported discovery cases
to -ENODEV. Keep later setup failures unchanged so real FF-A
initialisation problems are still reported as probe failures.

Reported-by: Nathan Chancellor <nathan@kernel.org>
Closes: https://lore.kernel.org/all/20260523001148.GA1319283@ax162
Signed-off-by: Sudeep Holla <sudeep.holla@kernel.org>
---
 drivers/firmware/arm_ffa/driver.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/arm_ffa/driver.c b/drivers/firmware/arm_ffa/driver.c
index 54984e1b9741..0f468362c288 100644
--- a/drivers/firmware/arm_ffa/driver.c
+++ b/drivers/firmware/arm_ffa/driver.c
@@ -2109,7 +2109,7 @@ static int ffa_probe(struct platform_device *pdev)
 
 	ret = ffa_transport_init(&invoke_ffa_fn);
 	if (ret)
-		return ret;
+		return ret == -EOPNOTSUPP ? -ENODEV : ret;
 
 	drv_info = kzalloc_obj(*drv_info);
 	if (!drv_info)
@@ -2117,8 +2117,11 @@ static int ffa_probe(struct platform_device *pdev)
 	platform_set_drvdata(pdev, drv_info);
 
 	ret = ffa_version_check(&drv_info->version);
-	if (ret)
+	if (ret) {
+		if (ret == -EOPNOTSUPP)
+			ret = -ENODEV;
 		goto free_drv_info;
+	}
 
 	if (ffa_id_get(&drv_info->vm_id)) {
 		pr_err("failed to obtain VM id for self\n");
-- 
2.43.0

Re: [PATCH] firmware: arm_ffa: Treat missing FF-A feature on a platform as a probe miss

[Yeoreum Yun]

LGTM.

Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>

On Tue, May 26, 2026 at 11:36:49AM +0100, Sudeep Holla wrote:
> When FF-A initialisation is driven from a platform device probe, systems
> that do not implement FF-A can return -EOPNOTSUPP from the early transport
> or version discovery paths. Driver core treats that as a matched probe
> failure and prints:
> 
>   |  arm-ffa arm-ffa: probe with driver arm-ffa failed with error -95
> 
> That is noisy for a firmware interface that can be absent on otherwise
> valid systems. Driver core already treats -ENODEV and -ENXIO as quiet
> rejected matches, so translate only the early unsupported discovery cases
> to -ENODEV. Keep later setup failures unchanged so real FF-A
> initialisation problems are still reported as probe failures.
> 
> Reported-by: Nathan Chancellor <nathan@kernel.org>
> Closes: https://lore.kernel.org/all/20260523001148.GA1319283@ax162
> Signed-off-by: Sudeep Holla <sudeep.holla@kernel.org>
> ---
>  drivers/firmware/arm_ffa/driver.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/firmware/arm_ffa/driver.c b/drivers/firmware/arm_ffa/driver.c
> index 54984e1b9741..0f468362c288 100644
> --- a/drivers/firmware/arm_ffa/driver.c
> +++ b/drivers/firmware/arm_ffa/driver.c
> @@ -2109,7 +2109,7 @@ static int ffa_probe(struct platform_device *pdev)
>  
>  	ret = ffa_transport_init(&invoke_ffa_fn);
>  	if (ret)
> -		return ret;
> +		return ret == -EOPNOTSUPP ? -ENODEV : ret;
>  
>  	drv_info = kzalloc_obj(*drv_info);
>  	if (!drv_info)
> @@ -2117,8 +2117,11 @@ static int ffa_probe(struct platform_device *pdev)
>  	platform_set_drvdata(pdev, drv_info);
>  
>  	ret = ffa_version_check(&drv_info->version);
> -	if (ret)
> +	if (ret) {
> +		if (ret == -EOPNOTSUPP)
> +			ret = -ENODEV;
>  		goto free_drv_info;
> +	}
>  
>  	if (ffa_id_get(&drv_info->vm_id)) {
>  		pr_err("failed to obtain VM id for self\n");
> -- 
> 2.43.0
> 

-- 
Sincerely,
Yeoreum Yun

Re: [PATCH] firmware: arm_ffa: Treat missing FF-A feature on a platform as a probe miss

[Nathan Chancellor]

On Tue, May 26, 2026 at 11:36:49AM +0100, Sudeep Holla wrote:
> When FF-A initialisation is driven from a platform device probe, systems
> that do not implement FF-A can return -EOPNOTSUPP from the early transport
> or version discovery paths. Driver core treats that as a matched probe
> failure and prints:
> 
>   |  arm-ffa arm-ffa: probe with driver arm-ffa failed with error -95
> 
> That is noisy for a firmware interface that can be absent on otherwise
> valid systems. Driver core already treats -ENODEV and -ENXIO as quiet
> rejected matches, so translate only the early unsupported discovery cases
> to -ENODEV. Keep later setup failures unchanged so real FF-A
> initialisation problems are still reported as probe failures.
> 
> Reported-by: Nathan Chancellor <nathan@kernel.org>
> Closes: https://lore.kernel.org/all/20260523001148.GA1319283@ax162
> Signed-off-by: Sudeep Holla <sudeep.holla@kernel.org>

Appears to work for me.

Tested-by: Nathan Chancellor <nathan@kernel.org>

> ---
>  drivers/firmware/arm_ffa/driver.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/firmware/arm_ffa/driver.c b/drivers/firmware/arm_ffa/driver.c
> index 54984e1b9741..0f468362c288 100644
> --- a/drivers/firmware/arm_ffa/driver.c
> +++ b/drivers/firmware/arm_ffa/driver.c
> @@ -2109,7 +2109,7 @@ static int ffa_probe(struct platform_device *pdev)
>  
>  	ret = ffa_transport_init(&invoke_ffa_fn);
>  	if (ret)
> -		return ret;
> +		return ret == -EOPNOTSUPP ? -ENODEV : ret;
>  
>  	drv_info = kzalloc_obj(*drv_info);
>  	if (!drv_info)
> @@ -2117,8 +2117,11 @@ static int ffa_probe(struct platform_device *pdev)
>  	platform_set_drvdata(pdev, drv_info);
>  
>  	ret = ffa_version_check(&drv_info->version);
> -	if (ret)
> +	if (ret) {
> +		if (ret == -EOPNOTSUPP)
> +			ret = -ENODEV;
>  		goto free_drv_info;
> +	}
>  
>  	if (ffa_id_get(&drv_info->vm_id)) {
>  		pr_err("failed to obtain VM id for self\n");
> -- 
> 2.43.0
> 

-- 
Cheers,
Nathan

Re: [PATCH] firmware: arm_ffa: Treat missing FF-A feature on a platform as a probe miss

[Sudeep Holla]

On Tue, May 26, 2026 at 12:35:43PM -0700, Nathan Chancellor wrote:
> On Tue, May 26, 2026 at 11:36:49AM +0100, Sudeep Holla wrote:
> > When FF-A initialisation is driven from a platform device probe, systems
> > that do not implement FF-A can return -EOPNOTSUPP from the early transport
> > or version discovery paths. Driver core treats that as a matched probe
> > failure and prints:
> > 
> >   |  arm-ffa arm-ffa: probe with driver arm-ffa failed with error -95
> > 
> > That is noisy for a firmware interface that can be absent on otherwise
> > valid systems. Driver core already treats -ENODEV and -ENXIO as quiet
> > rejected matches, so translate only the early unsupported discovery cases
> > to -ENODEV. Keep later setup failures unchanged so real FF-A
> > initialisation problems are still reported as probe failures.
> > 
> > Reported-by: Nathan Chancellor <nathan@kernel.org>
> > Closes: https://lore.kernel.org/all/20260523001148.GA1319283@ax162
> > Signed-off-by: Sudeep Holla <sudeep.holla@kernel.org>
> 
> Appears to work for me.
> 
> Tested-by: Nathan Chancellor <nathan@kernel.org>
>

Thanks for reporting and testing. Much appreciated!

-- 
Regards,
Sudeep

Re: [PATCH] firmware: arm_ffa: Treat missing FF-A feature on a platform as a probe miss

[Sudeep Holla]

On Tue, 26 May 2026 11:36:49 +0100, Sudeep Holla wrote:
> When FF-A initialisation is driven from a platform device probe, systems
> that do not implement FF-A can return -EOPNOTSUPP from the early transport
> or version discovery paths. Driver core treats that as a matched probe
> failure and prints:
> 
>   |  arm-ffa arm-ffa: probe with driver arm-ffa failed with error -95
> 
> [...]

Applied to sudeep.holla/linux (for-next/ffa/updates), thanks!

[1/1] firmware: arm_ffa: Treat missing FF-A feature on a platform as a probe miss
      https://git.kernel.org/sudeep.holla/c/18706ea68fc4

--
Regards,
Sudeep