[PATCH v1 00/17] tee: Use bus callbacks instead of driver callbacks

[PATCH v1 00/17] tee: Use bus callbacks instead of driver callbacks

[Uwe Kleine-König]

Hello,

the objective of this series is to make tee driver stop using callbacks
in struct device_driver. These were superseded by bus methods in 2006
(commit 594c8281f905 ("[PATCH] Add bus_type probe, remove, shutdown
methods.")) but nobody cared to convert all subsystems accordingly.

Here the tee drivers are converted. The first commit is somewhat
unrelated, but simplifies the conversion (and the drivers). It
introduces driver registration helpers that care about setting the bus
and owner. (The latter is missing in all drivers, so by using these
helpers the drivers become more correct.)

The patches #4 - #17 depend on the first two, so if they should be
applied to their respective subsystem trees these must contain the first
two patches first.

Note that after patch #2 is applied, unconverted drivers provoke a
warning in driver_register(), so it would be good for the user
experience if the whole series goes in during a single merge window. So
I guess an immutable branch containing the frist three patches that can
be merged into the other subsystem trees would be sensible.

After all patches are applied, tee_bus_type can be made private to
drivers/tee as it's not used in other places any more.

Best regards
Uwe

Uwe Kleine-König (17):
  tee: Add some helpers to reduce boilerplate for tee client drivers
  tee: Add probe, remove and shutdown bus callbacks to tee_client_driver
  tee: Adapt documentation to cover recent additions
  hwrng: optee - Make use of module_tee_client_driver()
  hwrng: optee - Make use of tee bus methods
  rtc: optee: Migrate to use tee specific driver registration function
  rtc: optee: Make use of tee bus methods
  efi: stmm: Make use of module_tee_client_driver()
  efi: stmm: Make use of tee bus methods
  firmware: arm_scmi: optee: Make use of module_tee_client_driver()
  firmware: arm_scmi: Make use of tee bus methods
  firmware: tee_bnxt: Make use of module_tee_client_driver()
  firmware: tee_bnxt: Make use of tee bus methods
  KEYS: trusted: Migrate to use tee specific driver registration
    function
  KEYS: trusted: Make use of tee bus methods
  tpm/tpm_ftpm_tee: Make use of tee specific driver registration
  tpm/tpm_ftpm_tee: Make use of tee bus methods

 Documentation/driver-api/tee.rst             | 18 +----
 drivers/char/hw_random/optee-rng.c           | 26 ++----
 drivers/char/tpm/tpm_ftpm_tee.c              | 31 +++++---
 drivers/firmware/arm_scmi/transports/optee.c | 32 +++-----
 drivers/firmware/broadcom/tee_bnxt_fw.c      | 30 ++-----
 drivers/firmware/efi/stmm/tee_stmm_efi.c     | 25 ++----
 drivers/rtc/rtc-optee.c                      | 27 ++-----
 drivers/tee/tee_core.c                       | 84 ++++++++++++++++++++
 include/linux/tee_drv.h                      | 12 +++
 security/keys/trusted-keys/trusted_tee.c     | 17 ++--
 10 files changed, 164 insertions(+), 138 deletions(-)


base-commit: 7d0a66e4bb9081d75c82ec4957c50034cb0ea449
-- 
2.47.3

[PATCH v1 04/17] hwrng: optee - Make use of module_tee_client_driver()

[Uwe Kleine-König]

Reduce boilerplate by using the newly introduced module_tee_client_driver().
That takes care of assigning the driver's bus, so the explicit assigning
in this driver can be dropped.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
---
 drivers/char/hw_random/optee-rng.c | 14 +-------------
 1 file changed, 1 insertion(+), 13 deletions(-)

diff --git a/drivers/char/hw_random/optee-rng.c b/drivers/char/hw_random/optee-rng.c
index 96b5d546d136..6ee748c0cf57 100644
--- a/drivers/char/hw_random/optee-rng.c
+++ b/drivers/char/hw_random/optee-rng.c
@@ -281,24 +281,12 @@ static struct tee_client_driver optee_rng_driver = {
 	.id_table	= optee_rng_id_table,
 	.driver		= {
 		.name		= DRIVER_NAME,
-		.bus		= &tee_bus_type,
 		.probe		= optee_rng_probe,
 		.remove		= optee_rng_remove,
 	},
 };
 
-static int __init optee_rng_mod_init(void)
-{
-	return driver_register(&optee_rng_driver.driver);
-}
-
-static void __exit optee_rng_mod_exit(void)
-{
-	driver_unregister(&optee_rng_driver.driver);
-}
-
-module_init(optee_rng_mod_init);
-module_exit(optee_rng_mod_exit);
+module_tee_client_driver(optee_rng_driver);
 
 MODULE_LICENSE("GPL v2");
 MODULE_AUTHOR("Sumit Garg <sumit.garg@linaro.org>");
-- 
2.47.3

[PATCH v1 05/17] hwrng: optee - Make use of tee bus methods

[Uwe Kleine-König]

The tee bus got dedicated callbacks for probe and remove.
Make use of these. This fixes a runtime warning about the driver needing
to be converted to the bus methods.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
---
 drivers/char/hw_random/optee-rng.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/drivers/char/hw_random/optee-rng.c b/drivers/char/hw_random/optee-rng.c
index 6ee748c0cf57..5a3fa0b38497 100644
--- a/drivers/char/hw_random/optee-rng.c
+++ b/drivers/char/hw_random/optee-rng.c
@@ -211,9 +211,9 @@ static int optee_ctx_match(struct tee_ioctl_version_data *ver, const void *data)
 		return 0;
 }
 
-static int optee_rng_probe(struct device *dev)
+static int optee_rng_probe(struct tee_client_device *rng_device)
 {
-	struct tee_client_device *rng_device = to_tee_client_device(dev);
+	struct device *dev = &rng_device->dev;
 	int ret = 0, err = -ENODEV;
 	struct tee_ioctl_open_session_arg sess_arg;
 
@@ -261,12 +261,10 @@ static int optee_rng_probe(struct device *dev)
 	return err;
 }
 
-static int optee_rng_remove(struct device *dev)
+static void optee_rng_remove(struct tee_client_device *tee_dev)
 {
 	tee_client_close_session(pvt_data.ctx, pvt_data.session_id);
 	tee_client_close_context(pvt_data.ctx);
-
-	return 0;
 }
 
 static const struct tee_client_device_id optee_rng_id_table[] = {
@@ -278,11 +276,11 @@ static const struct tee_client_device_id optee_rng_id_table[] = {
 MODULE_DEVICE_TABLE(tee, optee_rng_id_table);
 
 static struct tee_client_driver optee_rng_driver = {
+	.probe		= optee_rng_probe,
+	.remove		= optee_rng_remove,
 	.id_table	= optee_rng_id_table,
 	.driver		= {
 		.name		= DRIVER_NAME,
-		.probe		= optee_rng_probe,
-		.remove		= optee_rng_remove,
 	},
 };
 
-- 
2.47.3

Re: [PATCH v1 04/17] hwrng: optee - Make use of module_tee_client_driver()

[Sumit Garg]

nit for subject: s/hwrng: optee -/hwrng: optee:/

On Thu, Dec 11, 2025 at 06:14:58PM +0100, Uwe Kleine-König wrote:
> Reduce boilerplate by using the newly introduced module_tee_client_driver().
> That takes care of assigning the driver's bus, so the explicit assigning
> in this driver can be dropped.
> 
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
> ---
>  drivers/char/hw_random/optee-rng.c | 14 +-------------
>  1 file changed, 1 insertion(+), 13 deletions(-)
>

Reviewed-by: Sumit Garg <sumit.garg@oss.qualcomm.com>

-Sumit

> diff --git a/drivers/char/hw_random/optee-rng.c b/drivers/char/hw_random/optee-rng.c
> index 96b5d546d136..6ee748c0cf57 100644
> --- a/drivers/char/hw_random/optee-rng.c
> +++ b/drivers/char/hw_random/optee-rng.c
> @@ -281,24 +281,12 @@ static struct tee_client_driver optee_rng_driver = {
>  	.id_table	= optee_rng_id_table,
>  	.driver		= {
>  		.name		= DRIVER_NAME,
> -		.bus		= &tee_bus_type,
>  		.probe		= optee_rng_probe,
>  		.remove		= optee_rng_remove,
>  	},
>  };
>  
> -static int __init optee_rng_mod_init(void)
> -{
> -	return driver_register(&optee_rng_driver.driver);
> -}
> -
> -static void __exit optee_rng_mod_exit(void)
> -{
> -	driver_unregister(&optee_rng_driver.driver);
> -}
> -
> -module_init(optee_rng_mod_init);
> -module_exit(optee_rng_mod_exit);
> +module_tee_client_driver(optee_rng_driver);
>  
>  MODULE_LICENSE("GPL v2");
>  MODULE_AUTHOR("Sumit Garg <sumit.garg@linaro.org>");
> -- 
> 2.47.3
> 
> 

Re: [PATCH v1 05/17] hwrng: optee - Make use of tee bus methods

[Sumit Garg]

nit for subject: s/hwrng: optee -/hwrng: optee:/

On Thu, Dec 11, 2025 at 06:14:59PM +0100, Uwe Kleine-König wrote:
> The tee bus got dedicated callbacks for probe and remove.
> Make use of these. This fixes a runtime warning about the driver needing
> to be converted to the bus methods.
> 
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
> ---
>  drivers/char/hw_random/optee-rng.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)

Reviewed-by: Sumit Garg <sumit.garg@oss.qualcomm.com>

-Sumit

> 
> diff --git a/drivers/char/hw_random/optee-rng.c b/drivers/char/hw_random/optee-rng.c
> index 6ee748c0cf57..5a3fa0b38497 100644
> --- a/drivers/char/hw_random/optee-rng.c
> +++ b/drivers/char/hw_random/optee-rng.c
> @@ -211,9 +211,9 @@ static int optee_ctx_match(struct tee_ioctl_version_data *ver, const void *data)
>  		return 0;
>  }
>  
> -static int optee_rng_probe(struct device *dev)
> +static int optee_rng_probe(struct tee_client_device *rng_device)
>  {
> -	struct tee_client_device *rng_device = to_tee_client_device(dev);
> +	struct device *dev = &rng_device->dev;
>  	int ret = 0, err = -ENODEV;
>  	struct tee_ioctl_open_session_arg sess_arg;
>  
> @@ -261,12 +261,10 @@ static int optee_rng_probe(struct device *dev)
>  	return err;
>  }
>  
> -static int optee_rng_remove(struct device *dev)
> +static void optee_rng_remove(struct tee_client_device *tee_dev)
>  {
>  	tee_client_close_session(pvt_data.ctx, pvt_data.session_id);
>  	tee_client_close_context(pvt_data.ctx);
> -
> -	return 0;
>  }
>  
>  static const struct tee_client_device_id optee_rng_id_table[] = {
> @@ -278,11 +276,11 @@ static const struct tee_client_device_id optee_rng_id_table[] = {
>  MODULE_DEVICE_TABLE(tee, optee_rng_id_table);
>  
>  static struct tee_client_driver optee_rng_driver = {
> +	.probe		= optee_rng_probe,
> +	.remove		= optee_rng_remove,
>  	.id_table	= optee_rng_id_table,
>  	.driver		= {
>  		.name		= DRIVER_NAME,
> -		.probe		= optee_rng_probe,
> -		.remove		= optee_rng_remove,
>  	},
>  };
>  
> -- 
> 2.47.3
> 

Re: [PATCH v1 00/17] tee: Use bus callbacks instead of driver callbacks

[Sumit Garg]

On Thu, Dec 11, 2025 at 06:14:54PM +0100, Uwe Kleine-König wrote:
> Hello,
> 
> the objective of this series is to make tee driver stop using callbacks
> in struct device_driver. These were superseded by bus methods in 2006
> (commit 594c8281f905 ("[PATCH] Add bus_type probe, remove, shutdown
> methods.")) but nobody cared to convert all subsystems accordingly.
> 
> Here the tee drivers are converted. The first commit is somewhat
> unrelated, but simplifies the conversion (and the drivers). It
> introduces driver registration helpers that care about setting the bus
> and owner. (The latter is missing in all drivers, so by using these
> helpers the drivers become more correct.)
> 
> The patches #4 - #17 depend on the first two, so if they should be
> applied to their respective subsystem trees these must contain the first
> two patches first.

Thanks Uwe for your efforts to clean up the boilerplate code for TEE bus
drivers.

> 
> Note that after patch #2 is applied, unconverted drivers provoke a
> warning in driver_register(), so it would be good for the user
> experience if the whole series goes in during a single merge window.

+1

I suggest the whole series goes via the Jens tree since there shouldn't
be any chances for conflict here.

> So
> I guess an immutable branch containing the frist three patches that can
> be merged into the other subsystem trees would be sensible.
> 
> After all patches are applied, tee_bus_type can be made private to
> drivers/tee as it's not used in other places any more.
> 

Feel free to make the tee_bus_type private as the last patch in the series
such that any followup driver follows this clean approach.

-Sumit

> Best regards
> Uwe
> 
> Uwe Kleine-König (17):
>   tee: Add some helpers to reduce boilerplate for tee client drivers
>   tee: Add probe, remove and shutdown bus callbacks to tee_client_driver
>   tee: Adapt documentation to cover recent additions
>   hwrng: optee - Make use of module_tee_client_driver()
>   hwrng: optee - Make use of tee bus methods
>   rtc: optee: Migrate to use tee specific driver registration function
>   rtc: optee: Make use of tee bus methods
>   efi: stmm: Make use of module_tee_client_driver()
>   efi: stmm: Make use of tee bus methods
>   firmware: arm_scmi: optee: Make use of module_tee_client_driver()
>   firmware: arm_scmi: Make use of tee bus methods
>   firmware: tee_bnxt: Make use of module_tee_client_driver()
>   firmware: tee_bnxt: Make use of tee bus methods
>   KEYS: trusted: Migrate to use tee specific driver registration
>     function
>   KEYS: trusted: Make use of tee bus methods
>   tpm/tpm_ftpm_tee: Make use of tee specific driver registration
>   tpm/tpm_ftpm_tee: Make use of tee bus methods
> 
>  Documentation/driver-api/tee.rst             | 18 +----
>  drivers/char/hw_random/optee-rng.c           | 26 ++----
>  drivers/char/tpm/tpm_ftpm_tee.c              | 31 +++++---
>  drivers/firmware/arm_scmi/transports/optee.c | 32 +++-----
>  drivers/firmware/broadcom/tee_bnxt_fw.c      | 30 ++-----
>  drivers/firmware/efi/stmm/tee_stmm_efi.c     | 25 ++----
>  drivers/rtc/rtc-optee.c                      | 27 ++-----
>  drivers/tee/tee_core.c                       | 84 ++++++++++++++++++++
>  include/linux/tee_drv.h                      | 12 +++
>  security/keys/trusted-keys/trusted_tee.c     | 17 ++--
>  10 files changed, 164 insertions(+), 138 deletions(-)
> 
> 
> base-commit: 7d0a66e4bb9081d75c82ec4957c50034cb0ea449
> -- 
> 2.47.3
> 

Re: [PATCH v1 00/17] tee: Use bus callbacks instead of driver callbacks

[Uwe Kleine-König]

[-- Attachment #1: Type: text/plain, Size: 3035 bytes --]

Hello Sumit,

On Mon, Dec 15, 2025 at 04:54:11PM +0900, Sumit Garg wrote:
> On Thu, Dec 11, 2025 at 06:14:54PM +0100, Uwe Kleine-König wrote:
> > Hello,
> > 
> > the objective of this series is to make tee driver stop using callbacks
> > in struct device_driver. These were superseded by bus methods in 2006
> > (commit 594c8281f905 ("[PATCH] Add bus_type probe, remove, shutdown
> > methods.")) but nobody cared to convert all subsystems accordingly.
> > 
> > Here the tee drivers are converted. The first commit is somewhat
> > unrelated, but simplifies the conversion (and the drivers). It
> > introduces driver registration helpers that care about setting the bus
> > and owner. (The latter is missing in all drivers, so by using these
> > helpers the drivers become more correct.)
> > 
> > The patches #4 - #17 depend on the first two, so if they should be
> > applied to their respective subsystem trees these must contain the first
> > two patches first.
> 
> Thanks Uwe for your efforts to clean up the boilerplate code for TEE bus
> drivers.

Thanks for your feedback. I will prepare a v2 and address your comments
(whitespace issues and wrong callback in the shutdown method).

> > Note that after patch #2 is applied, unconverted drivers provoke a
> > warning in driver_register(), so it would be good for the user
> > experience if the whole series goes in during a single merge window.
> 
> +1
> 
> I suggest the whole series goes via the Jens tree since there shouldn't
> be any chances for conflict here.
> 
> > So
> > I guess an immutable branch containing the frist three patches that can
> > be merged into the other subsystem trees would be sensible.
> > 
> > After all patches are applied, tee_bus_type can be made private to
> > drivers/tee as it's not used in other places any more.
> > 
> 
> Feel free to make the tee_bus_type private as the last patch in the series
> such that any followup driver follows this clean approach.

There is a bit more to do for that than I'm willing to invest. With my
patch series applied `tee_bus_type` is still used in
drivers/tee/optee/device.c and drivers/tee/tee_core.c. Maybe it's
sensible to merge these two files into a single one.

The things I wonder about additionally are:

 - if CONFIG_OPTEE=n and CONFIG_TEE=y|m the tee bus is only used for
   drivers but not devices.

 - optee_register_device() calls device_create_file() on
   &optee_device->dev after device_register(&optee_device->dev).
   (Attention half-knowledge!) I think device_create_file() should not
   be called on an already registered device (or you have to send a
   uevent afterwards). This should probably use type attribute groups.
   (Or the need_supplicant attribute should be dropped as it isn't very
   useful. This would maybe be considered an ABI change however.)

 - Why does optee_probe() in drivers/tee/optee/smc_abi.c unregister all
   optee devices in its error path (optee_unregister_devices())?

Best regards
Uwe

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Re: [PATCH v1 00/17] tee: Use bus callbacks instead of driver callbacks

[Sumit Garg]

Hi Uwe,

On Mon, Dec 15, 2025 at 3:02 PM Uwe Kleine-König
<u.kleine-koenig@baylibre.com> wrote:
>
> Hello Sumit,
>
> On Mon, Dec 15, 2025 at 04:54:11PM +0900, Sumit Garg wrote:
> > On Thu, Dec 11, 2025 at 06:14:54PM +0100, Uwe Kleine-König wrote:
> > > Hello,
> > >
> > > the objective of this series is to make tee driver stop using callbacks
> > > in struct device_driver. These were superseded by bus methods in 2006
> > > (commit 594c8281f905 ("[PATCH] Add bus_type probe, remove, shutdown
> > > methods.")) but nobody cared to convert all subsystems accordingly.
> > >
> > > Here the tee drivers are converted. The first commit is somewhat
> > > unrelated, but simplifies the conversion (and the drivers). It
> > > introduces driver registration helpers that care about setting the bus
> > > and owner. (The latter is missing in all drivers, so by using these
> > > helpers the drivers become more correct.)
> > >
> > > The patches #4 - #17 depend on the first two, so if they should be
> > > applied to their respective subsystem trees these must contain the first
> > > two patches first.
> >
> > Thanks Uwe for your efforts to clean up the boilerplate code for TEE bus
> > drivers.
>
> Thanks for your feedback. I will prepare a v2 and address your comments
> (whitespace issues and wrong callback in the shutdown method).
>
> > > Note that after patch #2 is applied, unconverted drivers provoke a
> > > warning in driver_register(), so it would be good for the user
> > > experience if the whole series goes in during a single merge window.
> >
> > +1
> >
> > I suggest the whole series goes via the Jens tree since there shouldn't
> > be any chances for conflict here.
> >
> > > So
> > > I guess an immutable branch containing the frist three patches that can
> > > be merged into the other subsystem trees would be sensible.
> > >
> > > After all patches are applied, tee_bus_type can be made private to
> > > drivers/tee as it's not used in other places any more.
> > >
> >
> > Feel free to make the tee_bus_type private as the last patch in the series
> > such that any followup driver follows this clean approach.
>
> There is a bit more to do for that than I'm willing to invest. With my
> patch series applied `tee_bus_type` is still used in
> drivers/tee/optee/device.c and drivers/tee/tee_core.c.

Oh I see, I guess we need to come with some helpers around device
register/unregister from TEE subsystem as well. Let's plan that for a
followup patch-set, I don't want this patch-set to be bloated more.

> Maybe it's
> sensible to merge these two files into a single one.

It's not possible as the design for TEE bus is to have TEE
implementation drivers like OP-TEE, AMD-TEE, TS-TEE, QTEE and so on to
register devices on the bus.

>
> The things I wonder about additionally are:
>
>  - if CONFIG_OPTEE=n and CONFIG_TEE=y|m the tee bus is only used for
>    drivers but not devices.

Yeah since the devices are rather added by the TEE implementation driver.

>
>  - optee_register_device() calls device_create_file() on
>    &optee_device->dev after device_register(&optee_device->dev).
>    (Attention half-knowledge!) I think device_create_file() should not
>    be called on an already registered device (or you have to send a
>    uevent afterwards). This should probably use type attribute groups.
>    (Or the need_supplicant attribute should be dropped as it isn't very
>    useful. This would maybe be considered an ABI change however.)

The reasoning for this attribute should be explained by commit:
7269cba53d90 ("tee: optee: Fix supplicant based device enumeration").
In summary it's due to a weird dependency for devices we have with the
user-space daemon: tee-supplicant.

>
>  - Why does optee_probe() in drivers/tee/optee/smc_abi.c unregister all
>    optee devices in its error path (optee_unregister_devices())?

This is mostly to take care of if any device got registered before the
failure occured. Let me know if you have a better way to address that.

-Sumit

Re: [PATCH v1 00/17] tee: Use bus callbacks instead of driver callbacks

[Uwe Kleine-König]

[-- Attachment #1: Type: text/plain, Size: 2840 bytes --]

Hello,

On Tue, Dec 16, 2025 at 01:08:38PM +0530, Sumit Garg wrote:
> On Mon, Dec 15, 2025 at 3:02 PM Uwe Kleine-König
> <u.kleine-koenig@baylibre.com> wrote:
> > On Mon, Dec 15, 2025 at 04:54:11PM +0900, Sumit Garg wrote:
> > > Feel free to make the tee_bus_type private as the last patch in the series
> > > such that any followup driver follows this clean approach.
> >
> > There is a bit more to do for that than I'm willing to invest. With my
> > patch series applied `tee_bus_type` is still used in
> > drivers/tee/optee/device.c and drivers/tee/tee_core.c.
> 
> Oh I see, I guess we need to come with some helpers around device
> register/unregister from TEE subsystem as well. Let's plan that for a
> followup patch-set, I don't want this patch-set to be bloated more.

Don't consider me in for that. But it sounds like a nice addition.

> > Maybe it's
> > sensible to merge these two files into a single one.
> 
> It's not possible as the design for TEE bus is to have TEE
> implementation drivers like OP-TEE, AMD-TEE, TS-TEE, QTEE and so on to
> register devices on the bus.

So only OP-TEE uses the bus for devices and the other *-TEE don't. Also
sounds like something worth to be fixed.

> > The things I wonder about additionally are:
> >
> >  - if CONFIG_OPTEE=n and CONFIG_TEE=y|m the tee bus is only used for
> >    drivers but not devices.
> 
> Yeah since the devices are rather added by the TEE implementation driver.
> 
> >
> >  - optee_register_device() calls device_create_file() on
> >    &optee_device->dev after device_register(&optee_device->dev).
> >    (Attention half-knowledge!) I think device_create_file() should not
> >    be called on an already registered device (or you have to send a
> >    uevent afterwards). This should probably use type attribute groups.
> >    (Or the need_supplicant attribute should be dropped as it isn't very
> >    useful. This would maybe be considered an ABI change however.)
> 
> The reasoning for this attribute should be explained by commit:
> 7269cba53d90 ("tee: optee: Fix supplicant based device enumeration").
> In summary it's due to a weird dependency for devices we have with the
> user-space daemon: tee-supplicant.

From reading that once I don't understand it. (But no need to explain
:-)

Still the file should better be added before device_add() is called.

> >  - Why does optee_probe() in drivers/tee/optee/smc_abi.c unregister all
> >    optee devices in its error path (optee_unregister_devices())?
> 
> This is mostly to take care of if any device got registered before the
> failure occured. Let me know if you have a better way to address that.

Without understanding the tee stuff, I'd say: Don't bother and only undo
the things that probe did before the failure.

Best regards
Uwe

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