[PATCH v4 5/5] virt: vmgenid: add support for devicetree bindings

[PATCH v4 5/5] virt: vmgenid: add support for devicetree bindings

[Sudan Landge]

Extend the vmgenid platform driver to support devicetree bindings.
With this support, hypervisors can send vmgenid notifications to
the virtual machine without the need to enable ACPI.
The bindings are located at:
Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml

Signed-off-by: Sudan Landge <sudanl@amazon.com>
---
 drivers/virt/vmgenid.c | 53 ++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 51 insertions(+), 2 deletions(-)

diff --git a/drivers/virt/vmgenid.c b/drivers/virt/vmgenid.c
index 3d93e3fb94c4..e1ad74116c0c 100644
--- a/drivers/virt/vmgenid.c
+++ b/drivers/virt/vmgenid.c
@@ -2,12 +2,13 @@
 /*
  * Copyright (C) 2022 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
  *
- * The "Virtual Machine Generation ID" is exposed via ACPI and changes when a
+ * The "Virtual Machine Generation ID" is exposed via ACPI or DT and changes when a
  * virtual machine forks or is cloned. This driver exists for shepherding that
  * information to random.c.
  */
 
 #include <linux/acpi.h>
+#include <linux/interrupt.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
@@ -20,6 +21,7 @@ enum { VMGENID_SIZE = 16 };
 struct vmgenid_state {
 	u8 *next_id;
 	u8 this_id[VMGENID_SIZE];
+	int irq;
 };
 
 static void vmgenid_notify(struct device *device)
@@ -43,6 +45,14 @@ vmgenid_acpi_handler(acpi_handle __always_unused handle,
 	vmgenid_notify(dev);
 }
 
+static __maybe_unused irqreturn_t
+vmgenid_of_irq_handler(int __always_unused irq, void *dev)
+{
+	vmgenid_notify(dev);
+
+	return IRQ_HANDLED;
+}
+
 static int __maybe_unused
 setup_vmgenid_state(struct vmgenid_state *state, u8 *next_id)
 {
@@ -106,6 +116,35 @@ static int vmgenid_add_acpi(struct device __maybe_unused *dev,
 #endif
 }
 
+static int vmgenid_add_of(struct platform_device *pdev,
+			  struct vmgenid_state *state)
+{
+	u8 *virt_addr;
+	int ret = 0;
+
+	virt_addr = (u8 *)devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
+	if (IS_ERR(virt_addr))
+		return PTR_ERR(virt_addr);
+
+	ret = setup_vmgenid_state(state, virt_addr);
+	if (ret)
+		return ret;
+
+	ret = platform_get_irq(pdev, 0);
+	if (ret < 0)
+		return ret;
+
+	state->irq = ret;
+	pdev->dev.driver_data = state;
+
+	ret = devm_request_irq(&pdev->dev, state->irq, vmgenid_of_irq_handler,
+			       IRQF_SHARED, "vmgenid", &pdev->dev);
+	if (ret)
+		pdev->dev.driver_data = NULL;
+
+	return ret;
+}
+
 static int vmgenid_add(struct platform_device *pdev)
 {
 	struct vmgenid_state *state;
@@ -116,7 +155,10 @@ static int vmgenid_add(struct platform_device *pdev)
 	if (!state)
 		return -ENOMEM;
 
-	ret = vmgenid_add_acpi(dev, state);
+	if (dev->of_node)
+		ret = vmgenid_add_of(pdev, state);
+	else
+		ret = vmgenid_add_acpi(dev, state);
 
 	if (ret)
 		devm_kfree(dev, state);
@@ -124,6 +166,12 @@ static int vmgenid_add(struct platform_device *pdev)
 	return ret;
 }
 
+static const struct of_device_id vmgenid_of_ids[] = {
+	{ .compatible = "microsoft,vmgenid", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, vmgenid_of_ids);
+
 static const struct acpi_device_id vmgenid_acpi_ids[] = {
 	{ "VMGENCTR", 0 },
 	{ "VM_GEN_COUNTER", 0 },
@@ -136,6 +184,7 @@ static struct platform_driver vmgenid_plaform_driver = {
 	.driver     = {
 		.name   = "vmgenid",
 		.acpi_match_table = vmgenid_acpi_ids,
+		.of_match_table = vmgenid_of_ids,
 	},
 };
 
-- 
2.34.1

Re: [PATCH v4 5/5] virt: vmgenid: add support for devicetree bindings

[Landge, Sudan]

On 09/04/2024 18:07, Sudan Landge wrote:
> Extend the vmgenid platform driver to support devicetree bindings.
> With this support, hypervisors can send vmgenid notifications to
> the virtual machine without the need to enable ACPI.
> The bindings are located at:
> Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml
> 
> Signed-off-by: Sudan Landge <sudanl@amazon.com>
> ---
>   drivers/virt/vmgenid.c | 53 ++++++++++++++++++++++++++++++++++++++++--
>   1 file changed, 51 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/virt/vmgenid.c b/drivers/virt/vmgenid.c
> index 3d93e3fb94c4..e1ad74116c0c 100644
> --- a/drivers/virt/vmgenid.c
> +++ b/drivers/virt/vmgenid.c
> @@ -2,12 +2,13 @@
>   /*
>    * Copyright (C) 2022 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
>    *
> - * The "Virtual Machine Generation ID" is exposed via ACPI and changes when a
> + * The "Virtual Machine Generation ID" is exposed via ACPI or DT and changes when a
>    * virtual machine forks or is cloned. This driver exists for shepherding that
>    * information to random.c.
>    */
>   
>   #include <linux/acpi.h>
> +#include <linux/interrupt.h>
>   #include <linux/kernel.h>
>   #include <linux/module.h>
>   #include <linux/platform_device.h>
> @@ -20,6 +21,7 @@ enum { VMGENID_SIZE = 16 };
>   struct vmgenid_state {
>   	u8 *next_id;
>   	u8 this_id[VMGENID_SIZE];
> +	int irq;
>   };
>   
>   static void vmgenid_notify(struct device *device)
> @@ -43,6 +45,14 @@ vmgenid_acpi_handler(acpi_handle __always_unused handle,
>   	vmgenid_notify(dev);
>   }
>   
> +static __maybe_unused irqreturn_t
> +vmgenid_of_irq_handler(int __always_unused irq, void *dev)
> +{
> +	vmgenid_notify(dev);
> +
> +	return IRQ_HANDLED;
> +}
> +
>   static int __maybe_unused
>   setup_vmgenid_state(struct vmgenid_state *state, u8 *next_id)
>   {
> @@ -106,6 +116,35 @@ static int vmgenid_add_acpi(struct device __maybe_unused *dev,
>   #endif
>   }
>   
> +static int vmgenid_add_of(struct platform_device *pdev,
> +			  struct vmgenid_state *state)
> +{
> +	u8 *virt_addr;
> +	int ret = 0;
> +
> +	virt_addr = (u8 *)devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
> +	if (IS_ERR(virt_addr))
> +		return PTR_ERR(virt_addr);
> +
> +	ret = setup_vmgenid_state(state, virt_addr);
> +	if (ret)
> +		return ret;
> +
> +	ret = platform_get_irq(pdev, 0);
> +	if (ret < 0)
> +		return ret;
> +
> +	state->irq = ret;
> +	pdev->dev.driver_data = state;
> +
> +	ret = devm_request_irq(&pdev->dev, state->irq, vmgenid_of_irq_handler,
> +			       IRQF_SHARED, "vmgenid", &pdev->dev);
> +	if (ret)
> +		pdev->dev.driver_data = NULL;
> +
> +	return ret;
> +}
> +
>   static int vmgenid_add(struct platform_device *pdev)
>   {
>   	struct vmgenid_state *state;
> @@ -116,7 +155,10 @@ static int vmgenid_add(struct platform_device *pdev)
>   	if (!state)
>   		return -ENOMEM;
>   
> -	ret = vmgenid_add_acpi(dev, state);
> +	if (dev->of_node)
> +		ret = vmgenid_add_of(pdev, state);
> +	else
> +		ret = vmgenid_add_acpi(dev, state);
>   
>   	if (ret)
>   		devm_kfree(dev, state);
> @@ -124,6 +166,12 @@ static int vmgenid_add(struct platform_device *pdev)
>   	return ret;
>   }
>   
> +static const struct of_device_id vmgenid_of_ids[] = {
> +	{ .compatible = "microsoft,vmgenid", },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, vmgenid_of_ids);
> +
>   static const struct acpi_device_id vmgenid_acpi_ids[] = {
>   	{ "VMGENCTR", 0 },
>   	{ "VM_GEN_COUNTER", 0 },
> @@ -136,6 +184,7 @@ static struct platform_driver vmgenid_plaform_driver = {
>   	.driver     = {
>   		.name   = "vmgenid",
>   		.acpi_match_table = vmgenid_acpi_ids,
> +		.of_match_table = vmgenid_of_ids,
>   	},
>   };
>   
Due to a mail server error this last patch of the vmgenid series, 
"[PATCH v4 0/5] virt: vmgenid: Add devicetree bindings support", got 
sent separately. Apologies for this. I will resend the patches to 
correct this issue so, I request reviewers to please ignore this patch.

[PATCH v4 5/5] virt: vmgenid: add support for devicetree bindings

[Sudan Landge]

Extend the vmgenid platform driver to support devicetree bindings.
With this support, hypervisors can send vmgenid notifications to
the virtual machine without the need to enable ACPI.
The bindings are located at:
Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml

Signed-off-by: Sudan Landge <sudanl@amazon.com>
---
 drivers/virt/vmgenid.c | 53 ++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 51 insertions(+), 2 deletions(-)

diff --git a/drivers/virt/vmgenid.c b/drivers/virt/vmgenid.c
index 3d93e3fb94c4..e1ad74116c0c 100644
--- a/drivers/virt/vmgenid.c
+++ b/drivers/virt/vmgenid.c
@@ -2,12 +2,13 @@
 /*
  * Copyright (C) 2022 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
  *
- * The "Virtual Machine Generation ID" is exposed via ACPI and changes when a
+ * The "Virtual Machine Generation ID" is exposed via ACPI or DT and changes when a
  * virtual machine forks or is cloned. This driver exists for shepherding that
  * information to random.c.
  */
 
 #include <linux/acpi.h>
+#include <linux/interrupt.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
@@ -20,6 +21,7 @@ enum { VMGENID_SIZE = 16 };
 struct vmgenid_state {
 	u8 *next_id;
 	u8 this_id[VMGENID_SIZE];
+	int irq;
 };
 
 static void vmgenid_notify(struct device *device)
@@ -43,6 +45,14 @@ vmgenid_acpi_handler(acpi_handle __always_unused handle,
 	vmgenid_notify(dev);
 }
 
+static __maybe_unused irqreturn_t
+vmgenid_of_irq_handler(int __always_unused irq, void *dev)
+{
+	vmgenid_notify(dev);
+
+	return IRQ_HANDLED;
+}
+
 static int __maybe_unused
 setup_vmgenid_state(struct vmgenid_state *state, u8 *next_id)
 {
@@ -106,6 +116,35 @@ static int vmgenid_add_acpi(struct device __maybe_unused *dev,
 #endif
 }
 
+static int vmgenid_add_of(struct platform_device *pdev,
+			  struct vmgenid_state *state)
+{
+	u8 *virt_addr;
+	int ret = 0;
+
+	virt_addr = (u8 *)devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
+	if (IS_ERR(virt_addr))
+		return PTR_ERR(virt_addr);
+
+	ret = setup_vmgenid_state(state, virt_addr);
+	if (ret)
+		return ret;
+
+	ret = platform_get_irq(pdev, 0);
+	if (ret < 0)
+		return ret;
+
+	state->irq = ret;
+	pdev->dev.driver_data = state;
+
+	ret = devm_request_irq(&pdev->dev, state->irq, vmgenid_of_irq_handler,
+			       IRQF_SHARED, "vmgenid", &pdev->dev);
+	if (ret)
+		pdev->dev.driver_data = NULL;
+
+	return ret;
+}
+
 static int vmgenid_add(struct platform_device *pdev)
 {
 	struct vmgenid_state *state;
@@ -116,7 +155,10 @@ static int vmgenid_add(struct platform_device *pdev)
 	if (!state)
 		return -ENOMEM;
 
-	ret = vmgenid_add_acpi(dev, state);
+	if (dev->of_node)
+		ret = vmgenid_add_of(pdev, state);
+	else
+		ret = vmgenid_add_acpi(dev, state);
 
 	if (ret)
 		devm_kfree(dev, state);
@@ -124,6 +166,12 @@ static int vmgenid_add(struct platform_device *pdev)
 	return ret;
 }
 
+static const struct of_device_id vmgenid_of_ids[] = {
+	{ .compatible = "microsoft,vmgenid", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, vmgenid_of_ids);
+
 static const struct acpi_device_id vmgenid_acpi_ids[] = {
 	{ "VMGENCTR", 0 },
 	{ "VM_GEN_COUNTER", 0 },
@@ -136,6 +184,7 @@ static struct platform_driver vmgenid_plaform_driver = {
 	.driver     = {
 		.name   = "vmgenid",
 		.acpi_match_table = vmgenid_acpi_ids,
+		.of_match_table = vmgenid_of_ids,
 	},
 };
 
-- 
2.34.1

Re: [PATCH v4 5/5] virt: vmgenid: add support for devicetree bindings

[Alexander Graf]

On 09.04.24 20:11, Sudan Landge wrote:
> Extend the vmgenid platform driver to support devicetree bindings.
> With this support, hypervisors can send vmgenid notifications to
> the virtual machine without the need to enable ACPI.
> The bindings are located at:
> Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml
>
> Signed-off-by: Sudan Landge <sudanl@amazon.com>
> ---
>   drivers/virt/vmgenid.c | 53 ++++++++++++++++++++++++++++++++++++++++--
>   1 file changed, 51 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/virt/vmgenid.c b/drivers/virt/vmgenid.c
> index 3d93e3fb94c4..e1ad74116c0c 100644
> --- a/drivers/virt/vmgenid.c
> +++ b/drivers/virt/vmgenid.c
> @@ -2,12 +2,13 @@
>   /*
>    * Copyright (C) 2022 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
>    *
> - * The "Virtual Machine Generation ID" is exposed via ACPI and changes when a
> + * The "Virtual Machine Generation ID" is exposed via ACPI or DT and changes when a
>    * virtual machine forks or is cloned. This driver exists for shepherding that
>    * information to random.c.
>    */
>   
>   #include <linux/acpi.h>
> +#include <linux/interrupt.h>
>   #include <linux/kernel.h>
>   #include <linux/module.h>
>   #include <linux/platform_device.h>
> @@ -20,6 +21,7 @@ enum { VMGENID_SIZE = 16 };
>   struct vmgenid_state {
>   	u8 *next_id;
>   	u8 this_id[VMGENID_SIZE];
> +	int irq;
>   };
>   
>   static void vmgenid_notify(struct device *device)
> @@ -43,6 +45,14 @@ vmgenid_acpi_handler(acpi_handle __always_unused handle,
>   	vmgenid_notify(dev);
>   }
>   
> +static __maybe_unused irqreturn_t


Why is this maybe_unused? It seems to be always referenced by 
vmgenid_add_of(), no?


> +vmgenid_of_irq_handler(int __always_unused irq, void *dev)
> +{
> +	vmgenid_notify(dev);
> +
> +	return IRQ_HANDLED;
> +}
> +
>   static int __maybe_unused
>   setup_vmgenid_state(struct vmgenid_state *state, u8 *next_id)
>   {
> @@ -106,6 +116,35 @@ static int vmgenid_add_acpi(struct device __maybe_unused *dev,
>   #endif
>   }
>   
> +static int vmgenid_add_of(struct platform_device *pdev,
> +			  struct vmgenid_state *state)
> +{
> +	u8 *virt_addr;
> +	int ret = 0;
> +
> +	virt_addr = (u8 *)devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
> +	if (IS_ERR(virt_addr))
> +		return PTR_ERR(virt_addr);
> +
> +	ret = setup_vmgenid_state(state, virt_addr);
> +	if (ret)
> +		return ret;
> +
> +	ret = platform_get_irq(pdev, 0);
> +	if (ret < 0)
> +		return ret;


Doesn't this error path need to do something about the ioremap'ed 
resource? Or does devm do that automatically for you?

Alex


> +
> +	state->irq = ret;
> +	pdev->dev.driver_data = state;
> +
> +	ret = devm_request_irq(&pdev->dev, state->irq, vmgenid_of_irq_handler,
> +			       IRQF_SHARED, "vmgenid", &pdev->dev);
> +	if (ret)
> +		pdev->dev.driver_data = NULL;
> +
> +	return ret;
> +}
> +
>   static int vmgenid_add(struct platform_device *pdev)
>   {
>   	struct vmgenid_state *state;
> @@ -116,7 +155,10 @@ static int vmgenid_add(struct platform_device *pdev)
>   	if (!state)
>   		return -ENOMEM;
>   
> -	ret = vmgenid_add_acpi(dev, state);
> +	if (dev->of_node)
> +		ret = vmgenid_add_of(pdev, state);
> +	else
> +		ret = vmgenid_add_acpi(dev, state);
>   
>   	if (ret)
>   		devm_kfree(dev, state);
> @@ -124,6 +166,12 @@ static int vmgenid_add(struct platform_device *pdev)
>   	return ret;
>   }
>   
> +static const struct of_device_id vmgenid_of_ids[] = {
> +	{ .compatible = "microsoft,vmgenid", },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, vmgenid_of_ids);
> +
>   static const struct acpi_device_id vmgenid_acpi_ids[] = {
>   	{ "VMGENCTR", 0 },
>   	{ "VM_GEN_COUNTER", 0 },
> @@ -136,6 +184,7 @@ static struct platform_driver vmgenid_plaform_driver = {
>   	.driver     = {
>   		.name   = "vmgenid",
>   		.acpi_match_table = vmgenid_acpi_ids,
> +		.of_match_table = vmgenid_of_ids,
>   	},
>   };
>   



Amazon Development Center Germany GmbH
Krausenstr. 38
10117 Berlin
Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss
Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B
Sitz: Berlin
Ust-ID: DE 289 237 879

Re: [PATCH v4 5/5] virt: vmgenid: add support for devicetree bindings

[Babis Chalios]

On 16/4/24 12:49, Alexander Graf wrote:
>
> On 09.04.24 20:11, Sudan Landge wrote:
>> Extend the vmgenid platform driver to support devicetree bindings.
>> With this support, hypervisors can send vmgenid notifications to
>> the virtual machine without the need to enable ACPI.
>> The bindings are located at:
>> Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml
>>
>> Signed-off-by: Sudan Landge <sudanl@amazon.com>
>> ---
>>   drivers/virt/vmgenid.c | 53 ++++++++++++++++++++++++++++++++++++++++--
>>   1 file changed, 51 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/virt/vmgenid.c b/drivers/virt/vmgenid.c
>> index 3d93e3fb94c4..e1ad74116c0c 100644
>> --- a/drivers/virt/vmgenid.c
>> +++ b/drivers/virt/vmgenid.c
>> @@ -2,12 +2,13 @@
>>   /*
>>    * Copyright (C) 2022 Jason A. Donenfeld <Jason@zx2c4.com>. All 
>> Rights Reserved.
>>    *
>> - * The "Virtual Machine Generation ID" is exposed via ACPI and 
>> changes when a
>> + * The "Virtual Machine Generation ID" is exposed via ACPI or DT and 
>> changes when a
>>    * virtual machine forks or is cloned. This driver exists for 
>> shepherding that
>>    * information to random.c.
>>    */
>>     #include <linux/acpi.h>
>> +#include <linux/interrupt.h>
>>   #include <linux/kernel.h>
>>   #include <linux/module.h>
>>   #include <linux/platform_device.h>
>> @@ -20,6 +21,7 @@ enum { VMGENID_SIZE = 16 };
>>   struct vmgenid_state {
>>       u8 *next_id;
>>       u8 this_id[VMGENID_SIZE];
>> +    int irq;
>>   };
>>     static void vmgenid_notify(struct device *device)
>> @@ -43,6 +45,14 @@ vmgenid_acpi_handler(acpi_handle __always_unused 
>> handle,
>>       vmgenid_notify(dev);
>>   }
>>   +static __maybe_unused irqreturn_t
>
>
> Why is this maybe_unused? It seems to be always referenced by 
> vmgenid_add_of(), no?

You are right, Alex. I removed the attribute and build the kernel 
without `CONFIG_OF`
without any warnings. I will remove it in the next version.

>
>
>> +vmgenid_of_irq_handler(int __always_unused irq, void *dev)
>> +{
>> +    vmgenid_notify(dev);
>> +
>> +    return IRQ_HANDLED;
>> +}
>> +
>>   static int __maybe_unused
>>   setup_vmgenid_state(struct vmgenid_state *state, u8 *next_id)
>>   {
>> @@ -106,6 +116,35 @@ static int vmgenid_add_acpi(struct device 
>> __maybe_unused *dev,
>>   #endif
>>   }
>>   +static int vmgenid_add_of(struct platform_device *pdev,
>> +              struct vmgenid_state *state)
>> +{
>> +    u8 *virt_addr;
>> +    int ret = 0;
>> +
>> +    virt_addr = (u8 *)devm_platform_get_and_ioremap_resource(pdev, 
>> 0, NULL);
>> +    if (IS_ERR(virt_addr))
>> +        return PTR_ERR(virt_addr);
>> +
>> +    ret = setup_vmgenid_state(state, virt_addr);
>> +    if (ret)
>> +        return ret;
>> +
>> +    ret = platform_get_irq(pdev, 0);
>> +    if (ret < 0)
>> +        return ret;
>
>
> Doesn't this error path need to do something about the ioremap'ed 
> resource? Or does devm do that automatically for you?

devm should be doing this automatically according to this:
https://docs.kernel.org/driver-api/driver-model/devres.html#devres

Also, I took a quick look in other drivers and it looks like the virtio-mmio
probe callback follows the same pattern:
https://elixir.bootlin.com/linux/latest/source/drivers/virtio/virtio_mmio.c#L636

Cheers,
Babis

>
> Alex
>
>
>> +
>> +    state->irq = ret;
>> +    pdev->dev.driver_data = state;
>> +
>> +    ret = devm_request_irq(&pdev->dev, state->irq, 
>> vmgenid_of_irq_handler,
>> +                   IRQF_SHARED, "vmgenid", &pdev->dev);
>> +    if (ret)
>> +        pdev->dev.driver_data = NULL;
>> +
>> +    return ret;
>> +}
>> +
>>   static int vmgenid_add(struct platform_device *pdev)
>>   {
>>       struct vmgenid_state *state;
>> @@ -116,7 +155,10 @@ static int vmgenid_add(struct platform_device 
>> *pdev)
>>       if (!state)
>>           return -ENOMEM;
>>   -    ret = vmgenid_add_acpi(dev, state);
>> +    if (dev->of_node)
>> +        ret = vmgenid_add_of(pdev, state);
>> +    else
>> +        ret = vmgenid_add_acpi(dev, state);
>>         if (ret)
>>           devm_kfree(dev, state);
>> @@ -124,6 +166,12 @@ static int vmgenid_add(struct platform_device 
>> *pdev)
>>       return ret;
>>   }
>>   +static const struct of_device_id vmgenid_of_ids[] = {
>> +    { .compatible = "microsoft,vmgenid", },
>> +    { },
>> +};
>> +MODULE_DEVICE_TABLE(of, vmgenid_of_ids);
>> +
>>   static const struct acpi_device_id vmgenid_acpi_ids[] = {
>>       { "VMGENCTR", 0 },
>>       { "VM_GEN_COUNTER", 0 },
>> @@ -136,6 +184,7 @@ static struct platform_driver 
>> vmgenid_plaform_driver = {
>>       .driver     = {
>>           .name   = "vmgenid",
>>           .acpi_match_table = vmgenid_acpi_ids,
>> +        .of_match_table = vmgenid_of_ids,
>>       },
>>   };