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

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Date: Tue, 16 Apr 2024 12:49:11 +0200
From: Alexander Graf <graf@...zon.de>
To: Sudan Landge <sudanl@...zon.com>, <tytso@....edu>, <Jason@...c4.com>,
	<robh+dt@...nel.org>, <krzysztof.kozlowski+dt@...aro.org>,
	<conor+dt@...nel.org>, <sathyanarayanan.kuppuswamy@...ux.intel.com>,
	<thomas.lendacky@....com>, <dan.j.williams@...el.com>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC: <dwmw@...zon.co.uk>, <bchalios@...zon.es>, <xmarcalx@...zon.co.uk>
Subject: Re: [PATCH v4 5/5] virt: vmgenid: add support for devicetree bindings


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@...zon.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@...c4.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,
>   	},
>   };
>   



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