linux-kernel - Re: [PATCH V5 5/6] vfio: platform: call

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Date:	Mon, 23 May 2016 17:21:27 +0200
From:	Eric Auger <eric.auger@...aro.org>
To:	Sinan Kaya <okaya@...eaurora.org>, kvm@...r.kernel.org,
	timur@...eaurora.org, cov@...eaurora.org, jcm@...hat.com
Cc:	linux-acpi@...r.kernel.org, agross@...eaurora.org,
	linux-arm-msm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Baptiste Reynal <b.reynal@...tualopensystems.com>,
	Alex Williamson <alex.williamson@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V5 5/6] vfio: platform: call _RST method when using ACPI

Hi Sinan,
On 05/16/2016 04:13 AM, Sinan Kaya wrote:
> The device tree code checks for the presence of a reset driver and calls
> the of_reset function pointer by looking up the reset driver as a module.
> 
> ACPI defines _RST method to perform device level reset. After the _RST
> method is executed, the OS can resume using the device.
> 
> This patch checks the presence of _RST method and calls the _RST
> method when reset is requested.
> 
> Signed-off-by: Sinan Kaya <okaya@...eaurora.org>
> ---
>  drivers/vfio/platform/vfio_platform_common.c | 44 ++++++++++++++++++++++++++++
>  1 file changed, 44 insertions(+)
> 
> diff --git a/drivers/vfio/platform/vfio_platform_common.c b/drivers/vfio/platform/vfio_platform_common.c
> index d859d3b..095d5b7 100644
> --- a/drivers/vfio/platform/vfio_platform_common.c
> +++ b/drivers/vfio/platform/vfio_platform_common.c
> @@ -73,21 +73,59 @@ int vfio_platform_acpi_probe(struct vfio_platform_device *vdev,
>  	}
>  	return 0;
>  }
> +
> +static int vfio_platform_acpi_call_reset(struct vfio_platform_device *vdev)
> +{
> +	struct device *dev = vdev->device;
> +	acpi_handle handle = ACPI_HANDLE(dev);
> +	acpi_status acpi_ret;
> +	unsigned long long val;
> +
> +	acpi_ret = acpi_evaluate_integer(handle, "_RST", NULL, &val);
> +	if (ACPI_FAILURE(acpi_ret))
> +		return -EINVAL;
Can't you return something more explicit here? The error code will be
visible to the userspace. Difficult for him to understand the cause of
the failure in that case.

Eric
> +
> +	return 0;
> +}
> +
> +static bool vfio_platform_acpi_has_reset(struct vfio_platform_device *vdev)
> +{
> +	struct device *dev = vdev->device;
> +	acpi_handle handle = ACPI_HANDLE(dev);
> +
> +	return acpi_has_method(handle, "_RST");
> +}
>  #else
>  int vfio_platform_acpi_probe(struct vfio_platform_device *vdev,
>  			     struct device *dev)
>  {
>  	return -EINVAL;
>  }
> +
> +static int vfio_platform_acpi_call_reset(struct vfio_platform_device *vdev)
> +{
> +	return -EINVAL;
> +}
> +
> +static bool vfio_platform_acpi_has_reset(struct vfio_platform_device *vdev)
> +{
> +	return false;
> +}
>  #endif
>  
>  static bool vfio_platform_has_reset(struct vfio_platform_device *vdev)
>  {
> +	if (vdev->acpihid)
> +		return vfio_platform_acpi_has_reset(vdev);
> +
>  	return vdev->of_reset ? true : false;
>  }
>  
>  static void vfio_platform_get_reset(struct vfio_platform_device *vdev)
>  {
> +	if (vdev->acpihid)
> +		return;
> +
>  	vdev->of_reset = vfio_platform_lookup_reset(vdev->compat,
>  						    &vdev->reset_module);
>  	if (!vdev->of_reset) {
> @@ -99,6 +137,9 @@ static void vfio_platform_get_reset(struct vfio_platform_device *vdev)
>  
>  static void vfio_platform_put_reset(struct vfio_platform_device *vdev)
>  {
> +	if (vdev->acpihid)
> +		return;
> +
>  	if (vdev->of_reset)
>  		module_put(vdev->reset_module);
>  }
> @@ -177,6 +218,9 @@ static int vfio_platform_call_reset(struct vfio_platform_device *vdev)
>  		dev_info(vdev->device, "reset\n");
>  		vdev->of_reset(vdev);
>  		return 0;
> +	} else if (vdev->acpihid) {
> +		dev_info(vdev->device, "reset\n");
> +		return vfio_platform_acpi_call_reset(vdev);
>  	}
>  
>  	dev_warn(vdev->device, "no reset function found!\n");
>