Re: [PATCH V10 4/9] vfio: platform: add support for ACPI probe

[okaya]

On 2016-07-18 20:00, Alex Williamson wrote:
> On Mon, 18 Jul 2016 19:09:22 -0400
> Sinan Kaya <okaya@xxxxxxxxxxxxxx> wrote:
>
> > The code is using the compatible DT string to associate a reset driver
> > with the actual device itself. The compatible string does not exist on
> > ACPI based systems. HID is the unique identifier for a device driver
> > instead.
> >
> > Signed-off-by: Sinan Kaya <okaya@xxxxxxxxxxxxxx>
> > ---
> >  drivers/vfio/platform/vfio_platform_common.c  | 69 
> > +++++++++++++++++++++++++--
> >  drivers/vfio/platform/vfio_platform_private.h |  1 +
> >  2 files changed, 65 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/vfio/platform/vfio_platform_common.c 
> > b/drivers/vfio/platform/vfio_platform_common.c
> > index 6be92c3..a5299f6 100644
> > --- a/drivers/vfio/platform/vfio_platform_common.c
> > +++ b/drivers/vfio/platform/vfio_platform_common.c
> > @@ -13,6 +13,7 @@
> >   */
> >
> >  #include <linux/device.h>
> > +#include <linux/acpi.h>
> >  #include <linux/iommu.h>
> >  #include <linux/module.h>
> >  #include <linux/mutex.h>
> > @@ -49,6 +50,32 @@ static vfio_platform_reset_fn_t 
> > vfio_platform_lookup_reset(const char *compat,
> >  	return reset_fn;
> >  }
> >
> > +static int vfio_platform_acpi_probe(struct vfio_platform_device 
> > *vdev,
> > +				    struct device *dev)
> > +{
> > +	struct acpi_device *adev;
> > +
> > +	if (acpi_disabled)
> > +		return -EPERM;
> > +
> > +	adev = ACPI_COMPANION(dev);
>
> I didn't necessarily have a problem with this being set in the
> declaration.

I think this is better. If ACPI is disabled, it is dangerous to call an 
ACPI API.


> > +	if (!adev) {
> > +		pr_err("VFIO: ACPI companion device not found for %s\n",
> > +			vdev->name);
> > +		return -ENODEV;
> > +	}
> > +
> > +#ifdef CONFIG_ACPI
> > +	vdev->acpihid = acpi_device_hid(adev);
> > +	if (!vdev->acpihid) {
> > +		pr_err("VFIO: cannot find ACPI HID for %s\n",
> > +		       vdev->name);
> > +		return -EINVAL;
> > +	}
> > +#endif
> > +	return WARN_ON(!vdev->acpihid) ? -ENOENT : 0;
>
> ?!?!  The point was that that entire if{} branch is unnecessary.  The
> WARN_ON handles the (impossible) case of !vdev->acpihid.  We just need:
>
> #ifdef CONFIG_ACPI
> 	vdev->acpihid = acpi_device_hid(adev);
> #endif
> 	return WARN_ON(!vdev->acpihid) ? -ENOENT : 0;

OK, got it now. I thought you were trying to get rid of #else

> nit, might make sense to replace EPERM with ENOENT and use EINVAL here.

Sure, will take carr of it.

Anything else I need to take care of?

> > +}
> > +
> >  static bool vfio_platform_has_reset(struct vfio_platform_device 
> > *vdev)
> >  {
> >  	return vdev->of_reset ? true : false;
> > @@ -547,6 +574,37 @@ static const struct vfio_device_ops 
> > vfio_platform_ops = {
> >  	.mmap		= vfio_platform_mmap,
> >  };
> >
> > +int vfio_platform_of_probe(struct vfio_platform_device *vdev,
> > +			   struct device *dev)
> > +{
> > +	int ret;
> > +
> > +	ret = device_property_read_string(dev, "compatible",
> > +					  &vdev->compat);
> > +	if (ret)
> > +		pr_err("VFIO: cannot retrieve compat for %s\n",
> > +			vdev->name);
> > +
> > +	return ret;
> > +}
> > +
> > +/*
> > + * There can be two kernel build combinations. One build where
> > + * ACPI is not selected in Kconfig and another one with the ACPI 
> > Kconfig.
> > + *
> > + * In the first case, vfio_platform_acpi_probe will return since
> > + * acpi_disabled is 1. DT user will not see any kind of messages from
> > + * ACPI.
> > + *
> > + * In the second case, both DT and ACPI is compiled in but the system 
> > is
> > + * booting with any of these combinations.
> > + *
> > + * If the firmware is DT type, then acpi_disabled is 1. The ACPI 
> > probe routine
> > + * terminates immediately without any messages.
> > + *
> > + * If the firmware is ACPI type, then acpi_disabled is 0. All other 
> > checks are
> > + * valid checks. We cannot claim that this system is DT.
> > + */
> >  int vfio_platform_probe_common(struct vfio_platform_device *vdev,
> >  			       struct device *dev)
> >  {
> > @@ -556,11 +614,12 @@ int vfio_platform_probe_common(struct 
> > vfio_platform_device *vdev,
> >  	if (!vdev)
> >  		return -EINVAL;
> >
> > -	ret = device_property_read_string(dev, "compatible", &vdev->compat);
> > -	if (ret) {
> > -		pr_err("VFIO: cannot retrieve compat for %s\n", vdev->name);
> > -		return -EINVAL;
> > -	}
> > +	ret = vfio_platform_acpi_probe(vdev, dev);
> > +	if (ret)
> > +		ret = vfio_platform_of_probe(vdev, dev);
> > +
> > +	if (ret)
> > +		return ret;
> >
> >  	vdev->device = dev;
> >
> > diff --git a/drivers/vfio/platform/vfio_platform_private.h 
> > b/drivers/vfio/platform/vfio_platform_private.h
> > index 71ed7d1..ba9e4f8 100644
> > --- a/drivers/vfio/platform/vfio_platform_private.h
> > +++ b/drivers/vfio/platform/vfio_platform_private.h
> > @@ -58,6 +58,7 @@ struct vfio_platform_device {
> >  	struct mutex			igate;
> >  	struct module			*parent_module;
> >  	const char			*compat;
> > +	const char			*acpihid;
> >  	struct module			*reset_module;
> >  	struct device			*device;