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

Alex Williamson
2016-07-19T00:00:49Z

On Mon, 18 Jul 2016 19:09:22 -0400
Sinan Kaya <okaya@codeaurora.org> 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@codeaurora.org>
> ---
> 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.

> + 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;

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

> +}
> +
> 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;
>