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

okaya
2016-07-19T00:16:50Z

On 2016-07-18 20:00, Alex Williamson wrote:
> 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.

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;
>>