Re: [RFC PATCH v3 0/3] vfio: platform: return device properties for a platform device

[Eric Auger <eric.auger-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>]

Hi Baptiste, Antonios,

What are the plans wrt this series? I am currently integrating another
QEMU VFIO platform devices where this series could be useful I think
(Feb 2015). Do you intend to follow up and bring it upstream?

Alex, do you see some show-stoppers in this series or do you advise to
simply follow-up?

Thank you in advance

Best Regards

Eric


On 12/19/2014 10:20 PM, Antonios Motakis wrote:
> This RFC's intention is to show what an interface to access device
> properties for the VFIO platform driver can look like. These properties
> can be from the device tree node describing the device, or ACPI properties
> in the future.
> 
> If a device property corresponding to a platform device bound by VFIO PLATFORM
> or VFIO AMBA is available, this patch series will allow the user to query
> for this information. This can be useful for userspace drivers to automatically
> query parameters related to the device.
> 
> Specifically for QEMU, reading the "compatible" property of the device tree
> node could be of use to find out what device is being assigned to the guest and
> handle appropriately a wider range of devices in the future, and to generate an
> appropriate device tree for the guest.
> 
> Older versions of this series where specifically targeted at device tree
> properties. This version has been reworked on top of Rafael J. Wysocki's
> uniform device properties API for device tree and ACPI devices. This will allow
> us to use the API in the future with devices described via ACPI.
> 
> This also means a kernel including the uniform device properties API is needed
> to apply these patches, in additon to the VFIO patches, e.g. branch pm+acpi-3.19-rc1
> from https://git.kernel.org/cgit/linux/kernel/git/rafael/linux-pm.git/
> 
> The API to get the list of available properties and the device tree full_name
> have been removed. These probably don't serve an useful purpose, as the user
> of this API need to know anyway what properties are specific to the device he
> wants to access with VFIO. If we decide to reintroduce the list of properties
> in the future, the generic device properties API in the kernel will have to
> be extended accordingly.
> 
> A kernel with this series and all the dependencies applied can be pulled from
> branch vfio-device-properties-v3 from the repository:
> https://github.com/virtualopensystems/linux-kvm-arm.git
> 
> Changes since v2:
>  - Reworked on top of Rafael J. Wysocki's uniform device properties API for
>    device tree and ACPI
>  - Support for u64 array properties
>  - Removed API to get list of available properties and device tree full_name
> Changes since v1:
>  - Updated for VFIO platform patch series v8:
>    VFIO AMBA devices now supported in addition to VFIO PLATFORM devices
>  - Refactored and cleaned up the code
> 
> Antonios Motakis (3):
>   vfio: platform: add device properties skeleton and user API
>   vfio: platform: access device property as a list of strings
>   vfio: platform: return device properties as arrays of unsigned
>     integers
> 
>  drivers/vfio/platform/Makefile                |   3 +-
>  drivers/vfio/platform/properties.c            | 162 ++++++++++++++++++++++++++
>  drivers/vfio/platform/vfio_platform_common.c  |  35 ++++++
>  drivers/vfio/platform/vfio_platform_private.h |   7 ++
>  include/uapi/linux/vfio.h                     |  26 +++++
>  5 files changed, 232 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/vfio/platform/properties.c
>