Re: [PATCH v3 2/3] docs-rst: driver-api: Add infiniband interface documentation

[Jason Gunthorpe]

On Tue, Jan 22, 2019 at 12:00:34PM +0200, Joel Nider wrote:
> A short document regarding the user verbs interface implementation on
> the kernel side. Also, the corresponding index entry in the
> documentation tree.
> 
> Signed-off-by: Joel Nider <joeln@xxxxxxxxxx>
>  Documentation/driver-api/index.rst      |  1 +
>  Documentation/driver-api/infiniband.rst | 73 +++++++++++++++++++++++++++++++++
>  2 files changed, 74 insertions(+)
>  create mode 100644 Documentation/driver-api/infiniband.rst
> 
> diff --git a/Documentation/driver-api/index.rst b/Documentation/driver-api/index.rst
> index ab38ced..ecb3f8a5 100644
> +++ b/Documentation/driver-api/index.rst
> @@ -28,6 +28,7 @@ available subsections can be seen below.
>     regulator
>     iio/index
>     input
> +   infiniband
>     usb/index
>     firewire
>     pci/index
> diff --git a/Documentation/driver-api/infiniband.rst b/Documentation/driver-api/infiniband.rst
> new file mode 100644
> index 0000000..2de47ff
> +++ b/Documentation/driver-api/infiniband.rst
> @@ -0,0 +1,73 @@
> +==========================
> +Infiniband Interface Guide
> +==========================
> +
> +This guide is for people who wish to understand the implementation details of
> +handler functions in the Infiniband subsystem. There are currently two system
> +calls for executing Infiniband commands: write() and ioctl(). Older commands
> +are sent to the kernel via write()s on the device files described in
> +:doc:`../userspace-api/rdma_user_verbs`. New commands must use the ioctl()
> +method. For completeness, both mechanisms are described here.
> +
> +The interface between userspace and kernel is kept in sync by checking the
> +version number. In the kernel, it is defined by IB_USER_VERBS_ABI_VERSION
> +(in include/uapi/rdma/ib_user_verbs.h).
> +
> +Write system call
> +-----------------
> +The entry point to the kernel is the ib_uverbs_write() function, which is
> +invoked as a response to the 'write' system call. The requested function is
> +looked up from an array called uverbs_cmd_table which contains function pointers
> +to the various command handlers.

This array was deleted recently

> +Write Command Handlers
> +~~~~~~~~~~~~~~~~~~~~~~
> +These command handler functions are declared
> +with the IB_VERBS_DECLARE_CMD macro in drivers/infiniband/core/uverbs.h. There
> +are also extended commands, which are kept in a similar manner in the
> +uverbs_ex_cmd_table. The extended commands use 64-bit values in the command
> +header, as opposed to the 32-bit values used in the regular command table.

IB_VERBS_DELCARE_CMD is also deleted

> +Objects trees are declared using the DECLARE_UVERBS_OBJECT_TREE macro. This
> +combines all of the objects.

DECLARE_UVERBS_OBJECT_TREE as well

Jason