[Skiboot] [PATCH v10 04/17] core/fdt: OPAL API opal_get_device_tree()

Stewart Smith stewart at linux.vnet.ibm.com
Wed May 11 11:42:01 AEST 2016

Gavin Shan <gwshan at linux.vnet.ibm.com> writes:
> This implements OPAL API opal_get_device_tree(), which will be used
> to retrieve the device sub-tree introduced by newly hot plugged PCI
> devices.
> The argument @phandle of the API indicates the specified device
> node that is the PCI slot's device node in PCI hotplug case. @buf
> is the memory buffer allocated from kernel to hold the FDT blob.
> @len is the length of the memory buffer. The FDT blob is put into
> the memory buffer indicated by @buf and OPAL_SUCCESS is returned
> on success. Otherwise, errcode is returned accordingly.
> Signed-off-by: Gavin Shan <gwshan at linux.vnet.ibm.com>
> ---
>  core/fdt.c         | 111 +++++++++++++++++++++++++++++++++++------------------
>  include/opal-api.h |   3 +-
>  2 files changed, 75 insertions(+), 39 deletions(-)

Also need to add doc/opal-api/opal-get-device-tree-118.txt.

Here's the start of it:

diff --git a/doc/opal-api/opal-get-device-tree-118.txt b/doc/opal-api/opal-get-device-tree-118.txt
new file mode 100644
index 000000000000..17fec7461a8d
--- /dev/null
+++ b/doc/opal-api/opal-get-device-tree-118.txt
@@ -0,0 +1,24 @@
+Get part of the current device tree.
+	uint32_t phandle: phandle of the subtree to get
+	uint64_t buf: buffer for flattended device tree
+	uint64_t len: length of buffer
+The typical use for OPAL_GET_DEVICE_TREE is after the host has been notified
+of a change to hardware at runtime.
+Return Codes:
+- Successfully wrote flattened device tree into buf
+- buf, len or phandle is invalid
+- not enough room in buffer for device tree.
+- nothing to flatten

> diff --git a/core/fdt.c b/core/fdt.c
> index a9392b1..f82927a 100644
> --- a/core/fdt.c
> +++ b/core/fdt.c
> -		fdt_create(fdt, len);
> +static int64_t opal_get_device_tree(uint32_t phandle,
> +				    uint64_t buf,
> +				    uint64_t len)

Another thought on API - have len be a pointer, and in the event of
OPAL_NO_MEM, have it set to a value that will work for this phandle
(assuming nothing more changes in the meantime) - and have that work if
buf is NULL and len=0.

Except that the fdt code fights us against that a bit... but it should
be possible to fix it up to do a decent calculation.

Stewart Smith
OPAL Architect, IBM.

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