On 5/3/22 08:45, Rob Herring wrote:
> On Wed, Apr 27, 2022 at 11:45:00AM +0200, Clément Léger wrote:
>> When enabling CONFIG_OF on a platform where of_root is not populated by
>> firmware, we end up without a root node. In order to apply overlays and
>> create subnodes of the root node, we need one. This commit creates an
>> empty root node if not present.
>
> The existing unittest essentially does the same thing for running the
> tests on non-DT systems. It should be modified to use this support
> instead. Maybe that's just removing the unittest code that set of_root.
>
> I expect Frank will have some comments.
My preference would be for unflatten_and_copy_device_tree() to
use a compiled in FDT that only contains a root node, in the
case that no valid device tree is found (in other words,
"if (!initial_boot_params)".
unflatten_and_copy_device_tree() calls unittest_unflatten_overlay_base()
after unflattening the device tree passed into the booting kernel. This
step is needed for a specific portion of the unittests.
I'm still looking at the bigger picture of using overlays for the PCIe
card, so more comments will be coming about that bigger picture.
-Frank
>
>> Co-developed-by: Rob Herring <robh@xxxxxxxxxx>
>> Signed-off-by: Rob Herring <robh@xxxxxxxxxx>
>> Signed-off-by: Clément Léger <clement.leger@xxxxxxxxxxx>
>> ---
>> drivers/of/base.c | 16 ++++++++++++++--
>> 1 file changed, 14 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/of/base.c b/drivers/of/base.c
>> index e7d92b67cb8a..6b8584c39f73 100644
>> --- a/drivers/of/base.c
>> +++ b/drivers/of/base.c
>> @@ -177,6 +177,19 @@ void __init of_core_init(void)
>> pr_err("failed to register existing nodes\n");
>> return;
>> }
>> +
>> + if (!of_root) {
>> + of_root = kzalloc(sizeof(*of_root), GFP_KERNEL);
>> + if (!of_root) {
>> + mutex_unlock(&of_mutex);
>> + pr_err("failed to create root node\n");
>> + return;
>> + }
>> +
>> + of_root->full_name = "/";
>> + of_node_init(of_root);
>> + }
>> +
>> for_each_of_allnodes(np) {
>> __of_attach_node_sysfs(np);
>> if (np->phandle && !phandle_cache[of_phandle_cache_hash(np->phandle)])
>> @@ -185,8 +198,7 @@ void __init of_core_init(void)
>> mutex_unlock(&of_mutex);
>>
>> /* Symlink in /proc as required by userspace ABI */
>> - if (of_root)
>> - proc_symlink("device-tree", NULL, "/sys/firmware/devicetree/base");
>> + proc_symlink("device-tree", NULL, "/sys/firmware/devicetree/base");
>> }
>>
>> static struct property *__of_find_property(const struct device_node *np,
>> --
>> 2.34.1
>>
>>
