On Wed, 5 Jun 2024 19:11:04 +0200
Markus Elfring <Markus.Elfring@xxxxxx> wrote:
> From: Markus Elfring <elfring@xxxxxxxxxxxxxxxxxxxxx>
> Date: Wed, 5 Jun 2024 18:56:19 +0200
>
> Scope-based resource management became supported also for another
> programming interface by contributions of Jonathan Cameron on 2024-02-17.
> See also the commit 59ed5e2d505bf5f9b4af64d0021cd0c96aec1f7c ("device
> property: Add cleanup.h based fwnode_handle_put() scope based cleanup.").
>
> * Thus use the attribute “__free(fwnode_handle)”.
>
> * Reduce the scope for the local variable “fwnode”.
>
> Fixes: fe6d8a9c8e64 ("usb: typec: anx7411: Add Analogix PD ANX7411 support")
> Signed-off-by: Markus Elfring <elfring@xxxxxxxxxxxxxxxxxxxxx>
Hi Markus,
Good catch. However in this case I think this is insufficient.
Also your patch description should more clearly state the bug rather
and impacts (a potential resource leak).
I'm not 100% sure how this should work though.
If the expectation is that a reference to the fwnode is held when we
enter typec_register_port(), then if that errors out then we
need fwnode_handle_put().
If expectation is that the reference is not held, then we should
always call fwnode_handle_put() before that is called.
Internally it just uses this to fill in port->dev.fwnode.
Given typec_get_fw_cap() is called from there and doesn't get a reference
I think expectation is that the fwnode is held by the driver calling
typec_register_port() until that is unregistered.
Hence should be put in the error path of that call in the calling driver.
ctx->typec.port = typec_register_port(dev, cap);
if (IS_ERR(ctx->typec.port)) {
// fwnode_handle_put() in here.
ret = PTR_ERR(ctx->typec.port);
ctx->typec.port = NULL;
dev_err(dev, "Failed to register type c port %d\n", ret);
return ret;
}
That makes it tricky to use no_free_ptr() so I wonder if this is
a case where the old fashioned fix of adding all the relevant
fwnode_handle_put() calls is the better option. The __free()
approach doesn't always fit.
Jonathan
> ---
> drivers/usb/typec/anx7411.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/usb/typec/anx7411.c b/drivers/usb/typec/anx7411.c
> index b12a07edc71b..9fb52f233a30 100644
> --- a/drivers/usb/typec/anx7411.c
> +++ b/drivers/usb/typec/anx7411.c
> @@ -16,6 +16,7 @@
> #include <linux/of_graph.h>
> #include <linux/of_platform.h>
> #include <linux/pm_runtime.h>
> +#include <linux/property.h>
> #include <linux/regulator/consumer.h>
> #include <linux/slab.h>
> #include <linux/types.h>
> @@ -1142,11 +1143,11 @@ static int anx7411_typec_port_probe(struct anx7411_data *ctx,
> {
> struct typec_capability *cap = &ctx->typec.caps;
> struct typec_params *typecp = &ctx->typec;
> - struct fwnode_handle *fwnode;
> const char *buf;
> int ret, i;
>
> - fwnode = device_get_named_child_node(dev, "connector");
> + struct fwnode_handle *fwnode __free(fwnode_handle)
> + = device_get_named_child_node(dev, "connector");
> if (!fwnode)
> return -EINVAL;
>
> @@ -1237,7 +1238,7 @@ static int anx7411_typec_port_probe(struct anx7411_data *ctx,
> typecp->caps_flags |= HAS_SINK_WATT;
> }
>
> - cap->fwnode = fwnode;
> + cap->fwnode = no_free_ptr(fwnode);
>
> ctx->typec.role_sw = usb_role_switch_get(dev);
> if (IS_ERR(ctx->typec.role_sw)) {
> --
> 2.45.1
>
