On 1/6/25 10:20 AM, Tudor Ambarus wrote:

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+static const struct acpm_handle *acpm_get_by_phandle(struct device_node *np,
+						     const char *property)
+{
+	struct acpm_handle *handle = NULL;
+	struct device_node *acpm_np;
+	struct acpm_info *info;
+
+	if (!np) {
+		pr_err("I need a device pointer\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	acpm_np = of_parse_phandle(np, property, 0);
+	if (!acpm_np)
+		return ERR_PTR(-ENODEV);
+
+	mutex_lock(&acpm_list_mutex);
+	list_for_each_entry(info, &acpm_list, node) {
+		if (acpm_np == info->dev->of_node) {
+			handle = &info->handle;
+			info->users++;
+			break;
+		}
+	}
+	mutex_unlock(&acpm_list_mutex);
+	of_node_put(acpm_np);
+

You also need device links and probably try_module_get. See clk.c
clk_hw_create_clk() or of_qcom_ice_get(). Interestingly, none of them
perform both operations, which I think is necessary.

I think you could also avoid entire list and mutex by using
platform_get_drvdata(), see of_qcom_ice_get().

[snip, irrelevant now]

I made my mind, I think the solution is threefold.
1/ use kref with a release callback so that the firmware drvdata will be
destroyed only when there are no consumers. Example:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1e7c57355a3bc617fc220234889e49fe722a6305

2/ In get_handle() after kref_get_unless_zero() succeeds, I'll be
calling try_module_get() for supplier. Even if kref will make sure that
consumers will still have a valid supplier drvdata, I'd like to delete
the supplier module when there are no consumers left.

3/ use device_link_add() so that when the supplier device unbinds, to
unbind the consumer devices as well.

I'll implement these. Cheers,
ta