Re: [PATCH v5] perf: arm_cspmu: Separate Arm and vendor module

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On 2023-08-19 21:11, Besar Wicaksono wrote:
+void arm_cspmu_impl_unregister(const struct arm_cspmu_impl_match
+     struct device *dev;
+     struct arm_cspmu_impl_match *match;
+     match = arm_cspmu_impl_match_get(impl_match->pmiidr_val);
+     WARN_ON(!match);

Nit: do "if (WARN_ON(!match)) return;" rather than indenting almost the whole function.

+     if (match) {
+             /* Unbind the driver from all matching backend devices. */
+             dev = driver_find_device(&arm_cspmu_driver.driver, NULL,
+                     match, arm_cspmu_match_device);
+             if (dev) {
+                     device_release_driver(dev);
+                     goto dev_release;
+             }

minor nit: We could simply do :

static int arm_cspmu_release_driver(struct device *dev, void *data)
         struct arm_cspmu *cspmu =

         if (cspmu && cspmu->impl.match == match)
         return 0;

                 ret = driver_for_each_device(&driver, NULL, match,

It doesn’t seem to work for me.
Is it safe to release while iterating via driver_for_each_device ?

Looking at the klist code it doesn't *obviously* appear safe to modify the list during iteration, so probably best not to risk it anyway. However, please try to write this loop as an actual loop, e.g.:

	while ((dev = driver_find_device()))

At first glance I thought there was a bug here that it's only processing a single device, then eventually I saw the goto and my thought changed to "Eww..."


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