Re: [PATCH v5 2/4] iio: core: Introduce IIO configfs support

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On 05/04/2015 10:59 PM, Lars-Peter Clausen wrote:
On 05/04/2015 12:50 PM, Daniel Baluta wrote:
This creates an IIO configfs subystem named "iio", with a default
"triggers"
group.

Triggers group is used for handling software triggers. To create a new
software
trigger one must create a directory inside the trigger directory.

Software trigger name MUST follow the following convention:
    * <trigger-type>-<trigger-name>
Where:
    * <trigger_type>, specifies the interrupt source (e.g: hrtimer)
    * <trigger-name>, specifies the IIO device trigger name

Failing to follow this convention will result in an directory creation
error.

E.g, assuming that hrtimer trigger type is registered with IIO software
trigger core:

$ mkdir /config/iio/triggers/hrtimer-instance1


Nice, short and clean. Looks pretty good. It's a bit of a shame that we
can't have a per type directory, but if that's how configfs works I
guess there is not much choice.

[...]
+static struct config_group *trigger_make_group(struct config_group
*group,
+                           const char *name)
+{
+    char *type_name;
+    char *trigger_name;
+    char buf[MAX_NAME_LEN];
+    struct iio_sw_trigger *t;
+
+    snprintf(buf, MAX_NAME_LEN, "%s", name);
+
+    /* group name should have the form <trigger-type>-<trigger-name> */
+    type_name = buf;
+    trigger_name = strchr(buf, '-');
+    if (!trigger_name) {
+        pr_err("Unable to locate '-' in %s. Use <type>-<name>.\n", buf);

Do we want to print this side channel message? Makes it pretty easy to
spam the kernel log with a rouge application.

I think this is useful, people can get crazy for random -EINVAL errors :). Also the same is done in drivers/usb/gadget/configfs.c.



+        return ERR_PTR(-EINVAL);
+    }
+
+    /* replace - with \0, this nicely separates the two strings */
+    *trigger_name = '\0';
+    trigger_name++;
+
+    t = iio_sw_trigger_create(type_name, trigger_name);
+    if (IS_ERR(t))
+        return ERR_CAST(t);
+
+    config_item_set_name(&t->group.cg_item, name);
+
+    return &t->group;
+}
+
+static void trigger_drop_group(struct config_group *group,
+                   struct config_item *item)
+{
+    struct iio_sw_trigger *t = to_iio_sw_trigger(item);
+
+    if (t)

t will never be NULL.

Agree, will fix in v6.

+        iio_sw_trigger_destroy(t);
+    config_item_put(item);
+}

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