On 1/24/20 3:57 PM, Frank Rowand wrote:
> On 1/7/20 2:11 AM, Geert Uytterhoeven wrote:
>> Hi Frank,
>>
>> On Tue, Jan 7, 2020 at 8:10 AM Frank Rowand <frowand.list@xxxxxxxxx> wrote:
>>> On 1/6/20 5:34 PM, Frank Rowand wrote:
>>>> On 12/30/19 7:38 AM, Geert Uytterhoeven wrote:
>>>>> As GPIO hogs are configured at GPIO controller initialization time,
>>>>> adding/removing GPIO hogs in DT overlays does not work.
>>>>>
>>>>> Add support for GPIO hogs described in DT overlays by registering an OF
>>>>> reconfiguration notifier, to handle the addition and removal of GPIO hog
>>>>> subnodes to/from a GPIO controller device node.
>>>>>
>>>>> Note that when a GPIO hog device node is being removed, its "gpios"
>>>>> properties is no longer available, so we have to keep track of which
>>>>> node a hog belongs to, which is done by adding a pointer to the hog's
>>>>> device node to struct gpio_desc.
>>>>
>>>> If I have read the patches and the existing overlay source correctly,
>>>> then some observations:
>>>>
>>>> - A gpio hog node added in an overlay will be properly processed.
>>>>
>>>> - A gpio hog node already existing in the live devicetree, but with a
>>>> non-active status will be properly processed if the status of the
>>>> gpio hog node is changed to "ok" in the overlay.
>
> Verified by testing.
>
>
>>>> - If a gpio hog node already exists in the live devicetree with an
>>>> active status, then any updated or added properties in that gpio
>>>> hog node in the overlay will have no effect.
>
> Should be documented.
>
>
>>>> There is a scenario where the updated property would have an effect:
>>>> apply a second overlay that sets the status to inactive, then apply
>>>> a third overlay that sets the status back to active. This is a
>>>> rather contrived example and I think it should be documented as
>>>> not supported and the result undefined.
>
> I was wrong in this case.
>
> of_reconfig_get_state_change() does not simply report whether a node
> is added or removed, which confused me because it returns
> OF_RECONFIG_CHANGE_ADD and OF_RECONFIG_CHANGE_REMOVE (as well as
> no change), which I was incorrectly translating to node added or
> node removed. OF_RECONFIG_CHANGE_ADD and OF_RECONFIG_CHANGE_REMOVE
> properly report a node becoming available or available due to changes
^^^^^^^^^^^^
or unavailable
> in the "status" property, as well as accounting for a node being
> added or removed.
>
> So the case that I was worried about is handled correctly.
>
>
>>> I went back and double checked the related code. For gpio hog nodes
>>> that are in a non-overlay, the status property is checked because
>>> of_gpiochip_scan_gpios() uses for_each_available_child_of_node()
>>> to search for gpio hog nodes, and for_each_available_child_of_node()
>>> checks the status property. But in the case of a gpio hog node
>>> added by an overlay, of_gpio_notify() does not check the status
>>> property in the gpio hog node. The check for the status property
>>> should be added to of_gpio_notify().
>>
>> Right. of_device_is_available() should be called to check this.
>> Note that of_i2c_notify() and of_spi_notify() also lack such a check.
>> of_platform_notify() calls of_platform_device_create_pdata(), which does
>> have the check.
>
> And thus I was wrong about this also, so of_gpio_notify() does not need to
> check the status property, since of_reconfig_get_state_change() already
> implicitly incorporates this check.
>
>>
>> Gr{oetje,eeting}s,
>>
>> Geert
>>
>
>
