Re: [PATCH v3] usb: core: verify devicetree nodes for USB devices

From: Måns Rullgård
Date: Mon May 13 2019 - 06:08:13 EST

Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> writes:

> Hi Peter,
> On 2019-05-13 11:23, Peter Chen wrote:
>>> On 2019-05-13 11:00, Peter Chen wrote:
>>>>> On 2019-05-10 05:10, Peter Chen wrote:
>>>>>>> Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> writes:
>>>>>>>> Commit 69bec7259853 ("USB: core: let USB device know device node")
>>>>>>>> added support for attaching devicetree node for USB devices. The
>>>>>>>> mentioned commit however identifies the given USB device node only
>>>>>>>> by the
>>>>> 'reg'
>>>>>>>> property in the host controller children nodes. The USB device
>>>>>>>> node however also has to have a 'compatible' property as described
>>>>>>>> in Documentation/devicetree/bindings/usb/usb-device.txt. Lack for
>>>>>>>> the 'compatible' property check might result in assigning a
>>>>>>>> devicetree node, which is not intended to be the proper node for the given
>>> USB device.
>>>>>>>> This is important especially when USB host controller has
>>>>>>>> child-nodes for other purposes. For example, Exynos EHCI and OHCI
>>>>>>>> drivers already define child-nodes for each physical root hub port
>>>>>>>> and assigns respective PHY controller and parameters for them.
>>>>>>>> Those binding predates support for USB devicetree nodes.
>>>>>>>> Checking for the proper compatibility string allows to mitigate
>>>>>>>> the conflict between USB device devicetree nodes and the bindings
>>>>>>>> for USB controllers with child nodes. It also fixes the
>>>>>>>> side-effect of the other commits, like 01fdf179f4b0 ("usb: core:
>>>>>>>> skip interfaces disabled in devicetree"), which incorrectly
>>>>>>>> disables some devices on Exynos based boards.
>>>>>> Hi Marek,
>>>>>> The purpose of your patch is do not set of_node for device under USB
>>>>>> controller,
>>>>> right?
>>>>> Right.
>>>> Do you mind doing it at function exynos_ehci_get_phy of ehci-exynos.c?
>>> I don't mind fixing it in ehci-exynos, but frankly so far I have no
>>> idea how to do it. The problem is that newly created USB devices
>>> get of-node pointer pointing to a node which if not intended for
>>> them. How this can be fixed in ehci-exynos?
>> Can't be workaround by setting of_node as NULL for EHCI controller or
>> for PHY node at exynos_ehci_get_phy?
> Ah, such workaround? I will check, but this will need to be done with
> care, because have a side effect for other subsystems like regulators or
> clocks.
> BTW, What's wrong with proper, full verification of USB device nodes?

Your approach so far doesn't address the actual problem of a conflict
between the generic USB DT bindings and those for the Exynos host
controller. If you fix that, the validation issue goes away.

Måns Rullgård