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SubjectRe: [07/18] thunderbolt: Handle rejected Thunderbolt devices
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On 2018-02-27 1:26 AM, Mika Westerberg wrote:
> On Mon, Feb 26, 2018 at 12:15:28PM -0800, Jeremy McNicoll wrote:
>> On 2018-02-26 11:46 AM, Mika Westerberg wrote:
>>> On Mon, Feb 26, 2018 at 11:28:16AM -0800, Jeremy McNicoll wrote:
>>>> On 2018-02-26 5:38 AM, Mika Westerberg wrote:
>>>>> On Mon, Feb 26, 2018 at 12:20:29PM +0200, Mika Westerberg wrote:
>>>>>> On Thu, Feb 22, 2018 at 03:17:38PM -0800, Jeremy McNicoll wrote:
>>>>>>>> + if (pkg->link_info & ICM_LINK_INFO_REJECTED) {
>>>>>>>> + tb_info(tb, "switch at %u.%u was rejected by ICM firmware\n",
>>>>>>>> + link, depth);
>>>>>>>
>>>>>>> This kind of condition sounds more like an error instead of info.
>>>>>>> Please bump this up to tb_WARN/tb_warn ideally tb_err().
>>>>>>
>>>>>> No, this is not an error.
>>>>>
>>>>> To be more clear, it is totally fine to have the firmware to reject some
>>>>> devices. For example in case of the new usbonly security level the
>>>>> firmware rejects other devices but the first.
>>>>>
>>>>
>>>> Ok. Is that kind of information available to the kernel? What security
>>>> mode we are in?
>>>>
>>>> ie) if (LINK_REJECTED && !USB_SECURITY)
>>>> print "Error switch %u was rejected since its not usbonly"
>>>> endif
>>>>
>>>> I am sure something like that simplified pseudo code above would
>>>> be somewhat useful to users when debugging.
>>>
>>> That's why it is on info level so it goes to dmesg but does not scare
>>> the user :-)
>>>
>>
>> The point I am trying to make is that it would be nice to be able to
>> know WHY the link was rejected and not just that it was rejected.
>
> Fair enough. In practice (since we ask the firmware to accept any
> device) the only reason for rejection is that the topology limit is
> exceeded (too many devices in the chain).
>
> I'm thinking to change the message to something like:
>
> tb_info(tb, "switch at %u.%u was rejected by ICM firmware because topology limit exceeded\n",
> link, depth);
>
> And do the same for Titan Ridge in patch [18/18].
>
> Security level can be read directly from "security" sysfs attribute of
> the domain so that information does not need to be duplicated IMHO.
>
> Does that work for you?
>


Sounds good to me.



-jeremy

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