linux-kernel - Re: [07/18] thunderbolt: Handle rejected Thunderbolt devices

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Message-ID: <6560a597-0075-549e-f723-1bc5eb54c7bc@redhat.com>
Date:   Mon, 26 Feb 2018 12:15:28 -0800
From:   Jeremy McNicoll <jmcnicol@...hat.com>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org,
        Andreas Noever <andreas.noever@...il.com>,
        Michael Jamet <michael.jamet@...el.com>,
        Yehezkel Bernat <yehezkel.bernat@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Mario.Limonciello@...l.com,
        Radion Mirchevsky <radion.mirchevsky@...el.com>
Subject: Re: [07/18] thunderbolt: Handle rejected Thunderbolt devices

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.