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SubjectRe: [PATCH 09/10] usb: Add USB subsystem notifications [ver #3]
Date

Hi,

Greg Kroah-Hartman <gregkh@linuxfoundation.org> writes:
> On Thu, Jun 06, 2019 at 10:55:24AM -0400, Alan Stern wrote:
>> On Thu, 6 Jun 2019, Greg Kroah-Hartman wrote:
>>
>> > On Thu, Jun 06, 2019 at 10:24:18AM -0400, Alan Stern wrote:
>> > > On Thu, 6 Jun 2019, David Howells wrote:
>> > >
>> > > > Add a USB subsystem notification mechanism whereby notifications about
>> > > > hardware events such as device connection, disconnection, reset and I/O
>> > > > errors, can be reported to a monitoring process asynchronously.
>> > >
>> > > USB I/O errors covers an awfully large and vague field. Do we really
>> > > want to include them? I'm doubtful.
>> >
>> > See the other patch on the linux-usb list that wanted to start adding
>> > KOBJ_CHANGE notifications about USB "i/o errors".
>>
>> That patch wanted to add notifications only for enumeration failures
>> (assuming you're talking about the patch from Eugeniu Rosca), not I/O
>> errors in general.
>
> Yes, sorry, I was thinking that as a "I/O failed in enumeration" :)
>
>> > So for "severe" issues, yes, we should do this, but perhaps not for all
>> > of the "normal" things we see when a device is yanked out of the system
>> > and the like.
>>
>> Then what counts as a "severe" issue? Anything besides enumeration
>> failure?
>
> Not that I can think of at the moment, other than the other recently
> added KOBJ_CHANGE issue. I'm sure we have other "hard failure" issues
> in the USB stack that people will want exposed over time.

From an XHCI standpoint, Transaction Errors might be one thing. They
happen rarely and are a strong indication that the bus itself is
bad. Either bad cable, misbehaving PHYs, improper power management, etc.

--
balbi
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