linux-kernel - Re: [PATCH] usb:cdns3: Fix for CV CH9 running with g

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Date:   Wed, 9 Oct 2019 16:50:48 +0300
From:   Roger Quadros <rogerq@...com>
To:     Pawel Laszczak <pawell@...ence.com>,
        Felipe Balbi <felipe.balbi@...ux.intel.com>,
        Peter Chen <peter.chen@....com>
CC:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "jbergsagel@...com" <jbergsagel@...com>,
        "nsekhar@...com" <nsekhar@...com>, "nm@...com" <nm@...com>,
        Suresh Punnoose <sureshp@...ence.com>,
        Rahul Kumar <kurahul@...ence.com>
Subject: Re: [PATCH] usb:cdns3: Fix for CV CH9 running with g_zero driver.

Pawel,

On 09/10/2019 06:58, Pawel Laszczak wrote:
> Hi,
> 
>>
>> Hi,
>>
>> Peter Chen <peter.chen@....com> writes:
>>> On 19-10-07 07:39:11, Pawel Laszczak wrote:
>>>> Patch fixes issue with Halt Endnpoint Test observed
>>>
>>> %s/Endnpoint/Endpoint
>>>
>>>>
>>>> during using g_zero
>>>> driver as DUT. Bug occurred only on some testing board.
>>>
>>> g_zero is legacy, please use configfs function source_sink or loopback
>>> instead.
>>
>> We still want fixes for those ;-)
> 
> So, if my understanding is correct in new production systems
> using legacy gadget drivers is not recommended and we are not going to fix
> any more bugs there.

We can't really control who uses what. So we need to support legacy
drivers as well.

The issue detected by using g_zero is a controller driver issue and not an
issue with g_zero itself.

cheers,
-roger

> 
> The legacy gadget drivers remains in the kernel only to support the old
> products.
> 
> So because we introduce new driver we should not worry  about legacy
> gadget drivers.
> 
> Is my understanding correct ?
> 
> pawell
>   
>>
>>>> Endpoint can defer transition to Halted state if endpoint has pending
>>>> requests.
>>>
>>> The implementation of halt handling is a little complicated, you may
>>> consider return -EAGAIN for functional stall through usb_ep_set_halt
>>> from function driver if the requests are pending, it doesn't need to
>>> defer such kinds of functional stall.
>>
>> -EAGAIN, IIRC is only supposed to be used for IN endpoint stalls.
>>
>> --
>> balbi

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