linux-kernel - Re: [PATCH v2 1/5] usb: xhci: Disable slot even virt-dev is null

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Date:   Thu, 10 Aug 2017 13:00:04 +0300
From:   Mathias Nyman <mathias.nyman@...ux.intel.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        zhengjun.xing@...ux.intel.com,
        Guoqing Zhang <guoqing.zhang@...el.com>
Subject: Re: [PATCH v2 1/5] usb: xhci: Disable slot even virt-dev is null

On 10.08.2017 03:35, Lu Baolu wrote:
> Hi,
>
> On 08/09/2017 03:58 PM, Mathias Nyman wrote:
>> On 27.07.2017 05:21, Lu Baolu wrote:
>>> xhci_disable_slot() is a helper for disabling a slot when a device
>>> goes away or recovers from error situations. Currently, it checks
>>> the corespoding virt-dev pointer and returns directly (w/o issuing
>>> disable slot command) if it's null.
>>>
>>> This is unnecessary and will cause problems in case where virt-dev
>>> allocation fails and xhci_disable_slot() is called to roll back the
>>> hardware state. Refer to the implementation of xhci_alloc_dev().
>>>
>>
>> True, checking for xhci->devs[slot_id] doesn't work if xhci_alloc_dev()
>> failed xhci_alloc_virt_device() and calls xhci_disable_slot,
>>
>> but the virt dev check is needed for test mode, which will just try
>> to disable all slots from 1 to HCS_MAX_SLOTS:
>>
>>   xhci_enter_test_mode(..)
>>         /* Disable all Device Slots */
>>      for (i = 1; i <= HCS_MAX_SLOTS(xhci->hcs_params1); i++) {
>>                  retval = xhci_disable_slot(xhci, NULL, i);
>>
>>
>
> So, how about checking virt dev before this invoking?
>
> @@ -612,10 +612,12 @@ static int xhci_enter_test_mode(struct xhci_hcd *xhci,
>          xhci_dbg(xhci, "Disable all slots\n");
>          spin_unlock_irqrestore(&xhci->lock, *flags);
>          for (i = 1; i <= HCS_MAX_SLOTS(xhci->hcs_params1); i++) {
> -               retval = xhci_disable_slot(xhci, NULL, i);
> -               if (retval)
> -                       xhci_err(xhci, "Failed to disable slot %d, %d. Enter test mode anyway\n",
> -                                i, retval);
> +               if (xhci->devs[i]) {
> +                       retval = xhci_disable_slot(xhci, NULL, i);
> +                       if (retval)
> +                               xhci_err(xhci, "Failed to disable slot %d, %d. Enter test mode anyway\n",
> +                                        i, retval);
> +               }


Yes, something like this will work

Thanks
Mathias