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 08:35:11 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Mathias Nyman <mathias.nyman@...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

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);
+               }
        }
        spin_lock_irqsave(&xhci->lock, *flags);
        /* Put all ports to the Disable state by clear PP */

Best regards,
Lu Baolu

>
>> This patch removes lines to check virt-dev in xhci_disable_slot().
>>
>> Fixes: f9e609b82479 ("usb: xhci: Add helper function xhci_disable_slot().")
>> Cc: Guoqing Zhang <guoqing.zhang@...el.com>
>> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
>> ---
>>   drivers/usb/host/xhci.c | 4 ----
>>   1 file changed, 4 deletions(-)
>>
>> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
>> index b2ff1ff..e69073f 100644
>> --- a/drivers/usb/host/xhci.c
>> +++ b/drivers/usb/host/xhci.c
>> @@ -3567,11 +3567,7 @@ int xhci_disable_slot(struct xhci_hcd *xhci, struct xhci_command *command,
>>       unsigned long flags;
>>       u32 state;
>>       int ret = 0;
>> -    struct xhci_virt_device *virt_dev;
>>
>> -    virt_dev = xhci->devs[slot_id];
>> -    if (!virt_dev)
>> -        return -EINVAL;
>>       if (!command)
>>           command = xhci_alloc_command(xhci, false, false, GFP_KERNEL);
>>       if (!command)
>>
>
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