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

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Message-ID: <598AC09D.4070003@linux.intel.com>
Date:   Wed, 9 Aug 2017 10:58:21 +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 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);



> 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)
>