linux-kernel - Re: [RFC PATCH 1/5] usb: core: hcd: Modularize HCD stop configuration in usb_stop

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Date:   Tue, 24 Aug 2021 20:48:45 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     Mathias Nyman <mathias.nyman@...el.com>,
        Alan Stern <stern@...land.harvard.edu>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <chris.chiu@...onical.com>
Subject: Re: [RFC PATCH 1/5] usb: core: hcd: Modularize HCD stop configuration
 in usb_stop_hcd()

Hi Greg,

On 24/08/21 6:36 pm, Greg Kroah-Hartman wrote:
> On Tue, Aug 24, 2021 at 04:22:58PM +0530, Kishon Vijay Abraham I wrote:
>> No functional change. Since configuration to stop HCD is invoked from
>> multiple places, group all of them in usb_stop_hcd().
>>
>> Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
>> ---
>>  drivers/usb/core/hcd.c | 42 +++++++++++++++++++++++++-----------------
>>  1 file changed, 25 insertions(+), 17 deletions(-)
>>
>> diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
>> index 0f8b7c93310e..c036ba5311b3 100644
>> --- a/drivers/usb/core/hcd.c
>> +++ b/drivers/usb/core/hcd.c
>> @@ -2760,6 +2760,29 @@ static void usb_put_invalidate_rhdev(struct usb_hcd *hcd)
>>  	usb_put_dev(rhdev);
>>  }
>>  
>> +/**
>> + * usb_stop_hcd - Halt the HCD
>> + * @hcd: the usb_hcd that has to be halted
>> + *
>> + * Stop the timer and invoke ->stop() callback on the HCD
>> + */
>> +static void usb_stop_hcd(struct usb_hcd *hcd)
>> +{
>> +	if (!hcd)
>> +		return;
> 
> That's impossible to hit, so no need to check for it, right?

Patch 3 of this series adds support for registering roothub of shared
HCD. So after that patch there can be a case where shared_hcd is NULL.
The other option would be to check for non-null value in hcd and then
invoke usb_stop_hcd().

Thanks
Kishon