linux-kernel - Re: [PATCH] usb: gadget: u_ether: Set is

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Message-ID: <bf19304a-c9b7-4647-b33f-cf5e771cfa83@oss.qualcomm.com>
Date: Fri, 14 Feb 2025 14:24:31 +0530
From: Prashanth K <prashanth.k@....qualcomm.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Ferry Toth <ftoth@...londelft.nl>,
        Ricardo B Marliere <ricardo@...liere.net>, Kees Cook <kees@...nel.org>,
        linux-usb@...r.kernel.org, Elson Roy Serrao <quic_eserrao@...cinc.com>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] usb: gadget: u_ether: Set is_suspend flag if remote
 wakeup fails



On 14-02-25 01:30 pm, Greg Kroah-Hartman wrote:
> On Wed, Feb 12, 2025 at 03:38:40PM +0530, Prashanth K wrote:
>> Currently while UDC suspends, u_ether attempts to remote wakeup
>> the host if there are any pending transfers. However, if remote
>> wakeup fails, the UDC remains suspended but the is_suspend flag
>> is not set. And since is_suspend flag isn't set, the subsequent
>> eth_start_xmit() would queue USB requests to suspended UDC.
>>
>> To fix this, bail out from gether_suspend() only if remote wakeup
>> operation is successful.
>>
>> Cc: stable@...r.kernel.org
>> Fixes: 0a1af6dfa077 ("usb: gadget: f_ecm: Add suspend/resume and remote wakeup support")
>> Signed-off-by: Prashanth K <prashanth.k@....qualcomm.com>
>> ---
>>  drivers/usb/gadget/function/u_ether.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c
>> index 09e2838917e2..f58590bf5e02 100644
>> --- a/drivers/usb/gadget/function/u_ether.c
>> +++ b/drivers/usb/gadget/function/u_ether.c
>> @@ -1052,8 +1052,8 @@ void gether_suspend(struct gether *link)
>>  		 * There is a transfer in progress. So we trigger a remote
>>  		 * wakeup to inform the host.
>>  		 */
>> -		ether_wakeup_host(dev->port_usb);
>> -		return;
>> +		if (!ether_wakeup_host(dev->port_usb))
>> +			return;
> 
> What about the other place in the driver where this function is called
> but the return value is ignored?
> 
> thanks,
> 
> greg k-h

Other than above one, eth_start_xmit() tries to remote wakeup host when
we have some data to send from n/w layer. In that case we try to wakeup
host and directly return NETDEV_TX_BUSY to caller. If remote wakeup
succeeds, then resume() would call netif_start_queue() which again lets
n/w layer to queue skb. Hence we don't have to check for ret of
ether_wakeup_host() in that case.

Regards,
Prashanth K