linux-kernel - Re: [PATCH] xhci: Remove unused value len from xhci_unmap_temp

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Message-ID: <3ad81fd6-e88e-f55b-fe82-ac7804bc354c@163.com>
Date:   Sun, 7 Mar 2021 09:14:26 +0800
From:   Zhangkun <zhangkun4jr@....com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Mathias Nyman <mathias.nyman@...el.com>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, Zhang Kun <zhangkun@...rlc.com>
Subject: Re: [PATCH] xhci: Remove unused value len from xhci_unmap_temp_buf

On 3/7/21 12:25 AM, Greg Kroah-Hartman wrote:
> On Sat, Mar 06, 2021 at 08:06:44PM +0800, zhangkun4jr@....com wrote:
>> From: Zhang Kun <zhangkun@...rlc.com>
>>
>> The value assigned to len by sg_pcopy_from_buffer() never used for
>> anything, so remove it.
>>
>> Signed-off-by: Zhang Kun <zhangkun@...rlc.com>
>> ---
>>  drivers/usb/host/xhci.c | 3 +--
>>  1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
>> index bd27bd670104..6ebda89d476c 100644
>> --- a/drivers/usb/host/xhci.c
>> +++ b/drivers/usb/host/xhci.c
>> @@ -1335,7 +1335,6 @@ static bool xhci_urb_temp_buffer_required(struct usb_hcd *hcd,
>>  
>>  static void xhci_unmap_temp_buf(struct usb_hcd *hcd, struct urb *urb)
>>  {
>> -	unsigned int len;
>>  	unsigned int buf_len;
>>  	enum dma_data_direction dir;
>>  
>> @@ -1351,7 +1350,7 @@ static void xhci_unmap_temp_buf(struct usb_hcd *hcd, struct urb *urb)
>>  				 dir);
>>  
>>  	if (usb_urb_dir_in(urb))
>> -		len = sg_pcopy_from_buffer(urb->sg, urb->num_sgs,
>> +		sg_pcopy_from_buffer(urb->sg, urb->num_sgs,
>>  					   urb->transfer_buffer,
>>  					   buf_len,
>>  					   0);
> 
> SHouldn't this be checked instead of ignored?
>

Hi, Greg.
Considering your tips I checked sg_pcopy_from_buffer(). it copys data
from urb->transfer_buffer to urb->sg, and only returns 0 or the 
'number of copied bytes', and seems to has no other exception branchs
that need to be checked. So I think it should be ingnored.

It may also be that I missed something, if that's the case, please
correct me.

Thanks,

Zhang