linux-kernel - Re: [ 22/52] asix: Fix tx transfer padding for full-speed USB

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Date:	Thu, 10 May 2012 14:29:03 -0400
From:	Mark Lord <kernel@...savvy.com>
To:	Greg KH <gregkh@...uxfoundation.org>
CC:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Ingo van Lil <inguin@....de>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [ 22/52] asix: Fix tx transfer padding for full-speed USB

On 12-05-10 02:25 PM, Mark Lord wrote:
> On 12-05-10 01:31 PM, Greg KH wrote:
>> 3.3-stable review patch.  If anyone has any objections, please let me know.
> ..
>> From: Ingo van Lil <inguin@....de>
>> [ Upstream commit 2a5809499e35b53a6044fd34e72b242688b7a862 ]
>>
>> The asix.c USB Ethernet driver avoids ending a tx transfer with a zero-
>> length packet by appending a four-byte padding to transfers whose length
>> is a multiple of maxpacket. However, the hard-coded 512 byte maxpacket
>> length is valid for high-speed USB only; full-speed USB uses 64 byte
>> packets.
>>
>> Signed-off-by: Ingo van Lil <inguin@....de>
>> Signed-off-by: David S. Miller <davem@...emloft.net>
>> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> ---
>>  drivers/net/usb/asix.c |    4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> --- a/drivers/net/usb/asix.c
>> +++ b/drivers/net/usb/asix.c
>> @@ -403,7 +403,7 @@ static struct sk_buff *asix_tx_fixup(str
>>  	u32 packet_len;
>>  	u32 padbytes = 0xffff0000;
>>  
>> -	padlen = ((skb->len + 4) % 512) ? 0 : 4;
>> +	padlen = ((skb->len + 4) & (dev->maxpacket - 1)) ? 0 : 4;
>>  
>>  	if ((!skb_cloned(skb)) &&
>>  	    ((headroom + tailroom) >= (4 + padlen))) {
>> @@ -425,7 +425,7 @@ static struct sk_buff *asix_tx_fixup(str
>>  	cpu_to_le32s(&packet_len);
>>  	skb_copy_to_linear_data(skb, &packet_len, sizeof(packet_len));
>>  
>> -	if ((skb->len % 512) == 0) {
>> +	if (padlen) {
>>  		cpu_to_le32s(&padbytes);
>>  		memcpy(skb_tail_pointer(skb), &padbytes, sizeof(padbytes));
>>  		skb_put(skb, sizeof(padbytes));
>>
>>
> 
> This patch changes behaviour even for high-speed USB.
> Was this intentional, and why?

Never mind.. I missed the skb_push(skb, 4) line
that the diff doesn't show above.

Okay by me.

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