[PATCH] usbfs: Increase arbitrary limit for USB 3 isopkt length

[PATCH] usbfs: Increase arbitrary limit for USB 3 isopkt length

[Federico Manzan]

Increase the current arbitrary limit for isocronous packet size to a
value large enough to account for USB 3.0 super bandwidth streams,
bMaxBurst (0~15 allowed, 1~16 packets)
bmAttributes (bit 1:0, mult 0~2, 1~3 packets)
so the size max for one USB 3 isocronous transfer is
1024 byte * 16 * 3 = 49152 byte

Signed-off-by: Federico Manzan <f.manzan@gmail.com>
---
 drivers/usb/core/devio.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index caefc80..7ac137e 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -1287,9 +1287,11 @@ static int proc_do_submiturb(struct dev_state *ps, struct usbdevfs_urb *uurb,
 			goto error;
 		}
 		for (totlen = u = 0; u < uurb->number_of_packets; u++) {
-			/* arbitrary limit,
-			 * sufficient for USB 2.0 high-bandwidth iso */
-			if (isopkt[u].length > 8192) {
+			/* arbitrary limit need for USB 3.0
+			 * bMaxBurst (0~15 allowed, 1~16 packets)
+			 * bmAttributes (bit 1:0, mult 0~2, 1~3 packets)
+			 * sizemax: 1024 * 16 * 3 = 49152*/
+			if (isopkt[u].length > 65536) {
 				ret = -EINVAL;
 				goto error;
 			}
-- 
1.7.10.4

Re: [PATCH] usbfs: Increase arbitrary limit for USB 3 isopkt length

[Alan Stern]

On Fri, 24 May 2013, Federico Manzan wrote:

> Increase the current arbitrary limit for isocronous packet size to a
> value large enough to account for USB 3.0 super bandwidth streams,
> bMaxBurst (0~15 allowed, 1~16 packets)
> bmAttributes (bit 1:0, mult 0~2, 1~3 packets)
> so the size max for one USB 3 isocronous transfer is
> 1024 byte * 16 * 3 = 49152 byte
> 
> Signed-off-by: Federico Manzan <f.manzan@gmail.com>

So you decided to take matters into your own hands.  Good for you!

> diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
> index caefc80..7ac137e 100644
> --- a/drivers/usb/core/devio.c
> +++ b/drivers/usb/core/devio.c
> @@ -1287,9 +1287,11 @@ static int proc_do_submiturb(struct dev_state *ps, struct usbdevfs_urb *uurb,
>  			goto error;
>  		}
>  		for (totlen = u = 0; u < uurb->number_of_packets; u++) {
> -			/* arbitrary limit,
> -			 * sufficient for USB 2.0 high-bandwidth iso */
> -			if (isopkt[u].length > 8192) {
> +			/* arbitrary limit need for USB 3.0
> +			 * bMaxBurst (0~15 allowed, 1~16 packets)
> +			 * bmAttributes (bit 1:0, mult 0~2, 1~3 packets)
> +			 * sizemax: 1024 * 16 * 3 = 49152*/
> +			if (isopkt[u].length > 65536) {
>  				ret = -EINVAL;
>  				goto error;
>  			}

A couple of suggestions for improvements:

First, new or updated multi-line comments should follow the accepted
formatting standard:

	/*
	 * Start comment here...
	 * and end here.
	 */

Second, it's confusing for the comment to mention that the limit is
49152 and the code to set the limit to 65536.  They should agree on a
single value (probably 49152).

If you make those two changes, you can add

Acked-by: Alan Stern <stern@rowland.harvard.edu>

Alan Stern

Re: [PATCH] usbfs: Increase arbitrary limit for USB 3 isopkt length

[Sergei Shtylyov]

Hello.

On 24-05-2013 12:47, Federico Manzan wrote:

> Increase the current arbitrary limit for isocronous packet size to a
> value large enough to account for USB 3.0 super bandwidth streams,
> bMaxBurst (0~15 allowed, 1~16 packets)
> bmAttributes (bit 1:0, mult 0~2, 1~3 packets)
> so the size max for one USB 3 isocronous transfer is
> 1024 byte * 16 * 3 = 49152 byte

> Signed-off-by: Federico Manzan <f.manzan@gmail.com>
> ---
>   drivers/usb/core/devio.c |    8 +++++---
>   1 file changed, 5 insertions(+), 3 deletions(-)

> diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
> index caefc80..7ac137e 100644
> --- a/drivers/usb/core/devio.c
> +++ b/drivers/usb/core/devio.c
> @@ -1287,9 +1287,11 @@ static int proc_do_submiturb(struct dev_state *ps, struct usbdevfs_urb *uurb,
>   			goto error;
>   		}
>   		for (totlen = u = 0; u < uurb->number_of_packets; u++) {
> -			/* arbitrary limit,
> -			 * sufficient for USB 2.0 high-bandwidth iso */
> -			if (isopkt[u].length > 8192) {
> +			/* arbitrary limit need for USB 3.0
> +			 * bMaxBurst (0~15 allowed, 1~16 packets)
> +			 * bmAttributes (bit 1:0, mult 0~2, 1~3 packets)
> +			 * sizemax: 1024 * 16 * 3 = 49152*/

    The preferred style of the multi-line comments is this:

/*
  * bla
  * bla
  */

WBR, Sergei

Re: [PATCH] usbfs: Increase arbitrary limit for USB 3 isopkt length

[Federico Manzan]

On 05/24/2013 03:51 PM, Alan Stern wrote:
>> diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
>> index caefc80..7ac137e 100644
>> --- a/drivers/usb/core/devio.c
>> +++ b/drivers/usb/core/devio.c
>> @@ -1287,9 +1287,11 @@ static int proc_do_submiturb(struct dev_state *ps, struct usbdevfs_urb *uurb,
>>   			goto error;
>>   		}
>>   		for (totlen = u = 0; u<  uurb->number_of_packets; u++) {
>> -			/* arbitrary limit,
>> -			 * sufficient for USB 2.0 high-bandwidth iso */
>> -			if (isopkt[u].length>  8192) {
>> +			/* arbitrary limit need for USB 3.0
>> +			 * bMaxBurst (0~15 allowed, 1~16 packets)
>> +			 * bmAttributes (bit 1:0, mult 0~2, 1~3 packets)
>> +			 * sizemax: 1024 * 16 * 3 = 49152*/
>> +			if (isopkt[u].length>  65536) {
>>   				ret = -EINVAL;
>>   				goto error;
>>   			}
> A couple of suggestions for improvements:
>
> First, new or updated multi-line comments should follow the accepted
> formatting standard:
>
> 	/*
> 	 * Start comment here...
> 	 * and end here.
> 	 */
ok, I change the comment in the suggested way
> Second, it's confusing for the comment to mention that the limit is
> 49152 and the code to set the limit to 65536.  They should agree on a
> single value (probably 49152).
>
In the USB 2 isochronous the limit is 1024 byte x 3 pkts = 3072, but in 
the code is write 8192. I don't understand why, for the memory page 
size? for have a tolerant limits? for rounding to a nice number?
So I wrote a limit some more big and round, but I agree with you the 
best way is write the correct limit, so I modify in this way, soon.

Federico Manzan