Hello Michael,
On 01/24/2010 10:20 PM, Michael S. Tsirkin wrote:
> On Sun, Jan 24, 2010 at 05:34:52PM +0100, Christian Krause wrote:
>> Resend. The patch was already sent to the list on 2009-12-11. It would
>> be great if it could be reviewed and applied. Thank you very much
>> in advance.
>>
>> The WLAN USB stick ZyXEL NWD271N (0586:3417) uses very large
>> usb control transfers of more than 2048 bytes which won't fit
>> into the buffer of the ctrl_struct. This results in an error message
>> "husb: ctrl buffer too small" and a non-working device.
>> Increasing the buffer size to 8192 seems to be a safe choice.
>>
>> Signed-off-by: Christian Krause <c...@plauener.de>
>
> Are there any drawbacks to make\ing the buffer larger?
I've roughly looked into the source code of usb-linux.c and I don't see
an issue if the buffer would be larger:
- if the buffer is used to get data via USBDEVFS_SUBMITURB from the
kernel then the check:
if (buffer_len > sizeof(s->ctrl.buffer)) {
fprintf(stderr, "husb: ctrl buffer too small (%u > %zu)\n",
buffer_len, sizeof(s->ctrl.buffer));
return USB_RET_STALL;
}
already ensures that the we only supply a buffer_len which matches the
buffer
- on the other hand, when we copy data out of the buffer into the data
structures from the HC, then there is also a check that we only copy as
much data as the HC requests:
if (len > p->len)
len = p->len;
memcpy(p->data, s->ctrl.buffer + s->ctrl.offset, len);
> If no, let's just make it 64K? IIUC that's a maximum
> length for control transfers as length is a 16 bit field.
I think that's OK since it looks like that the increase of memory would
only be 64k per usb host device.
Best regards,
Christian
>> ---
>> usb-linux.c | 2 +-
>> 1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/usb-linux.c b/usb-linux.c
>> index 285ac22..d205bd3 100644
>> --- a/usb-linux.c
>> +++ b/usb-linux.c
>> @@ -113,7 +113,7 @@ struct ctrl_struct {
>> uint16_t offset;
>> uint8_t state;
>> struct usb_ctrlrequest req;
>> - uint8_t buffer[2048];
>> + uint8_t buffer[8192];
>> };
>>
>> struct USBAutoFilter {
>> --
>> 1.6.2.5
>>
>>
>
