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USB: cdc-wdm: Avoid hanging on interface with no USB_CDC_DMM_TYPE

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The probe does not strictly require the USB_CDC_DMM_TYPE
descriptor, which is a good thing as it makes the driver
usable on non-conforming interfaces.  A user could e.g.
bind to it to a CDC ECM interface by using the new_id and
bind sysfs files.  But this would fail with a 0 buffer length
due to the missing descriptor.

Fix by defining a reasonable fallback size: The minimum
device receive buffer size required by the CDC WMC standard,
revision 1.1

Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Bjørn Mork 2012-01-20 01:49:57 +01:00 committed by Greg Kroah-Hartman
parent 8143a8963c
commit 7e3054a005
1 changed files with 3 additions and 1 deletions
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4
drivers/usb/class/cdc-wdm.c
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@ -57,6 +57,8 @@ MODULE_DEVICE_TABLE (usb, wdm_ids);
#define WDM_MAX 16
/* CDC-WMC r1.1 requires wMaxCommand to be "at least 256 decimal (0x100)" */
#define WDM_DEFAULT_BUFSIZE 256
static DEFINE_MUTEX(wdm_mutex);
@ -602,7 +604,7 @@ static int wdm_probe(struct usb_interface *intf, const struct usb_device_id *id)
struct usb_cdc_dmm_desc *dmhd;
u8 *buffer = intf->altsetting->extra;
int buflen = intf->altsetting->extralen;
u16 maxcom = 0;
u16 maxcom = WDM_DEFAULT_BUFSIZE;
if (!buffer)
goto out;