On Fri, 2 Jan 2009, Alon Bar-Lev wrote:
ifd_sysdep_usb_set_interface(dev,
params->usb.interface,
params->usb.altsetting))
A usb device may provide multiple programming interfaces to its
underlying functionality. This call selects the one we want to use.
I could not find calls to RESET, RESETEP and SETINTERFACE in libusb-1,
so I guess normal applications should not use these?
libusb refers to these as IOCTL_USB_RESET, IOCTL_USB_RESETEP, and
IOCTL_USB_SETINTF
This patch should help. It avoids changing the altsetting if there is only
one, which makes it somewhat safe to skip. I don't really like this idea,
since unlike SETCONFIGURATION, there is not really a good reason to avoid
using SETINTERFACE.
It's actually possible that doing the SETCONFIGURATION would make your
device behave better, but we can't put it back without adding alot of
probing to make sure it will work.
Index: ifd-ccid.c
===================================================================
--- ifd-ccid.c (revision 1094)
+++ ifd-ccid.c (working copy)
@@ -477,7 +477,7 @@
{
ccid_status_t *st;
ifd_device_params_t params;
- int r, i, c, ifc, alt;
+ int r, i, c, ifc, alt, num_alt;
struct ifd_usb_device_descriptor de;
struct ifd_usb_config_descriptor conf;
struct ifd_usb_interface_descriptor *intf;
@@ -516,8 +516,8 @@
continue;
for (ifc = 0; ifc < conf.bNumInterfaces; ifc++) {
- for (alt = 0; alt < conf.interface[ifc].num_altsetting;
- alt++) {
+ num_alt = conf.interface[ifc].num_altsetting;
+ for (alt = 0; alt < num_alt; alt++) {
int typeok = 0;
int ok = 0;
intf = &conf.interface[ifc].altsetting[alt];
@@ -646,7 +646,10 @@
params.usb.configuration = -1;
params.usb.interface = intf->bInterfaceNumber;
- params.usb.altsetting = intf->bAlternateSetting;
+ if (num_alt > 1 || intf->bAlternateSetting > 0)
+ params.usb.altsetting = intf->bAlternateSetting;
+ else
+ params.usb.altsetting = -1;
r = ccid_parse_descriptor(&ccid, p, r - i);
ifd_usb_free_configuration(&conf);
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