Hi,
On 10/09/2013 10:55 AM, Gerd Hoffmann wrote:
On Di, 2013-10-08 at 21:58 +0200, Hans de Goede wrote:
If we detach the kernel drivers on the first set_config, then they will
be still attached when the device gets its initial reset. Causing the drivers
to re-initialize the device after the reset, dirtying the device state.
@@ -1051,7 +1055,6 @@ static void usb_host_set_config(USBHostDevice *s, int
config, USBPacket *p)
trace_usb_host_set_config(s->bus_num, s->addr, config);
usb_host_release_interfaces(s);
- usb_host_detach_kernel(s);
rc = libusb_set_configuration(s->dh, config);
if (rc != 0) {
usb_host_libusb_error("libusb_set_configuration", rc);
Sure we can safely remove the detach_kernel here?
Yes.
Assuming we have a device with multiple configurations, each
configuration has a different set of interfaces, guest switches from one
config to another. Do we correctly unbind kernel / claim interfaces
then?
Yes we still have a usb_host_detach_kernel() call in the beginning
of usb_host_claim_interfaces(), which gets run on the new interfaces
immediately after the libusb_set_configuration call.
Doing a detach_kernel after a set_config has always been necessary,
since the kernel will automatically bind drivers to the new interfaces
if the set_config succeeds.
Doing detach_kernel before set_config is necessary if kernel drivers
are attached, because the kernel will not allow a set_config if any
drivers are bound. But we already do a set_config for the current
config on usb_host_open() now, and if a new config gets installed we
immediately detach the kernel drivers again from usb_host_claim_interfaces()
so when we enter usb_host_set_config no kernel drivers, other then
usbfs (the userspace access driver) will be attached, and usbfs is
detached by releasing the interfaces (*).
Regards,
Hans
*) In recent libusb versions libusb will even disallow using
libusb_detach_kernel_driver to detach usbfs, so as to stop a user space
program from breaking anothers userspaces program claim on the interface
by completelty detaching usbfs from the interface.
