Hi Chris,
On 03/11/2014 05:27 PM, Chris Dickens wrote:
Hi Hans,
Are you sure this is what was happening ? Can you perhaps try again with
a printf added at a strategic place to ensure this is really what is going
on?
Here's the debug output right after the DISCONNECT_CLAIM fails:
[ 0.004913] [00007d79] libusb: debug [libusb_claim_interface] interface 1
[ 0.004930] [00007d79] libusb: debug [detach_kernel_driver_and_claim] ioctl
DISCONNECT_CLAIM error -1 errno 22
Looking at:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/usb/core/devio.c?id=22763c5cf3690a681551162c15d34d935308c8d7
(22763c5c is the commit id responding to the v2.6.32 tag)
I see the following in there:
static int usbdev_ioctl(struct inode *inode, struct file *file,
unsigned int cmd, unsigned long arg)
{
struct dev_state *ps = file->private_data;
struct usb_device *dev = ps->dev;
void __user *p = (void __user *)arg;
int ret = -ENOTTY;
...
switch (cmd) {
case USBDEVFS_CONTROL:
...
}
return ret;
}
This code path is used for calls from both 64 bit and 32 bit userspace apps,
so 32 bit apps should see -ENOTTY to for an unknown cmd code.
The code for RHEL's 2.6.32 kernel is a bit different, but essentially boils
down to the same thing. (I was referencing
http://ftp.redhat.com/redhat/linux/enterprise/6Workstation/en/os/SRPMS/kernel-2.6.32-431.5.1.el6.src.rpm)
Doing a bit more research, I've found this is actually happening further up the
call stack, before usbfs is ever involved. I noticed this in the kernel log:
ioctl32(pcs:32121): Unknown cmd fd(11) cmd(8108551b){t:'U';sz:264}
arg(f59b4c50) on /dev/bus/usb/001/079
This message is generating from
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/fs/compat_ioctl.c?id=22763c5cf3690a681551162c15d34d935308c8d7#n2769
This is called from inside the compat_sys_ioctl function
(https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/fs/compat_ioctl.c?id=22763c5cf3690a681551162c15d34d935308c8d7#n2857)
and is called when the file operations table does not provide a compat_ioctl
function and no handler is found. usbfs indeed does not provide this, thus
after failing to find a handler it prints this error and as you can see right
after returns EINVAL.
Ah yes I see now, and there is a big honking list of compatible ioctls (so
which are compat without
needing translation from 32 <-> 64 bit) higher up in the file. Which of course
does no contain
the new ioctls. So now we have a different return code when running in native
32 bit versus
when running 32 bits code under a 64 bit kernel how nice (not).
Ok, so treating EINVAL as ENOTTY is going to be the only solution then, can you
try the
attached patch?
Thanks & Regards,
Hans
>From 18d6da51580f8910223833815c3f8b1bef8d32bf Mon Sep 17 00:00:00 2001
From: Hans de Goede <hdego...@redhat.com>
Date: Tue, 11 Mar 2014 18:43:13 +0100
Subject: [PATCH] linux_usbfs: Treat EINVAL as ENOTTY in cases where we may get
ENOTTY
Older 64 bit kernels will return EINVAL to 32 bits userspace for unknown
ioctls. So in places where we check for ENOTTY also check for EINVAL, and
use the fallback path for EINVAL too.
Note that if there really is an invalid parameter in the
detach_kernel_driver_and_claim case, then the fallback path will detect and
report this.
Signed-off-by: Hans de Goede <hdego...@redhat.com>
---
libusb/os/linux_usbfs.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)
diff --git a/libusb/os/linux_usbfs.c b/libusb/os/linux_usbfs.c
index 8962aba..00c8090 100644
--- a/libusb/os/linux_usbfs.c
+++ b/libusb/os/linux_usbfs.c
@@ -1285,7 +1285,8 @@ static int op_open(struct libusb_device_handle *handle)
r = ioctl(hpriv->fd, IOCTL_USBFS_GET_CAPABILITIES, &hpriv->caps);
if (r < 0) {
- if (errno == ENOTTY)
+ /* Older 64 bit kernels return EINVAL to 32 bit apps */
+ if (errno == ENOTTY || errno == EINVAL)
usbi_dbg("getcap not available");
else
usbi_err(HANDLE_CTX(handle), "getcap failed (%d)", errno);
@@ -1631,15 +1632,13 @@ static int detach_kernel_driver_and_claim(struct libusb_device_handle *handle,
strcpy(dc.driver, "usbfs");
dc.flags = USBFS_DISCONNECT_CLAIM_EXCEPT_DRIVER;
r = ioctl(fd, IOCTL_USBFS_DISCONNECT_CLAIM, &dc);
- if (r == 0 || (r != 0 && errno != ENOTTY)) {
- if (r == 0)
- return 0;
-
+ if (r == 0)
+ return 0;
+ /* Older 64 bit kernels return EINVAL to 32 bit apps */
+ if (errno != ENOTTY && errno != EINVAL) {
switch (errno) {
case EBUSY:
return LIBUSB_ERROR_BUSY;
- case EINVAL:
- return LIBUSB_ERROR_INVALID_PARAM;
case ENODEV:
return LIBUSB_ERROR_NO_DEVICE;
}
--
1.8.4.2
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