Alan Stern wrote:
On Wed, 12 Dec 2007, Phil Endecott wrote:
I have a
camera (07b4:0102 Olympus Optical Co., Ltd Camedia E-10/C-220/C-50
Camera) which doesn't like getting a second set_configuration() call
without first getting a reset.
I think that my solution for the time being will be to first test
whether the configuration that I want to use is the same as the one
that the kernel has chosen (which I think I can find via sysfs; it's
not possible via usbdevice_fs is it?),
Sort of. You can send a Get-Configuration request directly to the
device and see what it says.
Hmmm, and hope that they have implemented that request correctly....
I presume that reading /sys/bConfigurationValue just returns the
kernel's record of which configuration was most recently set, rather
than actually doing a get_configuration on the bus - doesn't it?
There is no ioctl to retrieve the value
directly. Using sysfs might be easier.
and only call
ioctl(USBDEVFS_SETCONFIGURATION) if it differs.
I'm now doing this and it at least gets past this particular quirk.
One thing to watch out for is that the USBDEVFS_SETCONFIGURATION call
will fail if any interface is bound to a driver.
I disconnect the kernel drivers on all interfaces before calling
USBDEVFS_SETCONFIGURATION, and it seems to work.
Writing to the sysfs
bConfigurationValue file doesn't have this requirement.
Ah, I didn't know that that was writeable. Interesting. Maybe there
is more that I can achieve by writing to sysfs. I'll have to think
about that. Oh and BTW, there is also a sysfs file just called
'configuration'; what does that do?
Anyway, I'm sending this message as a "heads up" that this issue
exists; I understand that there is a new replacement for usbdevice_fs
in the works, and if it could do anything to sidestep the problem, that
would be useful.
The real problem here is the camera's failure to respond to a second
Set-Config command.
Yes.
I don't see how anything we do can fix that.
Well, if the core didn't do a set_configuration until after the device
had been claimed by a driver (kernel or user-space) then only one
set_configuration would happen. Of course drivers claim interfaces,
not devices....
Regards,
Phil.
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