-------- Original-Nachricht --------
> Datum: Tue, 05 Feb 2013 15:28:03 +0100
> Von: Thomas Jarosch <thomas.jarosch@xxxxxxxxxxxxx>
> An: libftdi@xxxxxxxxxxxxxxxxxxxxxxx
> Betreff: Re: Re: patch to libftdi-1.0 git head, fix opening of multiple
> devices
> Hi Rolf,
>
> On Thursday, 17. January 2013 22:49:53 derRolf@xxxxxxxxxxxxxx wrote:
> > thanks for your thoughts. Yes, we have our own VID/PID. However, our
> > software needs to operate multiple devices with the same VID/PID
> > (multi-threaded). The only difference between the devices is the serial
> > number, which is unique for each device. We have settings and
> > configuration data for the devices, which applies to the specific device
> > (i.e. serial number). Depending on the serial number (i.e. device type)
> > we boot different FPGA bitstreams.
> >
> > Actually I don't think any application could be broken by the patch. If
> > the device is not found, the code still returns the error. It's just
> > that right now the search for the device ends if another device that
> > comes first in the list has already been opened. From my point of view
> > this is a bug (but one that only happens if you play with multiple
> > devices from the same process).
> >
> > I understand that you don't want to apply any changes before the 1.0
> > release. That's fine, I don't use the release code but the git head. But
> > it would be good if the patch could be applied after the release is out.
> > Right now we have patched our git clone and are merging on each pull
> > from upstream.
>
> I've taken a close look at the code in ftdi_usb_open_desc_index().
> If I apply your patch in the current form, the -8 and -9 error code
> will stop to work.
>
> This can be a problem if there's a permission issue reading
> the string descriptors, the function will always return
> -3: "device not found" instead of -8 or -9.
>
> How about using ftdi_usb_find_all() to get a list of all your devices.
> Then you can try to get the strings via ftdi_usb_get_strings()
> and if you f.e. get a serial the device is not in use.
>
> Would that work?
>
> Otherwise we need to come up with a different solution.
>
> Thomas
Thanks again Thomas for this proposal.
I changed
i=ftdi_usb_open_desc(device->ft_handle, 0x0403, 0xefa0, NULL, device_name);
to
if ((ret=ftdi_usb_find_all(device->ft_handle,&devlist,0x0403,0xefa0))<0) {
DBG("ftdi_usb_find_all failed: %d (%s)\n", ret,
ftdi_get_error_string(device->ft_handle));
ftdi_free(device->ft_handle);
FREE(device);
return NULL;
}
for (ret=-1, i=0, curdev = devlist; curdev != NULL; i++, curdev = curdev->n$
//printf("Checking device: %d\n", i);
if ((rv = ftdi_usb_get_strings(device->ft_handle, curdev->dev,
manuf, sizeof(manuf),
descr, sizeof(descr),
serial, sizeof(serial))) < 0) {
//DBG("ftdi_usb_get_strings failed: %d (%s)\n", ret, ftdi_get_error$
continue; // try next in list, device may already have been opened
}
if(strlen(serial) >= len) {
DBG("%s: buffer overrun while copying serial (%d>%d)\n",
__FUNCTION__, strlen(serial), len);
continue; // maybe more luck with next in list?
}
if(!strcmp(serial, device_name)) {
i=ftdi_usb_open_dev(device->ft_handle, curdev->dev);
if (i<0 && i!=-5) {
DBG("ftdi_usb_open_desc failed with code %d for %s\n", i, devic$
ftdi_free(device->ft_handle);
FREE(device);
return NULL;
}
break;
}
}
and can now open devices by serial number if they all have the same PID and
VID. However, I still believe that ftdi_open_by_desc is broken if it does not
allow me to do that when I have already other devices with the same PID/VID
open. Also it is not ideal to require lib users to write that much code just to
open a device.
For me the issue is solved, since my programme works with an unmodified
libftdi1 now.
Thanks and kind regards,
Rolf
--
libftdi - see http://www.intra2net.com/en/developer/libftdi for details.
To unsubscribe send a mail to libftdi+unsubscribe@xxxxxxxxxxxxxxxxxxxxxxx
|
