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jtag/drivers/libusb1_common: avoid device reset when reselecting configuration 

According to [1], we shouldn't reselect an already active configuration to avoid needless device reset. This is known to cause issues with e.g. LPC Link2 with JLink firmware.

[1] http://libusb.sourceforge.net/api-1.0/caveats.html#configsel

Change-Id: I3568ada77780a521548c450090db7173f8d0b2dd
Signed-off-by: Paul Fertser <fercerpav@gmail.com>
Signed-off-by: Anders Oleson <anders@openpuma.org>
Reviewed-on: http://openocd.zylin.com/2288
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>
This commit is contained in:
Anders 2014-10-01 19:42:33 -07:00 committed by Spencer Oliver
parent 48a681c741
commit ca8f8e7e77
1 changed files with 14 additions and 2 deletions
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14
src/jtag/drivers/libusb1_common.c
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@ -165,8 +165,20 @@ int jtag_libusb_set_configuration(jtag_libusb_device_handle *devh,
int retCode = -99;
struct libusb_config_descriptor *config = NULL;
int current_config = -1;
libusb_get_config_descriptor(udev, configuration, &config);
retCode = libusb_get_configuration(devh, &current_config);
if (retCode != 0)
return retCode;
retCode = libusb_get_config_descriptor(udev, configuration, &config);
if (retCode != 0 || config == NULL)
return retCode;
/* Only change the configuration if it is not already set to the
same one. Otherwise this issues a lightweight reset and hangs
LPC-Link2 with JLink firmware. */
if (current_config != config->bConfigurationValue)
retCode = libusb_set_configuration(devh, config->bConfigurationValue);
libusb_free_config_descriptor(config);