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Improve the userspace USB string reading function in LibUSB.

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Some USB devices does not allow a partial descriptor readout.

Found by:		bz @
MFC after:		1 week
Sponsored by:		Mellanox Technologies
This commit is contained in:
Hans Petter Selasky 2018-06-26 16:00:16 +00:00
parent 8518997526
commit dfd30b26a9
1 changed files with 12 additions and 9 deletions
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21
lib/libusb/libusb20.c
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@ -814,6 +814,7 @@ libusb20_dev_req_string_sync(struct libusb20_device *pdev,
{
struct LIBUSB20_CONTROL_SETUP_DECODED req;
int error;
int flags;
/* make sure memory is initialised */
memset(ptr, 0, len);
@ -840,22 +841,24 @@ libusb20_dev_req_string_sync(struct libusb20_device *pdev,
error = libusb20_dev_request_sync(pdev, &req,
ptr, NULL, 1000, LIBUSB20_TRANSFER_SINGLE_SHORT_NOT_OK);
if (error) {
return (error);
/* try to request full string */
req.wLength = 255;
flags = 0;
} else {
/* extract length and request full string */
req.wLength = *(uint8_t *)ptr;
flags = LIBUSB20_TRANSFER_SINGLE_SHORT_NOT_OK;
}
req.wLength = *(uint8_t *)ptr; /* bytes */
if (req.wLength > len) {
/* partial string read */
req.wLength = len;
}
error = libusb20_dev_request_sync(pdev, &req,
ptr, NULL, 1000, LIBUSB20_TRANSFER_SINGLE_SHORT_NOT_OK);
if (error) {
error = libusb20_dev_request_sync(pdev, &req, ptr, NULL, 1000, flags);
if (error)
return (error);
}
if (((uint8_t *)ptr)[1] != LIBUSB20_DT_STRING) {
if (((uint8_t *)ptr)[1] != LIBUSB20_DT_STRING)
return (LIBUSB20_ERROR_OTHER);
}
return (0); /* success */
}