libftdi Archives

Subject: Re: [bug+possible patch] open device fails in c++ bindings

From: Thomas Jarosch <thomas.jarosch@xxxxxxxxxxxxx>
To: libftdi@xxxxxxxxxxxxxxxxxxxxxxx
Cc: Denis Sirotkin <reg.libftdi@xxxxxxxxxx>
Date: Fri, 16 May 2014 17:42:25 +0200
Hi Denis,

On Thursday, 15. May 2014 15:25:26 Denis Sirotkin wrote:
> I suppose that this is because there is call get_strings_and_reopen()
> which calls ftdi_usb_get_strings() which calls libusb_open() for already
> opened device. A solution may be to call ftdi_usb_close_internal() from
> ftdi_usb_get_strings() function before reopen it or to check if it is
> already opened and don't open twice. I tried both but prefer second and
> simple do like this:
> 
> --- libftdi1-1.1/src/ftdi.c.orig 2014-02-05 22:24:11.000000000 +0600
> +++ libftdi1-1.1/src/ftdi.c      2014-05-15 14:42:13.534444380 +0600
> @@ -413,8 +413,9 @@
>      if ((ftdi==NULL) || (dev==NULL))
>          return -1;
> 
> -    if (libusb_open(dev, &ftdi->usb_dev) < 0)
> -        ftdi_error_return(-4, "libusb_open() failed");
> +    if (ftdi->usb_dev == NULL)
> +        if (libusb_open(dev, &ftdi->usb_dev) < 0)
> +            ftdi_error_return(-4, "libusb_open() failed");
> 
>      if (libusb_get_device_descriptor(dev, &desc) < 0)
>          ftdi_error_return(-11, "libusb_get_device_descriptor() failed");

I've commited an almost identical fix on your behalf. Thanks!

It's quite a "brain puzzle" to follow the call stack from all the layers, 
but your solution looks correct to me :)

Cheers,
Thomas


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