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Date:   Tue, 11 Jun 2019 09:50:40 -0400 (EDT)
From:   Alan Stern <stern@rowland.harvard.edu>
To:     Dmitry Torokhov <dmitry.torokhov@gmail.com>
cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        <bleung@chromium.org>, <linux-usb@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>,
        <libusb-devel@lists.sourceforge.net>
Subject: Re: [PATCH] USB: add usbfs ioctl to retrieve the connection parameters
In-Reply-To: <20190610223658.GA162167@dtor-ws>
Message-ID: <Pine.LNX.4.44L0.1906110950130.1535-100000@iolanthe.rowland.org>
MIME-Version: 1.0
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Sender: linux-kernel-owner@vger.kernel.org
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On Mon, 10 Jun 2019, Dmitry Torokhov wrote:

> Recently usfbs gained availability to retrieve device speed, but there
> is sill no way to determine the bus number or list of ports the device
> is connected to when using usbfs. While this information can be obtained
> from sysfs, not all environments allow sysfs access. In a jailed
> environment a program might be simply given an opened file descriptor to
> usbfs device, and it is really important that all data can be gathered
> from said file descriptor.
> 
> This patch introduces a new ioctl, USBDEVFS_CONNINFO_EX, which return
> extended connection information for the device, including the bus
> number, address, port list and speed. The API allows kernel to extend
> amount of data returned by the ioctl and userspace has an option of
> adjusting the amount of data it is willing to consume. A new capability,
> USBDEVFS_CAP_CONNINFO_EX, is introduced to help userspace in determining
> whether the kernel supports this new ioctl.
> 
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Acked-by: Alan Stern <stern@rowland.harvard.edu>