From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from perceval.ideasonboard.com ([95.142.166.194]:57427 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756470Ab2ISSpn (ORCPT ); Wed, 19 Sep 2012 14:45:43 -0400 From: Laurent Pinchart To: Hans Verkuil Cc: linux-media@vger.kernel.org, Hans Verkuil Subject: Re: [RFCv2 API PATCH 05/28] DocBook: bus_info can no longer be empty. Date: Wed, 19 Sep 2012 20:46:19 +0200 Message-ID: <2703771.az7WlvTDGK@avalon> In-Reply-To: <201209131240.07085.hverkuil@xs4all.nl> References: <1347024568-32602-1-git-send-email-hverkuil@xs4all.nl> <2833220.AbcIRhH3Bk@avalon> <201209131240.07085.hverkuil@xs4all.nl> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-media-owner@vger.kernel.org List-ID: Hi Hans, On Thursday 13 September 2012 12:40:07 Hans Verkuil wrote: > On Thu 13 September 2012 03:24:53 Laurent Pinchart wrote: > > On Friday 07 September 2012 15:29:05 Hans Verkuil wrote: > > > From: Hans Verkuil > > > > > > During the 2012 Media Workshop it was decided that bus_info as returned > > > by VIDIOC_QUERYCAP can no longer be empty. It should be a unique > > > identifier, and empty strings are obviously not unique. > > > > > > Signed-off-by: Hans Verkuil > > > --- > > > > > > Documentation/DocBook/media/v4l/vidioc-querycap.xml | 14 > > > ++++++++++---- > > > 1 file changed, 10 insertions(+), 4 deletions(-) > > > > > > diff --git a/Documentation/DocBook/media/v4l/vidioc-querycap.xml > > > b/Documentation/DocBook/media/v4l/vidioc-querycap.xml index > > > f33dd74..d5b1248 100644 > > > --- a/Documentation/DocBook/media/v4l/vidioc-querycap.xml > > > +++ b/Documentation/DocBook/media/v4l/vidioc-querycap.xml > > > @@ -90,11 +90,17 @@ ambiguities. > > > > > > __u8 > > > bus_info[32] > > > Location of the device in the system, a > > > > > > -NUL-terminated ASCII string. For example: "PCI Slot 4". This > > > +NUL-terminated ASCII string. For example: "PCI:0000:05:06.0". This > > > > > > information is intended for users, to distinguish multiple > > > > > > -identical devices. If no such information is available the field may > > > -simply count the devices controlled by the driver, or contain the > > > -empty string (bus_info[0] = 0). > > > +identical devices. If no such information is available the field must > > > +simply count the devices controlled by the driver ("vivi-000"). The > > > bus_info > > > +must start with "PCI:" for PCI boards, "PCIe:" for PCI Express boards, > > > +"usb-" for USB devices, "I2C:" for i2c devices, "ISA:" for ISA devices > > > and > > > +"parport" for parallel port devices. > > > > What about being a bit more precise than that ? We could specify what API > > drivers must use to fill the bus_info field. For instance, for USB > > devices, > > usb_make_path() is currently used by most drivers (which, by the way, > > doesn't return a string that starts with "USB:"). > > I thought about that, but should that be defined in the spec? I'm not sure > if that's the right place. On the other hand, if we don't specify the format of the bus_info field precisely, it will only be usable as an opaque identifier to userspace. What do we want to do with bus_info ? Telling otherwise identical devices apart is a must, but do we want to provide more information to userspace ? If the field had been longer a sysfs path might have been a good idea, but it won't fit. -- Regards, Laurent Pinchart