From mboxrd@z Thu Jan 1 00:00:00 1970 From: Juergen Gross Subject: Re: [PATCH V6 3/7] libxl: add pvusb API Date: Fri, 11 Sep 2015 15:55:50 +0200 Message-ID: <55F2DD66.1040507@suse.com> References: <1439202928-24813-1-git-send-email-cyliu@suse.com> <1439202928-24813-4-git-send-email-cyliu@suse.com> <1441721852.24450.120.camel@citrix.com> <55F2F64F02000066000508CA@relay2.provo.novell.com> <1441978018.3549.33.camel@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1441978018.3549.33.camel@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Campbell , Chun Yan Liu , xen-devel@lists.xen.org Cc: george.dunlap@eu.citrix.com, Ian.Jackson@eu.citrix.com, Jim Fehlig , Simon Cao , wei.liu2@citrix.com List-Id: xen-devel@lists.xenproject.org On 09/11/2015 03:26 PM, Ian Campbell wrote: > On Thu, 2015-09-10 at 23:42 -0600, Chun Yan Liu wrote: >> >>> Do these fields have any particular size requirements arising from e.g. the >>> USB spec or from possible dom0 implementations? >>> >>> If they have a well defined fixed size from a USB spec then maybe we >>> could >>> use the appropriate fixed size types? >> >> Di> dn't see the size limitation. In Linux kernel code, busnum and devnum (here >> 'hostbus, hostaddr') are both 'int' type. > > Is that a Linux-specific implementation detail or a fundamental property of > USB? We should be designing the interface around Linux implementation > details. It seems like something in the USB spec ought to define precisely > the number of bits in both a bus number and a device address within that > bus. The USB spec is only about _the_ bus. How many buses a host can operate and how they are numbered is outside the USB spec. Devices are addressed via their ports in the USB protocol. devnum is a unique index for a device on the bus, the USB protocol equivalent is a list of ports of: - 1 member in case of direct attached devices - multiple members in case of hubs between bus and device > > Note also that integer in the libxl IDL is signed 24 bits. > >> And idProduct and idVendor are 'u16'. > > That's a USB spec thing, I think, so int16 in the IDL seems appropriate. Correct. Juergen