From mboxrd@z Thu Jan 1 00:00:00 1970 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: base64 Subject: UAS: fix alignment of scatter/gather segments From: Oliver Neukum Message-Id: <1556545099.20085.14.camel@suse.com> Date: Mon, 29 Apr 2019 15:38:19 +0200 To: David Laight , "gregKH@linuxfoundation.org" , "linux-usb@vger.kernel.org" List-ID: T24gTW8sIDIwMTktMDQtMjkgYXQgMTM6MzEgKzAwMDAsIERhdmlkIExhaWdodCB3cm90ZToKPiBG cm9tOiBPbGl2ZXIgTmV1a3VtCj4gPiAKPiA+ICsJICogVVNCIGhhcyB1bnVzdWFsIHNjYXR0ZXIt Z2F0aGVyIHJlcXVpcmVtZW50czogdGhlIGxlbmd0aCBvZiBlYWNoCj4gPiArCSAqIHNjYXR0ZXJs aXN0IGVsZW1lbnQgZXhjZXB0IHRoZSBsYXN0IG11c3QgYmUgZGl2aXNpYmxlIGJ5IHRoZQo+ID4g KwkgKiBCdWxrIG1heHBhY2tldCB2YWx1ZS4gIEZvcnR1bmF0ZWx5IHRoaXMgdmFsdWUgaXMgYWx3 YXlzIGEKPiA+ICsJICogcG93ZXIgb2YgMi4gIEluZm9ybSB0aGUgYmxvY2sgbGF5ZXIgYWJvdXQg dGhpcyByZXF1aXJlbWVudC4KPiA+ICsJICovCj4gCj4gVGhhdCBpc24ndCB0aGUgY29ycmVjdCBy ZXN0cmljdGlvbiBmb3IgWEhDSS4KPiBJdCBoYXMgaXRzIG93biBwZXJ2ZXJzZSByZXN0cmljdGlv bnMuCj4gSSB0aGluayB0aGV5IGFyZSBhbGwgaGFuZGxlZCB3aXRoaW4gdGhlIHhoY2kgZHJpdmVy LgoKWWVzLCBidXQgdGhhdCBkb2VzIG5vdCBtYXR0ZXIuIFlvdSBqdXN0IGNhbm5vdCBhc3N1bWUg dGhhdCBvbmx5ClhIQ0kgd2lsbCBiZSB1c2VkIHdpdGggVUFTLiBJbiBwYXJ0aWN1bGFyIHZpcnR1 YWwgZHJpdmVycyB3aWxsCmJlIHVzZWQuCgoJUmVnYXJkcwoJCU9saXZlcgo= From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 67E4AC43219 for ; Mon, 29 Apr 2019 13:38:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3F5A520652 for ; Mon, 29 Apr 2019 13:38:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727555AbfD2Nic (ORCPT ); Mon, 29 Apr 2019 09:38:32 -0400 Received: from mx2.suse.de ([195.135.220.15]:40644 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725838AbfD2Nic (ORCPT ); Mon, 29 Apr 2019 09:38:32 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 6AA89ABA1; Mon, 29 Apr 2019 13:38:31 +0000 (UTC) Message-ID: <1556545099.20085.14.camel@suse.com> Subject: Re: [PATCH] UAS: fix alignment of scatter/gather segments From: Oliver Neukum To: David Laight , "gregKH@linuxfoundation.org" , "linux-usb@vger.kernel.org" Date: Mon, 29 Apr 2019 15:38:19 +0200 In-Reply-To: References: <20190429122026.4249-1-oneukum@suse.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.26.6 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org Message-ID: <20190429133819.D9lsLWMfXX5ALEHwBloeEODiJ1ewQCsjXz4STjYovXM@z> On Mo, 2019-04-29 at 13:31 +0000, David Laight wrote: > From: Oliver Neukum > > > > + * USB has unusual scatter-gather requirements: the length of each > > + * scatterlist element except the last must be divisible by the > > + * Bulk maxpacket value. Fortunately this value is always a > > + * power of 2. Inform the block layer about this requirement. > > + */ > > That isn't the correct restriction for XHCI. > It has its own perverse restrictions. > I think they are all handled within the xhci driver. Yes, but that does not matter. You just cannot assume that only XHCI will be used with UAS. In particular virtual drivers will be used. Regards Oliver