From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751806AbaK1RH2 (ORCPT ); Fri, 28 Nov 2014 12:07:28 -0500 Received: from mail-wg0-f41.google.com ([74.125.82.41]:58836 "EHLO mail-wg0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751606AbaK1RHX convert rfc822-to-8bit (ORCPT ); Fri, 28 Nov 2014 12:07:23 -0500 MIME-Version: 1.0 In-Reply-To: <4838705.gmGJIAUqrM@avalon> References: <1417044344-20611-1-git-send-email-prabhakar.csengg@gmail.com> <4838705.gmGJIAUqrM@avalon> From: Prabhakar Lad Date: Fri, 28 Nov 2014 17:06:52 +0000 Message-ID: Subject: Re: [PATCH v3] media: usb: uvc: use vb2_ops_wait_prepare/finish helper To: Laurent Pinchart Cc: LMML , LKML , Hans Verkuil Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Laurent, Thanks for the review. On Thu, Nov 27, 2014 at 9:32 PM, Laurent Pinchart wrote: > Hi Prabhakar, [Snip] >> >> + queue->queue.lock = &queue->mutex; > > I'm a bit concerned that this would introduce future breakages. Setting the > queue.lock pointer enables locking in all vb2_fop_* and vb2_ops_wait_* > functions. The uvcvideo driver isn't ready for that, but doesn't use the > vb2_fop_* functions yet, so that's not an issue. However, in the future, > videobuf2 might use the lock in more places, including functions used by the > uvcvideo driver. This could then cause breakages. > Even if in future if videobuf2 uses this lock it would be in helpers mostly, so any way it doesn’t harm :) > It would be better to completely convert the uvcvideo driver to the vb2_fop_* > functions if we want to use vb2_ops_*. I'm not sure how complex that would be > though, and whether it would be possible while still keeping the fine-grained > locking implemented by the uvcvideo driver. Do you think it should be > attempted ? > mmap & poll should be fairly simple, looks like open & release cannot be dropped as it does some usb_autopm_get/put_interface() calls which I am not aware of. Thanks, --Prabhakar Lad >> ret = vb2_queue_init(&queue->queue); >> if (ret) >> return ret; > > -- > Regards, > > Laurent Pinchart >