From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752815AbdHGJZN (ORCPT ); Mon, 7 Aug 2017 05:25:13 -0400 Received: from mail-wm0-f54.google.com ([74.125.82.54]:36586 "EHLO mail-wm0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752611AbdHGJZL (ORCPT ); Mon, 7 Aug 2017 05:25:11 -0400 Date: Mon, 7 Aug 2017 11:25:07 +0200 From: Daniel Vetter To: Noralf =?iso-8859-1?Q?Tr=F8nnes?= Cc: Ilia Mirkin , Eric Anholt , Daniel Vetter , Thierry Reding , "linux-kernel@vger.kernel.org" , "dri-devel@lists.freedesktop.org" , Laurent Pinchart Subject: Re: [PATCH v5 2/6] drm/bridge: Add a devm_ allocator for panel bridge. Message-ID: <20170807092507.b735ribfpjm6oejk@phenom.ffwll.local> Mail-Followup-To: Noralf =?iso-8859-1?Q?Tr=F8nnes?= , Ilia Mirkin , Eric Anholt , Daniel Vetter , Thierry Reding , "linux-kernel@vger.kernel.org" , "dri-devel@lists.freedesktop.org" , Laurent Pinchart References: <20170718210510.12229-1-eric@anholt.net> <20170718210510.12229-2-eric@anholt.net> <2023170.2CE3xBA9bq@avalon> <87zibfqd1u.fsf@eliezer.anholt.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Operating-System: Linux phenom 4.11.0-2-amd64 User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Aug 05, 2017 at 12:59:07PM +0200, Noralf Trønnes wrote: > (I had to switch to Daniel's Intel address to get this sent) > > Den 05.08.2017 00.19, skrev Ilia Mirkin: > > On Fri, Aug 4, 2017 at 4:43 PM, Eric Anholt wrote: > > > Laurent Pinchart writes: > > > > > > > Hi Eric, > > > > > > > > (CC'ing Daniel) > > > > > > > > Thank you for the patch. > > > > > > > > On Tuesday 18 Jul 2017 14:05:06 Eric Anholt wrote: > > > > > This will let drivers reduce the error cleanup they need, in > > > > > particular the "is_panel_bridge" flag. > > > > > > > > > > v2: Slight cleanup of remove function by Andrzej > > > > I just want to point out that, in the context of Daniel's work on hot-unplug, > > > > 90% of the devm_* allocations are wrong and will get in the way. All DRM core > > > > objects that are accessible one way or another from userspace will need to be > > > > properly reference-counted and freed only when the last reference disappears, > > > > which could be well after the corresponding device is removed. I believe this > > > > could be one such objects :-/ > > > Sure, if you're hotplugging, your life is pain. For non-hotpluggable > > > devices, like our SOC platform devices (current panel-bridge consumers), > > > this still seems like an excellent simplification of memory management. > > At that point you may as well make your module non-unloadable, and > > return failure when trying to remove a device from management by the > > driver (whatever the opposite of "probe" is, I forget). Hotplugging > > doesn't only happen when physically removing, it can happen for all > > kinds of reasons... and userspace may still hold references in some of > > those cases. > > If drm_open() gets a ref on dev->dev and puts it in drm_release(), > won't that delay devm_* cleanup until userspace is done? No. drm_device is the thing that is refcounted for userspace references like open FD (we're not perfect about it, e.g. sysfs and dma-buf/fence don't). devm_ otoh is tied to the lifetime of the underlying device, and that one can get outlived by drm_device. Or at least afaiui, devm_ stuff is nuked on unplug, and not when the final sw reference of the struct device disappears. Not sure tough, it's complicated. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Vetter Subject: Re: [PATCH v5 2/6] drm/bridge: Add a devm_ allocator for panel bridge. Date: Mon, 7 Aug 2017 11:25:07 +0200 Message-ID: <20170807092507.b735ribfpjm6oejk@phenom.ffwll.local> References: <20170718210510.12229-1-eric@anholt.net> <20170718210510.12229-2-eric@anholt.net> <2023170.2CE3xBA9bq@avalon> <87zibfqd1u.fsf@eliezer.anholt.net> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: Received: from mail-wm0-x231.google.com (mail-wm0-x231.google.com [IPv6:2a00:1450:400c:c09::231]) by gabe.freedesktop.org (Postfix) with ESMTPS id B506A6E3B4 for ; Mon, 7 Aug 2017 09:25:11 +0000 (UTC) Received: by mail-wm0-x231.google.com with SMTP id m85so2387225wma.0 for ; Mon, 07 Aug 2017 02:25:11 -0700 (PDT) Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To: Noralf =?iso-8859-1?Q?Tr=F8nnes?= Cc: "linux-kernel@vger.kernel.org" , "dri-devel@lists.freedesktop.org" , Thierry Reding , Laurent Pinchart , Daniel Vetter List-Id: dri-devel@lists.freedesktop.org T24gU2F0LCBBdWcgMDUsIDIwMTcgYXQgMTI6NTk6MDdQTSArMDIwMCwgTm9yYWxmIFRyw7hubmVz IHdyb3RlOgo+IChJIGhhZCB0byBzd2l0Y2ggdG8gRGFuaWVsJ3MgSW50ZWwgYWRkcmVzcyB0byBn ZXQgdGhpcyBzZW50KQo+IAo+IERlbiAwNS4wOC4yMDE3IDAwLjE5LCBza3JldiBJbGlhIE1pcmtp bjoKPiA+IE9uIEZyaSwgQXVnIDQsIDIwMTcgYXQgNDo0MyBQTSwgRXJpYyBBbmhvbHQgPGVyaWNA YW5ob2x0Lm5ldD4gd3JvdGU6Cj4gPiA+IExhdXJlbnQgUGluY2hhcnQgPGxhdXJlbnQucGluY2hh cnRAaWRlYXNvbmJvYXJkLmNvbT4gd3JpdGVzOgo+ID4gPiAKPiA+ID4gPiBIaSBFcmljLAo+ID4g PiA+IAo+ID4gPiA+IChDQydpbmcgRGFuaWVsKQo+ID4gPiA+IAo+ID4gPiA+IFRoYW5rIHlvdSBm b3IgdGhlIHBhdGNoLgo+ID4gPiA+IAo+ID4gPiA+IE9uIFR1ZXNkYXkgMTggSnVsIDIwMTcgMTQ6 MDU6MDYgRXJpYyBBbmhvbHQgd3JvdGU6Cj4gPiA+ID4gPiBUaGlzIHdpbGwgbGV0IGRyaXZlcnMg cmVkdWNlIHRoZSBlcnJvciBjbGVhbnVwIHRoZXkgbmVlZCwgaW4KPiA+ID4gPiA+IHBhcnRpY3Vs YXIgdGhlICJpc19wYW5lbF9icmlkZ2UiIGZsYWcuCj4gPiA+ID4gPiAKPiA+ID4gPiA+IHYyOiBT bGlnaHQgY2xlYW51cCBvZiByZW1vdmUgZnVuY3Rpb24gYnkgQW5kcnplago+ID4gPiA+IEkganVz dCB3YW50IHRvIHBvaW50IG91dCB0aGF0LCBpbiB0aGUgY29udGV4dCBvZiBEYW5pZWwncyB3b3Jr IG9uIGhvdC11bnBsdWcsCj4gPiA+ID4gOTAlIG9mIHRoZSBkZXZtXyogYWxsb2NhdGlvbnMgYXJl IHdyb25nIGFuZCB3aWxsIGdldCBpbiB0aGUgd2F5LiBBbGwgRFJNIGNvcmUKPiA+ID4gPiBvYmpl Y3RzIHRoYXQgYXJlIGFjY2Vzc2libGUgb25lIHdheSBvciBhbm90aGVyIGZyb20gdXNlcnNwYWNl IHdpbGwgbmVlZCB0byBiZQo+ID4gPiA+IHByb3Blcmx5IHJlZmVyZW5jZS1jb3VudGVkIGFuZCBm cmVlZCBvbmx5IHdoZW4gdGhlIGxhc3QgcmVmZXJlbmNlIGRpc2FwcGVhcnMsCj4gPiA+ID4gd2hp Y2ggY291bGQgYmUgd2VsbCBhZnRlciB0aGUgY29ycmVzcG9uZGluZyBkZXZpY2UgaXMgcmVtb3Zl ZC4gSSBiZWxpZXZlIHRoaXMKPiA+ID4gPiBjb3VsZCBiZSBvbmUgc3VjaCBvYmplY3RzIDotLwo+ ID4gPiBTdXJlLCBpZiB5b3UncmUgaG90cGx1Z2dpbmcsIHlvdXIgbGlmZSBpcyBwYWluLiAgRm9y IG5vbi1ob3RwbHVnZ2FibGUKPiA+ID4gZGV2aWNlcywgbGlrZSBvdXIgU09DIHBsYXRmb3JtIGRl dmljZXMgKGN1cnJlbnQgcGFuZWwtYnJpZGdlIGNvbnN1bWVycyksCj4gPiA+IHRoaXMgc3RpbGwg c2VlbXMgbGlrZSBhbiBleGNlbGxlbnQgc2ltcGxpZmljYXRpb24gb2YgbWVtb3J5IG1hbmFnZW1l bnQuCj4gPiBBdCB0aGF0IHBvaW50IHlvdSBtYXkgYXMgd2VsbCBtYWtlIHlvdXIgbW9kdWxlIG5v bi11bmxvYWRhYmxlLCBhbmQKPiA+IHJldHVybiBmYWlsdXJlIHdoZW4gdHJ5aW5nIHRvIHJlbW92 ZSBhIGRldmljZSBmcm9tIG1hbmFnZW1lbnQgYnkgdGhlCj4gPiBkcml2ZXIgKHdoYXRldmVyIHRo ZSBvcHBvc2l0ZSBvZiAicHJvYmUiIGlzLCBJIGZvcmdldCkuIEhvdHBsdWdnaW5nCj4gPiBkb2Vz bid0IG9ubHkgaGFwcGVuIHdoZW4gcGh5c2ljYWxseSByZW1vdmluZywgaXQgY2FuIGhhcHBlbiBm b3IgYWxsCj4gPiBraW5kcyBvZiByZWFzb25zLi4uIGFuZCB1c2Vyc3BhY2UgbWF5IHN0aWxsIGhv bGQgcmVmZXJlbmNlcyBpbiBzb21lIG9mCj4gPiB0aG9zZSBjYXNlcy4KPiAKPiBJZiBkcm1fb3Bl bigpIGdldHMgYSByZWYgb24gZGV2LT5kZXYgYW5kIHB1dHMgaXQgaW4gZHJtX3JlbGVhc2UoKSwK PiB3b24ndCB0aGF0IGRlbGF5IGRldm1fKiBjbGVhbnVwIHVudGlsIHVzZXJzcGFjZSBpcyBkb25l PwoKTm8uIGRybV9kZXZpY2UgaXMgdGhlIHRoaW5nIHRoYXQgaXMgcmVmY291bnRlZCBmb3IgdXNl cnNwYWNlIHJlZmVyZW5jZXMKbGlrZSBvcGVuIEZEICh3ZSdyZSBub3QgcGVyZmVjdCBhYm91dCBp dCwgZS5nLiBzeXNmcyBhbmQgZG1hLWJ1Zi9mZW5jZQpkb24ndCkuCgpkZXZtXyBvdG9oIGlzIHRp ZWQgdG8gdGhlIGxpZmV0aW1lIG9mIHRoZSB1bmRlcmx5aW5nIGRldmljZSwgYW5kIHRoYXQgb25l CmNhbiBnZXQgb3V0bGl2ZWQgYnkgZHJtX2RldmljZS4gT3IgYXQgbGVhc3QgYWZhaXVpLCBkZXZt XyBzdHVmZiBpcyBudWtlZApvbiB1bnBsdWcsIGFuZCBub3Qgd2hlbiB0aGUgZmluYWwgc3cgcmVm ZXJlbmNlIG9mIHRoZSBzdHJ1Y3QgZGV2aWNlCmRpc2FwcGVhcnMuCgpOb3Qgc3VyZSB0b3VnaCwg aXQncyBjb21wbGljYXRlZC4KLURhbmllbAotLSAKRGFuaWVsIFZldHRlcgpTb2Z0d2FyZSBFbmdp bmVlciwgSW50ZWwgQ29ycG9yYXRpb24KaHR0cDovL2Jsb2cuZmZ3bGwuY2gKX19fX19fX19fX19f X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KZHJpLWRldmVsIG1haWxpbmcgbGlz dApkcmktZGV2ZWxAbGlzdHMuZnJlZWRlc2t0b3Aub3JnCmh0dHBzOi8vbGlzdHMuZnJlZWRlc2t0 b3Aub3JnL21haWxtYW4vbGlzdGluZm8vZHJpLWRldmVsCg==