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Date: Tue, 5 Aug 2025 01:43:48 +0000
From: Ming Qian <ming.qian@....com>
To: Jacopo Mondi <jacopo.mondi@...asonboard.com>, Mauro Carvalho Chehab
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Subject: RE: [EXT] [PATCH 14/65] media: amphion: Delete v4l2_fh synchronously
 in .release()



>-----Original Message-----
>From: Jacopo Mondi <jacopo.mondi@...asonboard.com>
>Sent: Saturday, August 2, 2025 5:23 PM
>To: Mauro Carvalho Chehab <mchehab@...nel.org>; Devarsh Thakkar
><devarsht@...com>; Benoit Parrot <bparrot@...com>; Hans Verkuil
><hverkuil@...nel.org>; Mike Isely <isely@...ox.com>; Laurent Pinchart
><laurent.pinchart@...asonboard.com>; Hans de Goede <hansg@...nel.org>;
>Parthiban Veerasooran <parthiban.veerasooran@...rochip.com>; Christian
>Gromm <christian.gromm@...rochip.com>; Greg Kroah-Hartman
><gregkh@...uxfoundation.org>; Alex Shi <alexs@...nel.org>; Yanteng Si
><si.yanteng@...ux.dev>; Dongliang Mu <dzm91@...t.edu.cn>; Jonathan
>Corbet <corbet@....net>; Tomasz Figa <tfiga@...omium.org>; Marek
>Szyprowski <m.szyprowski@...sung.com>; Andy Walls
><awalls@...metrocast.net>; Michael Tretter <m.tretter@...gutronix.de>;
>Pengutronix Kernel Team <kernel@...gutronix.de>; Bin Liu
><bin.liu@...iatek.com>; Matthias Brugger <matthias.bgg@...il.com>;
>AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>;
>Dmitry Osipenko <digetx@...il.com>; Thierry Reding
><thierry.reding@...il.com>; Jonathan Hunter <jonathanh@...dia.com>;
>Mirela Rabulea <mirela.rabulea@....com>; Shawn Guo
><shawnguo@...nel.org>; Sascha Hauer <s.hauer@...gutronix.de>; Fabio
>Estevam <festevam@...il.com>; Kieran Bingham
><kieran.bingham+renesas@...asonboard.com>; Michal Simek
><michal.simek@....com>; Ming Qian <ming.qian@....com>; Eagle Zhou
><eagle.zhou@....com>; Xavier Roumegue (OSS)
><xavier.roumegue@....nxp.com>; Philipp Zabel <p.zabel@...gutronix.de>;
>Vikash Garodia <quic_vgarodia@...cinc.com>; Dikshita Agarwal
><quic_dikshita@...cinc.com>; Abhinav Kumar <abhinav.kumar@...ux.dev>;
>Bryan O'Donoghue <bryan.odonoghue@...aro.org>; Sylwester Nawrocki
><sylvester.nawrocki@...il.com>; Jernej Skrabec <jernej.skrabec@...il.com>;
>Chen-Yu Tsai <wens@...e.org>; Samuel Holland <samuel@...lland.org>;
>Daniel Almeida <daniel.almeida@...labora.com>; Neil Armstrong
><neil.armstrong@...aro.org>; Kevin Hilman <khilman@...libre.com>; Jerome
>Brunet <jbrunet@...libre.com>; Martin Blumenstingl
><martin.blumenstingl@...glemail.com>; Nas Chung
><nas.chung@...psnmedia.com>; Jackson Lee
><jackson.lee@...psnmedia.com>; Minghsiu Tsai
><minghsiu.tsai@...iatek.com>; Houlong Wei <houlong.wei@...iatek.com>;
>Andrew-CT Chen <andrew-ct.chen@...iatek.com>; Tiffany Lin
><tiffany.lin@...iatek.com>; Yunfei Dong <yunfei.dong@...iatek.com>;
>Geert Uytterhoeven <geert+renesas@...der.be>; Magnus Damm
><magnus.damm@...il.com>; Mikhail Ulyanov
><mikhail.ulyanov@...entembedded.com>; Jacob Chen <jacob-
>chen@...wrt.com>; Ezequiel Garcia <ezequiel@...guardiasur.com.ar>; Heiko
>Stuebner <heiko@...ech.de>; Detlev Casanova
><detlev.casanova@...labora.com>; Krzysztof Kozlowski <krzk@...nel.org>;
>Alim Akhtar <alim.akhtar@...sung.com>; Sylwester Nawrocki
><s.nawrocki@...sung.com>; Łukasz Stelmach <l.stelmach@...sung.com>;
>Andrzej Pietrasiewicz <andrzejtp2010@...il.com>; Jacek Anaszewski
><jacek.anaszewski@...il.com>; Andrzej Hajda <andrzej.hajda@...el.com>;
>Fabien Dessenne <fabien.dessenne@...s.st.com>; Hugues Fruchet
><hugues.fruchet@...s.st.com>; Jean-Christophe Trotin <jean-
>christophe.trotin@...s.st.com>; Maxime Coquelin
><mcoquelin.stm32@...il.com>; Alexandre Torgue
><alexandre.torgue@...s.st.com>; Nicolas Dufresne
><nicolas.dufresne@...labora.com>; Benjamin Gaignard
><benjamin.gaignard@...labora.com>; Steve Longerbeam
><slongerbeam@...il.com>; Maxime Ripard <mripard@...nel.org>; Paul
>Kocialkowski <paulk@...-base.io>; Niklas Söderlund
><niklas.soderlund@...natech.se>; Robert Foss <rfoss@...nel.org>; Todor
>Tomov <todor.too@...il.com>; Vladimir Zapolskiy
><vladimir.zapolskiy@...aro.org>; Corentin Labbe <clabbe@...libre.com>;
>Sakari Ailus <sakari.ailus@...ux.intel.com>; Bingbu Cao
><bingbu.cao@...el.com>; Tianshu Qiu <tian.shu.qiu@...el.com>; Stanislaw
>Gruszka <stanislaw.gruszka@...ux.intel.com>
>Cc: linux-media@...r.kernel.org; linux-kernel@...r.kernel.org; linux-
>staging@...ts.linux.dev; linux-doc@...r.kernel.org; linux-arm-
>kernel@...ts.infradead.org; linux-mediatek@...ts.infradead.org; linux-
>tegra@...r.kernel.org; imx@...ts.linux.dev; linux-renesas-soc@...r.kernel.org;
>linux-arm-msm@...r.kernel.org; linux-samsung-soc@...r.kernel.org; linux-
>sunxi@...ts.linux.dev; linux-usb@...r.kernel.org; linux-
>amlogic@...ts.infradead.org; linux-rockchip@...ts.infradead.org; linux-
>stm32@...md-mailman.stormreply.com; mjpeg-users@...ts.sourceforge.net;
>Jacopo Mondi <jacopo.mondi@...asonboard.com>
>Subject: [EXT] [PATCH 14/65] media: amphion: Delete v4l2_fh synchronously
>in .release()
>
>Caution: This is an external email. Please take care when clicking links or
>opening attachments. When in doubt, report the message using the 'Report
>this email' button
>
>
>From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
>
>The v4l2_fh initialized and added in vpu_v4l2_open() is delete and cleaned up
>when the last reference to the vpu_inst is released. This may happen later than
>at vpu_v4l2_close() time.
>
>Not deleting and cleaning up the v4l2_fh when closing the file handle to the
>video device is not ideal, as the v4l2_fh will still be present in the video device's
>fh_list, and will store a copy of events queued to the video device. There may
>also be other side effects of keeping alive an object that represents an open file
>handle after the file handle is closed.
>
>The v4l2_fh instance is embedded in the vpu_inst structure, and is accessed in
>two different ways:
>
>- in vpu_notify_eos() and vpu_notify_source_change(), to queue V4L2
>  events to the file handle ; and
>
>- through the driver to access the v4l2_fh.m2m_ctx pointer.
>
>The v4l2_fh.m2m_ctx pointer is not touched by v4l2_fh_del() and
>v4l2_fh_exit(). It is set to NULL by the driver when closing the file handle, in
>vpu_v4l2_close().
>
>The vpu_notify_eos() and vpu_notify_source_change() functions are called in
>vpu_set_last_buffer_dequeued() and vdec_handle_resolution_change()
>respectively, only if the v4l2_fh.m2m_ctx pointer is not NULL. There is therefore
>a guarantee that no new event will be queued to the v4l2_fh after
>vpu_v4l2_close() destroys the m2m_ctx.
>
>The vpu_notify_eos() function is also called from vpu_vb2_buf_finish(), which
>is guaranteed to be called for all queued buffers when
>vpu_v4l2_close() calls v4l2_m2m_ctx_release(), and will not be called later.
>
>It is therefore safe to assume that the driver will not touch the v4l2_fh, except
>to check the m2m_ctx pointer, after vpu_v4l2_close() destroys the m2m_ctx.
>We can safely delete and cleanup the v4l2_fh synchronously in
>vpu_v4l2_close().
>
>Signed-off-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
>Signed-off-by: Jacopo Mondi <jacopo.mondi@...asonboard.com>

Reviewed-by: Ming Qian <ming.qian@....nxp.com>

>---
> drivers/media/platform/amphion/vpu_v4l2.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
>diff --git a/drivers/media/platform/amphion/vpu_v4l2.c
>b/drivers/media/platform/amphion/vpu_v4l2.c
>index
>306d94e0f8e79faaacfa35b28e5786860f7bd1ca..57ca6262bb04b356a85e217ef
>51cfb13cb9a0a36 100644
>--- a/drivers/media/platform/amphion/vpu_v4l2.c
>+++ b/drivers/media/platform/amphion/vpu_v4l2.c
>@@ -724,8 +724,6 @@ static int vpu_v4l2_release(struct vpu_inst *inst)
>
>        v4l2_ctrl_handler_free(&inst->ctrl_handler);
>        mutex_destroy(&inst->lock);
>-       v4l2_fh_del(&inst->fh);
>-       v4l2_fh_exit(&inst->fh);
>
>        call_void_vop(inst, cleanup);
>
>@@ -794,6 +792,8 @@ int vpu_v4l2_open(struct file *file, struct vpu_inst
>*inst)
>
>        return 0;
> error:
>+       v4l2_fh_del(&inst->fh);
>+       v4l2_fh_exit(&inst->fh);
>        vpu_inst_put(inst);
>        return ret;
> }
>@@ -813,6 +813,9 @@ int vpu_v4l2_close(struct file *file)
>        call_void_vop(inst, release);
>        vpu_inst_unlock(inst);
>
>+       v4l2_fh_del(&inst->fh);
>+       v4l2_fh_exit(&inst->fh);
>+
>        vpu_inst_unregister(inst);
>        vpu_inst_put(inst);
>
>
>--
>2.49.0

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