linux-kernel - Re: [PATCH v11 05/11] drm/mediatek: mtk_hdmi

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CAAOTY_-f89vzGXzb_xRgpmx050tVM2+Ud6afR5iNycTROSmcYw@mail.gmail.com>
Date: Fri, 24 Oct 2025 00:35:29 +0000
From: Chun-Kuang Hu <chunkuang.hu@...nel.org>
To: Louis-Alexis Eyraud <louisalexis.eyraud@...labora.com>
Cc: Chun-Kuang Hu <chunkuang.hu@...nel.org>, Philipp Zabel <p.zabel@...gutronix.de>, 
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
	Matthias Brugger <matthias.bgg@...il.com>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, CK Hu <ck.hu@...iatek.com>, 
	kernel@...labora.com, dri-devel@...ts.freedesktop.org, 
	linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v11 05/11] drm/mediatek: mtk_hdmi_common: Make CEC support optional

Louis-Alexis Eyraud <louisalexis.eyraud@...labora.com> 於 2025年10月23日
週四 下午5:05寫道：
>
> Hi,
>
> On Thu, 2025-10-23 at 15:59 +0000, Chun-Kuang Hu wrote:
> > Hi, Louis:
> >
> > Louis-Alexis Eyraud <louisalexis.eyraud@...labora.com> 於 2025年10月23日
> > 週四 上午10:32寫道：
> > >
> > > From: AngeloGioacchino Del Regno
> > > <angelogioacchino.delregno@...labora.com>
> > >
> > > In preparation for adding a new driver for HDMIv2, for which CEC
> > > is not strictly required, change the of_get_compatible_child()
> > > failure error to -ENOTSUPP to be able to differentiate between
> > > error conditions in mtk_hdmi_dt_parse_pdata().
> > >
> > > In that case, if -ENOTSUPP is returned, this driver will print
> > > an informative message saying that CEC support is unavailable,
> > > as the devicetree node for that was not found, but after that,
> > > function mtk_hdmi_dt_parse_pdata() will not return error to
> > > the caller.
> > >
> > > This will not change functionality of the mtk_hdmi (v1) driver
> > > as that is still checking whether CEC is present and, if not,
> > > will fail probing with an error saying that CEC is required
> > > by HDMIv1.
> > >
> > > Reviewed-by: CK Hu <ck.hu@...iatek.com>
> > > Signed-off-by: AngeloGioacchino Del Regno
> > > <angelogioacchino.delregno@...labora.com>
> > > Signed-off-by: Louis-Alexis Eyraud
> > > <louisalexis.eyraud@...labora.com>
> > > ---
> > >  drivers/gpu/drm/mediatek/mtk_hdmi_common.c | 9 +++++----
> > >  1 file changed, 5 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/mediatek/mtk_hdmi_common.c
> > > b/drivers/gpu/drm/mediatek/mtk_hdmi_common.c
> > > index
> > > f28e63716d7c2e2c6bdf5b28d24789bc926d2beb..989479fdfe40952762a1b6379
> > > 7bf602b520dcac5 100644
> > > --- a/drivers/gpu/drm/mediatek/mtk_hdmi_common.c
> > > +++ b/drivers/gpu/drm/mediatek/mtk_hdmi_common.c
> > > @@ -253,12 +253,11 @@ static int mtk_hdmi_get_cec_dev(struct
> > > mtk_hdmi *hdmi, struct device *dev, struc
> > >         /* The CEC module handles HDMI hotplug detection */
> > >         cec_np = of_get_compatible_child(np->parent,
> > > "mediatek,mt8173-cec");
> > >         if (!cec_np)
> > > -               return dev_err_probe(dev, -EINVAL, "Failed to find
> > > CEC node\n");
> > > +               return dev_err_probe(dev, -ENOTSUPP, "Failed to
> > > find CEC node\n");
> >
> > The checkpatch show the warning:
> >
> > WARNING: ENOTSUPP is not a SUSV4 error code, prefer EOPNOTSUPP
> > #40: FILE: drivers/gpu/drm/mediatek/mtk_hdmi_common.c:256:
> > +        return dev_err_probe(dev, -ENOTSUPP, "Failed to find CEC
> > node\n");
> >
> > I find many driver use ENOTSUPP, so I'm not sure which one is better.
> > I really don't understand the description about these two error code
> > [1].
> > If you choose ENOTSUPP, please give me some explain.
> >
> > [1] https://man7.org/linux/man-pages/man3/errno.3.html
> >
> > Regards,
> > Chun-Kuang.
> >
> >
> I think ENOTSUPP can be replaced by EOPNOTSUPP in this patch safely.
>
> There is only a single call of the mtk_hdmi_get_cec_dev function in the
> driver and the code that checks this particular return code value in
> mtk_hdmi_dt_parse_pdata function is also added by this patch.
>
> I also don't see no other occurrence of ENOTSUPP code in mediatek-drm
> and since checkpatch recommends to prefer EOPNOTSUPP over ENOTSUPP,
> let's replace it in this patch (both code and commit message).
>
> Do you want me to send a new version of the series for this change?

It's not necessary to send a new version of this series.
I would modify this patch when I apply it.

Regards,
Chun-Kuang.

>
> Regards,
> Louis-Alexis
>
> > >         cec_pdev = of_find_device_by_node(cec_np);
> > >         if (!cec_pdev) {
> > > -               dev_err(hdmi->dev, "Waiting for CEC device %pOF\n",
> > > -                       cec_np);
> > > +               dev_err(hdmi->dev, "Waiting for CEC device %pOF\n",
> > > cec_np);
> > >                 of_node_put(cec_np);
> > >                 return -EPROBE_DEFER;
> > >         }
> > > @@ -319,7 +318,9 @@ static int mtk_hdmi_dt_parse_pdata(struct
> > > mtk_hdmi *hdmi, struct platform_device
> > >                 return dev_err_probe(dev, -EINVAL, "Failed to get
> > > ddc i2c adapter by node\n");
> > >
> > >         ret = mtk_hdmi_get_cec_dev(hdmi, dev, np);
> > > -       if (ret)
> > > +       if (ret == -ENOTSUPP)
> > > +               dev_info(dev, "CEC support unavailable: node not
> > > found\n");
> > > +       else if (ret)
> > >                 return ret;
> > >
> > >         return 0;
> > >
> > > --
> > > 2.51.0
> > >