linux-kernel - Re: [PATCH v6 36/42] drm/mediatek: mtk_hdmi

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Message-ID: <e94e5f788baf00cde94c8c3fd9065804de6d4d1e.camel@mediatek.com>
Date: Thu, 13 Feb 2025 09:01:44 +0000
From: CK Hu (胡俊光) <ck.hu@...iatek.com>
To: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	"chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>
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	<junzhi.zhao@...iatek.com>
Subject: Re: [PATCH v6 36/42] drm/mediatek: mtk_hdmi_common: Make CEC support
 optional

On Tue, 2025-02-11 at 12:34 +0100, AngeloGioacchino Del Regno wrote:
> External email : Please do not click links or open attachments until you have verified the sender or the content.
> 
> 
> 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.
> 
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...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 3dfde63198e5..5ea45608921c 100644
> --- a/drivers/gpu/drm/mediatek/mtk_hdmi_common.c
> +++ b/drivers/gpu/drm/mediatek/mtk_hdmi_common.c
> @@ -254,12 +254,11 @@ 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");
> 
>         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;
>         }
> @@ -323,7 +322,9 @@ 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");

You change v1 behavior here.
When there is no CEC in device tree, original v1 would return -EINVAL.
But now, v1 return 0.

In mtk_hdmi_probe() of previous patch, you add checking of hdmi->cec_dev.
I think that checking is related to this, so I would like that checking to be in this patch because that checking is strongly related to this patch.

After this modification,

Reviewed-by: CK Hu <ck.hu@...iatek.com>

> +       else if (ret)
>                 return ret;
> 
>         return 0;
> --
> 2.48.1
>