linux-kernel - Re: [PATCH v2 79/91] drm/vc4: hdmi: Deal with multiple debugfs files

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Date:   Sat, 25 Apr 2020 23:26:31 +0200
From:   Stefan Wahren <stefan.wahren@...e.com>
To:     Maxime Ripard <maxime@...no.tech>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Eric Anholt <eric@...olt.net>
Cc:     Tim Gover <tim.gover@...pberrypi.com>,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        bcm-kernel-feedback-list@...adcom.com,
        linux-rpi-kernel@...ts.infradead.org,
        Phil Elwell <phil@...pberrypi.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 79/91] drm/vc4: hdmi: Deal with multiple debugfs files

Hi Maxime,

Am 24.04.20 um 17:35 schrieb Maxime Ripard:
> The HDMI driver was registering a single debugfs file so far with the name
> hdmi_regs.
>
> Obviously, this is not going to work anymore when will have multiple HDMI
> controllers since we will end up trying to register two files with the same
> name.
>
> Let's use the ID to avoid that name conflict.

even with this patch there is a name conflict in debugfs using Linux
5.7-rc1. Dave Stevenson addressed this by using different card names
[1]. Since this patch won't apply anymore here is my suggestion:

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index 29287ab..7209397 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -1181,9 +1181,14 @@ static int vc4_hdmi_audio_init(struct vc4_hdmi
*vc4_hdmi)
 
     card->dai_link = dai_link;
     card->num_links = 1;
-    card->name = "vc4-hdmi";
     card->dev = dev;
 
+    if (vc4_hdmi->variant->encoder_type == VC4_ENCODER_TYPE_HDMI1) {
+        card->name = "vc4-hdmi1";
+    } else {
+        card->name = "vc4-hdmi";
+    }
+
     /*
      * Be careful, snd_soc_register_card() calls dev_set_drvdata() and
      * stores a pointer to the snd card object in dev->driver_data. This
-- 
2.7.4


[1] -
https://github.com/raspberrypi/linux/pull/3515/commits/82fe6c16811e5acc9bdbbf298db1b30f84b820d2

>
> Signed-off-by: Maxime Ripard <maxime@...no.tech>
> ---
>  drivers/gpu/drm/vc4/vc4_hdmi.c | 5 ++++-
>  drivers/gpu/drm/vc4/vc4_hdmi.h | 3 +++
>  2 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
> index aaf96420d0ec..aae5b10a2d11 100644
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
> @@ -1377,7 +1377,9 @@ static int vc4_hdmi_bind(struct device *dev, struct device *master, void *data)
>  	if (ret)
>  		goto err_destroy_encoder;
>  
> -	vc4_debugfs_add_file(drm, "hdmi_regs", vc4_hdmi_debugfs_regs, vc4_hdmi);
> +	vc4_debugfs_add_file(drm, variant->debugfs_name,
> +			     vc4_hdmi_debugfs_regs,
> +			     vc4_hdmi);
>  
>  	return 0;
>  
> @@ -1439,6 +1441,7 @@ static int vc4_hdmi_dev_remove(struct platform_device *pdev)
>  
>  static const struct vc4_hdmi_variant bcm2835_variant = {
>  	.encoder_type		= VC4_ENCODER_TYPE_HDMI0,
> +	.debugfs_name		= "hdmi_regs",
>  	.registers		= vc4_hdmi_fields,
>  	.num_registers		= ARRAY_SIZE(vc4_hdmi_fields),
>  
> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.h b/drivers/gpu/drm/vc4/vc4_hdmi.h
> index 4240c5ea7fde..22100820c81b 100644
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.h
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.h
> @@ -30,6 +30,9 @@ struct vc4_hdmi_variant {
>  	/* Encoder Type for that controller */
>  	enum vc4_encoder_type encoder_type;
>  
> +	/* Filename to expose the registers in debugfs */
> +	const char *debugfs_name;
> +
>  	/* List of the registers available on that variant */
>  	const struct vc4_hdmi_register *registers;
>