Re: [PATCH v2] drm/connector: hdmi: Increase HDMI_MAX_INFOFRAME_SIZE to 30

[Jani Nikula <jani.nikula@linux.intel.com>]

On Fri, 23 Aug 2024, Derek Foreman <derek.foreman@collabora.com> wrote:
> The largest infoframe we create is the DRM (Dynamic Range Mastering)
> infoframe which is 26 bytes + a 4 byte header, for a total of 30
> bytes.
>
> With HDMI_MAX_INFOFRAME_SIZE set to 29 bytes, as it is now, we
> allocate too little space to pack a DRM infoframe in
> write_device_infoframe(), leading to an ENOSPC return from
> hdmi_infoframe_pack(), and never calling the connector's
> write_infoframe() vfunc.
>
> Increase HDMI_MAX_INFOFRAME_SIZE to 30 so we can successfully
> write DRM infoframes.
>
> The drm_debugfs code is similarly updated.
>
> Signed-off-by: Derek Foreman <derek.foreman@collabora.com>

Okay, thanks for the info. Looking into it, I think keeping this in two
places and disconnected from the actual infoframe size definitions is
hard to maintain. Maybe something like this:


diff --git a/drivers/gpu/drm/display/drm_hdmi_state_helper.c b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
index 7854820089ec..feb7a3a75981 100644
--- a/drivers/gpu/drm/display/drm_hdmi_state_helper.c
+++ b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
@@ -521,8 +521,6 @@ int drm_atomic_helper_connector_hdmi_check(struct drm_connector *connector,
 }
 EXPORT_SYMBOL(drm_atomic_helper_connector_hdmi_check);
 
-#define HDMI_MAX_INFOFRAME_SIZE		29
-
 static int clear_device_infoframe(struct drm_connector *connector,
 				  enum hdmi_infoframe_type type)
 {
@@ -563,7 +561,7 @@ static int write_device_infoframe(struct drm_connector *connector,
 {
 	const struct drm_connector_hdmi_funcs *funcs = connector->hdmi.funcs;
 	struct drm_device *dev = connector->dev;
-	u8 buffer[HDMI_MAX_INFOFRAME_SIZE];
+	u8 buffer[HDMI_INFOFRAME_SIZE(MAX)];
 	int ret;
 	int len;
 
diff --git a/drivers/gpu/drm/drm_debugfs.c b/drivers/gpu/drm/drm_debugfs.c
index 6b239a24f1df..9d3e6dd68810 100644
--- a/drivers/gpu/drm/drm_debugfs.c
+++ b/drivers/gpu/drm/drm_debugfs.c
@@ -520,8 +520,6 @@ static const struct file_operations drm_connector_fops = {
 	.write = connector_write
 };
 
-#define HDMI_MAX_INFOFRAME_SIZE		29
-
 static ssize_t
 audio_infoframe_read(struct file *filp, char __user *ubuf, size_t count, loff_t *ppos)
 {
@@ -579,7 +577,7 @@ static ssize_t _f##_read_infoframe(struct file *filp, \
 	struct drm_connector *connector; \
 	union hdmi_infoframe *frame; \
 	struct drm_device *dev; \
-	u8 buf[HDMI_MAX_INFOFRAME_SIZE]; \
+	u8 buf[HDMI_INFOFRAME_SIZE(MAX)]; \
 	ssize_t len = 0; \
 	\
 	connector = filp->private_data; \
diff --git a/include/linux/hdmi.h b/include/linux/hdmi.h
index 3bb87bf6bc65..3a442a59919e 100644
--- a/include/linux/hdmi.h
+++ b/include/linux/hdmi.h
@@ -59,6 +59,9 @@ enum hdmi_infoframe_type {
 #define HDMI_DRM_INFOFRAME_SIZE    26
 #define HDMI_VENDOR_INFOFRAME_SIZE  4
 
+/* The biggest infoframe size */
+#define HDMI_MAX_INFOFRAME_SIZE		HDMI_DRM_INFOFRAME_SIZE
+
 #define HDMI_INFOFRAME_SIZE(type)	\
 	(HDMI_INFOFRAME_HEADER_SIZE + HDMI_ ## type ## _INFOFRAME_SIZE)
 



> ---
>  drivers/gpu/drm/display/drm_hdmi_state_helper.c | 2 +-
>  drivers/gpu/drm/drm_debugfs.c                   | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/display/drm_hdmi_state_helper.c b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> index 7854820089ec..cc7747d33fdf 100644
> --- a/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> +++ b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> @@ -521,7 +521,7 @@ int drm_atomic_helper_connector_hdmi_check(struct drm_connector *connector,
>  }
>  EXPORT_SYMBOL(drm_atomic_helper_connector_hdmi_check);
>  
> -#define HDMI_MAX_INFOFRAME_SIZE		29
> +#define HDMI_MAX_INFOFRAME_SIZE		30
>  
>  static int clear_device_infoframe(struct drm_connector *connector,
>  				  enum hdmi_infoframe_type type)
> diff --git a/drivers/gpu/drm/drm_debugfs.c b/drivers/gpu/drm/drm_debugfs.c
> index 6b239a24f1df..3439fd65275a 100644
> --- a/drivers/gpu/drm/drm_debugfs.c
> +++ b/drivers/gpu/drm/drm_debugfs.c
> @@ -520,7 +520,7 @@ static const struct file_operations drm_connector_fops = {
>  	.write = connector_write
>  };
>  
> -#define HDMI_MAX_INFOFRAME_SIZE		29
> +#define HDMI_MAX_INFOFRAME_SIZE		30
>  
>  static ssize_t
>  audio_infoframe_read(struct file *filp, char __user *ubuf, size_t count, loff_t *ppos)

-- 
Jani Nikula, Intel