[PATCH v4] drm/connector: hdmi: Fix writing Dynamic Range Mastering infoframes

[Derek Foreman]

Gentle ping - is there anything more I need to do before this can land?

Thanks,
Derek

On 2024-08-28 03:31, Jani Nikula wrote:
> On Tue, 27 Aug 2024, Derek Foreman <derek.foreman at 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.
>>
>> Instead of having HDMI_MAX_INFOFRAME_SIZE defined in two places,
>> replace HDMI_MAX_INFOFRAME_SIZE with HDMI_INFOFRAME_SIZE(MAX) and make
>> MAX 27 bytes - which is defined by the HDMI specification to be the
>> largest infoframe payload.
>>
>> Fixes: f378b77227bc ("drm/connector: hdmi: Add Infoframes generation")
>> Fixes: c602e4959a0c ("drm/connector: hdmi: Create Infoframe DebugFS entries")
>>
> Superfluous blank line. Can be fixed while applying.
>
> Reviewed-by: Jani Nikula <jani.nikula at intel.com>
>
>
>> Signed-off-by: Derek Foreman <derek.foreman at collabora.com>
>> ---
>>   drivers/gpu/drm/display/drm_hdmi_state_helper.c | 4 +---
>>   drivers/gpu/drm/drm_debugfs.c                   | 4 +---
>>   include/linux/hdmi.h                            | 9 +++++++++
>>   3 files changed, 11 insertions(+), 6 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..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..455f855bc084 100644
>> --- a/include/linux/hdmi.h
>> +++ b/include/linux/hdmi.h
>> @@ -59,6 +59,15 @@ enum hdmi_infoframe_type {
>>   #define HDMI_DRM_INFOFRAME_SIZE    26
>>   #define HDMI_VENDOR_INFOFRAME_SIZE  4
>>   
>> +/*
>> + * HDMI 1.3a table 5-14 states that the largest InfoFrame_length is 27,
>> + * not including the packet header or checksum byte. We include the
>> + * checksum byte in HDMI_INFOFRAME_HEADER_SIZE, so this should allow
>> + * HDMI_INFOFRAME_SIZE(MAX) to be the largest buffer we could ever need
>> + * for any HDMI infoframe.
>> + */
>> +#define HDMI_MAX_INFOFRAME_SIZE    27
>> +
>>   #define HDMI_INFOFRAME_SIZE(type)	\
>>   	(HDMI_INFOFRAME_HEADER_SIZE + HDMI_ ## type ## _INFOFRAME_SIZE)