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

[Jani Nikula]

On Mon, 16 Sep 2024, Derek Foreman <derek.foreman at collabora.com> wrote:
> Gentle ping - is there anything more I need to do before this can land?

I don't think so. FWIW, I bounced this to intel-gfx and got passing CI
results too.

Cc: drm-misc maintainers. Just wondering where to merge this. It's a fix
to commits in v6.11. Are you still planning on a drm-misc-next-fixes
pull request for v6.12-rc1? That would be the quickest way to get this
upstream.

BR,
Jani.


>
> 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)

-- 
Jani Nikula, Intel