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

[Derek Foreman <derek.foreman@xxxxxxxxxxxxx>]

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@xxxxxxxxxxxxx> 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@xxxxxxxxx>
>
>
> > Signed-off-by: Derek Foreman <derek.foreman@xxxxxxxxxxxxx>
> > ---
> >   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)