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)
--
Jani Nikula, Intel
