[PATCH 2/3] drm: Add Wrapper Functions for ELD SAD Extraction
Jani Nikula
jani.nikula at intel.com
Thu Sep 7 09:35:52 UTC 2023
On Mon, 21 Aug 2023, Mitul Golani <mitulkumar.ajitkumar.golani at intel.com> wrote:
> Add wrapper functions to facilitate extracting Short Audio
> Descriptor (SAD) information from EDID-Like Data (ELD) pointers
> with different constness requirements.
>
> 1. `drm_eld_sad`: This function returns a constant `uint8_t`
> pointer and wraps the main extraction function, allowing access
> to SAD information while maintaining const correctness.
>
> 2. `drm_extract_sad_from_eld`: This function returns a mutable
> `uint8_t` pointer and implements the core logic for extracting
> SAD from the provided ELD pointer. It performs version and
> maximum channel checks to ensure proper extraction.
>
> These wrapper functions provide flexibility to the codebase,
> allowing users to access SAD information while adhering to
> const correctness when needed and modifying the pointer when
> required.
I've considered this, and in the end I think it's better to *not* make
it easier for drivers to modify the ELD buffer directly.
To that end, I wrote some helpers to modify the SADs using the existing
struct cea_sad abstraction [1]. Please have a look. It should make your
changes better focus on what you need to do here, instead of getting
distracted with ELD parsing details.
BR,
Jani.
[1] https://patchwork.freedesktop.org/series/123384/
>
> Signed-off-by: Mitul Golani <mitulkumar.ajitkumar.golani at intel.com>
> ---
> include/drm/drm_edid.h | 15 ++++++++++-----
> 1 file changed, 10 insertions(+), 5 deletions(-)
>
> diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
> index 48e93f909ef6..626bc0d542eb 100644
> --- a/include/drm/drm_edid.h
> +++ b/include/drm/drm_edid.h
> @@ -418,11 +418,7 @@ static inline int drm_eld_mnl(const uint8_t *eld)
> return (eld[DRM_ELD_CEA_EDID_VER_MNL] & DRM_ELD_MNL_MASK) >> DRM_ELD_MNL_SHIFT;
> }
>
> -/**
> - * drm_eld_sad - Get ELD SAD structures.
> - * @eld: pointer to an eld memory structure with sad_count set
> - */
> -static inline const uint8_t *drm_eld_sad(const uint8_t *eld)
> +static uint8_t *drm_extract_sad_from_eld(uint8_t *eld)
> {
> unsigned int ver, mnl;
>
> @@ -437,6 +433,15 @@ static inline const uint8_t *drm_eld_sad(const uint8_t *eld)
> return eld + DRM_ELD_CEA_SAD(mnl, 0);
> }
>
> +/**
> + * drm_eld_sad - Get ELD SAD structures.
> + * @eld: pointer to an eld memory structure with sad_count set
> + */
> +static inline const uint8_t *drm_eld_sad(const uint8_t *eld)
> +{
> + return drm_extract_sad_from_eld((uint8_t *)eld);
> +}
> +
> /**
> * drm_eld_sad_count - Get ELD SAD count.
> * @eld: pointer to an eld memory structure with sad_count set
--
Jani Nikula, Intel Open Source Graphics Center
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