Re: [PATCH i-g-t v4 28/46] lib/unigraf: Add helpers to read and write edid

["Luca Ceresoli" <luca.ceresoli@bootlin.com>]

On Mon Nov 10, 2025 at 2:39 PM CET, Louis Chauvet wrote:
> Read and writing EDID on unigraf can be useful to emulate different
> screens, add helpers to read and write them.
>
> There is a limitation on the libTSI.so, it is only possible to read EDID
> using buffers of size multiple of 128 bytes, and there is no way to query
> the actual EDID size. The current implementation can only read EDID up to
> 2048 bytes.
>
> Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
> ---
>  lib/unigraf/unigraf.c | 40 ++++++++++++++++++++++++++++++++++++++++
>  lib/unigraf/unigraf.h | 21 +++++++++++++++++++++
>  2 files changed, 61 insertions(+)
>
> diff --git a/lib/unigraf/unigraf.c b/lib/unigraf/unigraf.c
> index 9e77a052d755..2229202ea868 100644
> --- a/lib/unigraf/unigraf.c
> +++ b/lib/unigraf/unigraf.c
> @@ -125,6 +125,21 @@ static uint32_t _unigraf_read_u32(TSI_CONFIG_ID config_id)
>  		value;								\
>  	})
>
> +/**
> + * unigraf_write() - Helper to write a value to unigraf
> + * @dev: device handle, can be null for some config id

This function has no @dev parameter.

> + * @config: config id to write
> + * @data: data to write
> + * @data_len: length of the data
> + * Returns
> + */
> +static void unigraf_write(TSI_CONFIG_ID config, const void *data, size_t data_len)
> +{
> +	unigraf_debug("Writing %zu bytes to 0x%x\n", data_len, config);
> +
> +	unigraf_assert(TSIX_TS_SetConfigItem(unigraf_device, config, data, data_len));
> +}
> +
>  /**
>   * unigraf_device_count() - Return the number of scanned devices
>   *
> @@ -332,6 +347,31 @@ void unigraf_reset(void)
>  	unigraf_set_sst();
>  }
>
> +struct edid *unigraf_read_edid(uint32_t stream, uint32_t *edid_size)
> +{
> +	void *edid;
> +
> +	unigraf_debug("Read EDID for stream %d...\n", stream);
> +
> +	edid = malloc(2048);
> +	memset(edid, 0, 2048);
> +
> +	unigraf_write_u32(TSI_EDID_SELECT_STREAM, stream);
> +	*edid_size = unigraf_assert(TSIX_TS_GetConfigItem(unigraf_device,
> +							  TSI_EDID_TE_INPUT,
> +							  edid, 2048));
> +
> +	return edid;
> +}
> +
> +void unigraf_write_edid(uint32_t stream, const struct edid *edid, uint32_t edid_size)
> +{
> +	unigraf_debug("Write EDID for stream %d...\n", stream);
> +
> +	unigraf_write_u32(TSI_EDID_SELECT_STREAM, stream);
> +	unigraf_write(TSI_EDID_TE_INPUT, edid, 2048);
> +}
> +
>  void unigraf_hpd_assert(void)
>  {
>  	unigraf_write_u32(TSI_FORCE_HOT_PLUG_STATE_W, 1);
> diff --git a/lib/unigraf/unigraf.h b/lib/unigraf/unigraf.h
> index 9fcae674b1d5..983a21bbd61b 100644
> --- a/lib/unigraf/unigraf.h
> +++ b/lib/unigraf/unigraf.h
> @@ -57,6 +57,27 @@ void unigraf_require_device(int drm_fd);
>   */
>  void unigraf_reset(void);
>
> +/**
> + * unigraf_read_edid() - Read the EDID from the specified input

"from the specified stream"?

> + * @dev: The device handle

This function has no @dev parameter.

> + * @stream: The stream ID to read the EDID from
> + * @edid_size: Pointer to an integer where the size of the EDID will be stored
> + *
> + * Returns: A pointer to the EDID structure, or NULL if the operation failed. The caller
> + * is responsible to free this pointer.
> + */
> +struct edid *unigraf_read_edid(uint32_t stream, uint32_t *edid_size);

With the two @dev lines removed and the unigraf_read_edid() description fixed:
 Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>

Luca

--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com