Re: [PATCH v3 15/26] drm/i915/writeback: Add connector atomic check

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Mar 25, 2026 at 04:37:33PM +0530, Suraj Kandpal wrote:
> Add connector helper function for atomic check which sets the
> mode_changed bit and checks if pixel format of fb is valid or not.
> 
> Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
> ---
>  .../gpu/drm/i915/display/intel_writeback.c    | 49 +++++++++++++++++++
>  1 file changed, 49 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_writeback.c b/drivers/gpu/drm/i915/display/intel_writeback.c
> index 86b53e4603ae..ba4c162847c8 100644
> --- a/drivers/gpu/drm/i915/display/intel_writeback.c
> +++ b/drivers/gpu/drm/i915/display/intel_writeback.c
> @@ -167,6 +167,54 @@ static void intel_writeback_connector_destroy(struct drm_connector *connector)
>  	kfree(connector);
>  }
>  
> +static int intel_writeback_check_format(u32 format)
> +{
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(writeback_formats); i++) {
> +		if (writeback_formats[i] == format)
> +			return 0;
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static int intel_writeback_atomic_check(struct drm_connector *connector,
> +					struct drm_atomic_state *state)
> +{
> +	struct drm_connector_state *conn_state =
> +		drm_atomic_get_new_connector_state(state, connector);
> +	struct drm_crtc_state *crtc_state;
> +	struct drm_framebuffer *fb;
> +	int ret;
> +
> +	/* We return 0 since this is called while disabling writeback encoder */
> +	if (!conn_state->crtc)
> +		return 0;
> +
> +	/* We do not allow a blank commit when using writeback connector */
> +	if (!conn_state->writeback_job)
> +		return -EINVAL;
> +
> +	fb = conn_state->writeback_job->fb;
> +	if (!fb)
> +		return -EINVAL;
> +
> +	crtc_state = drm_atomic_get_new_crtc_state(state, conn_state->crtc);
> +	if (fb->width != crtc_state->mode.hdisplay ||
> +	    fb->height != crtc_state->mode.vdisplay)
> +		return -EINVAL;
> +
> +	ret = intel_writeback_check_format(fb->format->format);
> +	if (ret) {
> +		drm_dbg_kms(connector->dev,
> +			    "Unsupported drm format sent in writeback job\n");
> +		return ret;
> +	}

Pretty much all of this look like something that belongs
in the core/helpers.

> +
> +	return 0;
> +}
> +
>  static const struct drm_encoder_funcs drm_writeback_encoder_funcs = {
>  	.destroy = drm_encoder_cleanup,
>  };
> @@ -182,6 +230,7 @@ const struct drm_connector_funcs conn_funcs = {
>  static const struct drm_connector_helper_funcs conn_helper_funcs = {
>  	.get_modes = intel_writeback_get_modes,
>  	.mode_valid = intel_writeback_mode_valid,
> +	.atomic_check = intel_writeback_atomic_check,
>  	.prepare_writeback_job = intel_writeback_prepare_job,
>  	.cleanup_writeback_job = intel_writeback_cleanup_job,
>  };
> -- 
> 2.34.1

-- 
Ville Syrjälä
Intel