[PATCH 18/28] drm/i915/writeback: Add connector atomic check

[Dmitry Baryshkov]

On Fri, Jul 25, 2025 at 10:33:59AM +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 at 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 9b2432d86d35..7fb30cc61991 100644
> --- a/drivers/gpu/drm/i915/display/intel_writeback.c
> +++ b/drivers/gpu/drm/i915/display/intel_writeback.c
> @@ -186,6 +186,54 @@ 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;

Other atomic_check functions return 0 if there is no writeback_job or no
FB. Please elaborate.

> +
> +	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;
> +	}

Missing a call to drm_atomic_helper_check_wb_connector_state(). Please
use the framework where available.

> +
> +	return 0;
> +}
> +
>  static struct drm_writeback_connector *
>  intel_get_writeback_connector(struct drm_connector *connector)
>  {
> @@ -221,6 +269,7 @@ static const struct drm_connector_helper_funcs conn_helper_funcs = {
>  	.get_writeback_connector = intel_get_writeback_connector,
>  	.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
> 

-- 
With best wishes
Dmitry