Re: [PATCH v3 1/4] drm/simple-kms: Add drm_simple_encoder_{init, create}()

[Sam Ravnborg <sam@ravnborg.org>]

On Tue, Feb 25, 2020 at 02:10:52PM +0100, Thomas Zimmermann wrote:
> This patch makes the internal encoder implementation of the simple
> KMS helpers available to drivers.
> 
> These simple-encoder helpers initialize an encoder with an empty
> implementation. This covers the requirements of most of the existing
> DRM drivers. A call to drm_simple_encoder_create() allocates and
> initializes an encoder instance, a call to drm_simple_encoder_init()
> initializes a pre-allocated instance.
> 
> v3:
> 	* remove drm_simple_encoder_create(); not required yet
> 	* provide more precise documentation
> v2:
> 	* move simple encoder to KMS helpers
> 	* remove name argument; simplifies implementation
> 	* don't allocate with devm_ interfaces; unsafe with DRM
> 
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
> ---
>  drivers/gpu/drm/drm_simple_kms_helper.c | 34 ++++++++++++++++++++++---
>  include/drm/drm_simple_kms_helper.h     |  4 +++
>  2 files changed, 35 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
> index 15fb516ae2d8..04309e4660de 100644
> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
> @@ -26,12 +26,41 @@
>   * entity. Some flexibility for code reuse is provided through a separately
>   * allocated &drm_connector object and supporting optional &drm_bridge
>   * encoder drivers.
> + *
> + * Many drivers require only a very simple encoder that fulfills the minimum
> + * requirements of the display pipeline and does not add additional
> + * functionality. The function drm_simple_encoder_init() provides an
> + * implementation of such an encoder.
>   */
>  
> -static const struct drm_encoder_funcs drm_simple_kms_encoder_funcs = {
> +static const struct drm_encoder_funcs drm_simple_encoder_funcs_cleanup = {
>  	.destroy = drm_encoder_cleanup,
>  };
>  
> +/**
> + * drm_simple_encoder_init - Initialize a preallocated encoder
> + * @dev: drm device
> + * @funcs: callbacks for this encoder
> + * @encoder_type: user visible type of the encoder
> + *
> + * Initialises a preallocated encoder that has no further functionality.
> + * Settings for possible CRTC and clones are left to their initial values.
> + * The encoder will be cleaned up automatically as part of the mode-setting
> + * cleanup.
> + *
> + * Returns:
> + * Zero on success, error code on failure.
> + */
> +int drm_simple_encoder_init(struct drm_device *dev,
> +			    struct drm_encoder *encoder,
> +			    int encoder_type)
> +{
> +	return drm_encoder_init(dev, encoder,
> +				&drm_simple_encoder_funcs_cleanup,
> +				encoder_type, NULL);
> +}
> +EXPORT_SYMBOL(drm_simple_encoder_init);
> +
>  static enum drm_mode_status
>  drm_simple_kms_crtc_mode_valid(struct drm_crtc *crtc,
>  			       const struct drm_display_mode *mode)
> @@ -288,8 +317,7 @@ int drm_simple_display_pipe_init(struct drm_device *dev,
>  		return ret;
>  
>  	encoder->possible_crtcs = drm_crtc_mask(crtc);
> -	ret = drm_encoder_init(dev, encoder, &drm_simple_kms_encoder_funcs,
> -			       DRM_MODE_ENCODER_NONE, NULL);
> +	ret = drm_simple_encoder_init(dev, encoder, DRM_MODE_ENCODER_NONE);
>  	if (ret || !connector)
>  		return ret;
>  
> diff --git a/include/drm/drm_simple_kms_helper.h b/include/drm/drm_simple_kms_helper.h
> index e253ba7bea9d..a026375464ff 100644
> --- a/include/drm/drm_simple_kms_helper.h
> +++ b/include/drm/drm_simple_kms_helper.h
> @@ -181,4 +181,8 @@ int drm_simple_display_pipe_init(struct drm_device *dev,
>  			const uint64_t *format_modifiers,
>  			struct drm_connector *connector);
>  
> +int drm_simple_encoder_init(struct drm_device *dev,
> +			    struct drm_encoder *encoder,
> +			    int encoder_type);
> +
>  #endif /* __LINUX_DRM_SIMPLE_KMS_HELPER_H */
> -- 
> 2.25.0
> 
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