Re: [PATCH 2/6] drm: Add drm_simple_encoder_{init,create}()

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Feb 07, 2020 at 03:02:00PM +0100, Thomas Zimmermann wrote:
> Hi
> 
> Am 07.02.20 um 14:37 schrieb Daniel Vetter:
> > On Fri, Feb 07, 2020 at 09:41:31AM +0100, Thomas Zimmermann wrote:
> >> The 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.
> >>
> >> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> > 
> > This has quick a bit midlayer taste to it ... I think having this as a
> > helper would be cleaner ...
> 
> How would such a helper roughly look like?

Essentially same code, but stuff the helper into drm-kms-helper.ko, then
make sure it still works. The separate kernel module makes sure that the
drm core and helper stuff aren't too close friends with each another :-)
Essentially like the simple display pipe helpers.
-Daniel

> 
> Best regards
> Thomas
> 
> > 
> > The other bit is drm_encoder->possible_crtcs. If we do create a helper for
> > these, lets at least try to make them not suck too badly :-) Otherwise I
> > guess it would be time to officially document what exactly possible_crtcs
> > == 0 means from an uabi pov.
> > -Daniel
> > 
> >> ---
> >>  drivers/gpu/drm/drm_encoder.c | 116 ++++++++++++++++++++++++++++++++++
> >>  include/drm/drm_encoder.h     |  10 +++
> >>  2 files changed, 126 insertions(+)
> >>
> >> diff --git a/drivers/gpu/drm/drm_encoder.c b/drivers/gpu/drm/drm_encoder.c
> >> index ffe691a1bf34..1a65cab1f310 100644
> >> --- a/drivers/gpu/drm/drm_encoder.c
> >> +++ b/drivers/gpu/drm/drm_encoder.c
> >> @@ -178,6 +178,122 @@ int drm_encoder_init(struct drm_device *dev,
> >>  }
> >>  EXPORT_SYMBOL(drm_encoder_init);
> >>  
> >> +static const struct drm_encoder_funcs drm_simple_encoder_funcs_cleanup = {
> >> +	.destroy = drm_encoder_cleanup,
> >> +};
> >> +
> >> +/**
> >> + * drm_simple_encoder_init - Init a preallocated encoder
> >> + * @dev: drm device
> >> + * @funcs: callbacks for this encoder
> >> + * @encoder_type: user visible type of the encoder
> >> + * @name: printf style format string for the encoder name, or NULL
> >> + *        for default name
> >> + *
> >> + * Initialises a preallocated encoder that has no further functionality. The
> >> + * encoder will be released automatically.
> >> + *
> >> + * Returns:
> >> + * Zero on success, error code on failure.
> >> + */
> >> +int drm_simple_encoder_init(struct drm_device *dev,
> >> +			    struct drm_encoder *encoder,
> >> +			    int encoder_type, const char *name, ...)
> >> +{
> >> +	char *namestr = NULL;
> >> +	int ret;
> >> +
> >> +	if (name) {
> >> +		va_list ap;
> >> +
> >> +		va_start(ap, name);
> >> +		namestr = kvasprintf(GFP_KERNEL, name, ap);
> >> +		va_end(ap);
> >> +		if (!namestr)
> >> +			return -ENOMEM;
> >> +	}
> >> +
> >> +	ret = __drm_encoder_init(dev, encoder,
> >> +				 &drm_simple_encoder_funcs_cleanup,
> >> +				 encoder_type, namestr);
> >> +	if (ret)
> >> +		goto err_kfree;
> >> +
> >> +	return 0;
> >> +
> >> +err_kfree:
> >> +	if (name)
> >> +		kfree(namestr);
> >> +	return ret;
> >> +}
> >> +EXPORT_SYMBOL(drm_simple_encoder_init);
> >> +
> >> +static void drm_encoder_destroy(struct drm_encoder *encoder)
> >> +{
> >> +	struct drm_device *dev = encoder->dev;
> >> +
> >> +	drm_encoder_cleanup(encoder);
> >> +	devm_kfree(dev->dev, encoder);
> >> +}
> >> +
> >> +static const struct drm_encoder_funcs drm_simple_encoder_funcs_destroy = {
> >> +	.destroy = drm_encoder_destroy,
> >> +};
> >> +
> >> +/**
> >> + * drm_simple_encoder_create - Allocate and initialize an encoder
> >> + * @dev: drm device
> >> + * @encoder_type: user visible type of the encoder
> >> + * @name: printf style format string for the encoder name, or NULL for
> >> + *        default name
> >> + *
> >> + * Allocates and initialises an encoder that has no further functionality. The
> >> + * encoder will be released automatically.
> >> + *
> >> + * Returns:
> >> + * The encoder on success, a pointer-encoder error code on failure.
> >> + */
> >> +struct drm_encoder *drm_simple_encoder_create(struct drm_device *dev,
> >> +					      int encoder_type,
> >> +					      const char *name, ...)
> >> +{
> >> +	char *namestr = NULL;
> >> +	struct drm_encoder *encoder;
> >> +	int ret;
> >> +
> >> +	encoder = devm_kzalloc(dev->dev, sizeof(*encoder), GFP_KERNEL);
> >> +	if (!encoder)
> >> +		return ERR_PTR(-ENOMEM);
> >> +
> >> +	if (name) {
> >> +		va_list ap;
> >> +
> >> +		va_start(ap, name);
> >> +		namestr = kvasprintf(GFP_KERNEL, name, ap);
> >> +		va_end(ap);
> >> +		if (!namestr) {
> >> +			ret = -ENOMEM;
> >> +			goto err_devm_kfree;
> >> +		}
> >> +	}
> >> +
> >> +	ret = __drm_encoder_init(dev, encoder,
> >> +				 &drm_simple_encoder_funcs_destroy,
> >> +				 encoder_type, namestr);
> >> +	if (ret)
> >> +		goto err_kfree;
> >> +
> >> +	return encoder;
> >> +
> >> +err_kfree:
> >> +	if (name)
> >> +		kfree(namestr);
> >> +err_devm_kfree:
> >> +	devm_kfree(dev->dev, encoder);
> >> +	return ERR_PTR(ret);
> >> +}
> >> +EXPORT_SYMBOL(drm_simple_encoder_create);
> >> +
> >>  /**
> >>   * drm_encoder_cleanup - cleans up an initialised encoder
> >>   * @encoder: encoder to cleanup
> >> diff --git a/include/drm/drm_encoder.h b/include/drm/drm_encoder.h
> >> index 5623994b6e9e..0214f6cf9de6 100644
> >> --- a/include/drm/drm_encoder.h
> >> +++ b/include/drm/drm_encoder.h
> >> @@ -190,6 +190,16 @@ int drm_encoder_init(struct drm_device *dev,
> >>  		     const struct drm_encoder_funcs *funcs,
> >>  		     int encoder_type, const char *name, ...);
> >>  
> >> +__printf(4, 5)
> >> +int drm_simple_encoder_init(struct drm_device *dev,
> >> +			    struct drm_encoder *encoder,
> >> +			    int encoder_type, const char *name, ...);
> >> +
> >> +__printf(3, 4)
> >> +struct drm_encoder *drm_simple_encoder_create(struct drm_device *dev,
> >> +					      int encoder_type,
> >> +					      const char *name, ...);
> >> +
> >>  /**
> >>   * drm_encoder_index - find the index of a registered encoder
> >>   * @encoder: encoder to find index for
> >> -- 
> >> 2.25.0
> >>
> > 
> 
> -- 
> Thomas Zimmermann
> Graphics Driver Developer
> SUSE Software Solutions Germany GmbH
> Maxfeldstr. 5, 90409 Nürnberg, Germany
> (HRB 36809, AG Nürnberg)
> Geschäftsführer: Felix Imendörffer
> 




-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch