[PATCH RFC 1/9] drm/omap: Update omapdss API to allow alternative DSS implementations

[Laurent Pinchart]

Hi Tomi,

On Monday, 19 February 2018 14:01:05 EET Tomi Valkeinen wrote:
> On 16/02/18 13:25, Jyri Sarha wrote:
> > After this patch OMAP_DSS_BASE module is not including any OMAP2_DSS
> > headers, only the API omapdss.h. "sturct dss_data", the piece of the
> > data structure needed for base.c is defined in omapdss.h and added as
> > a member to struct dss_device, and later to struct dss6_device.
> > 
> > The patch is still a bit hackish. The struct dispc_device declaration
> > is currently shared between alternative dss implementations, with
> > different internal definitions. It should be relatively simple to use
> > a similar struct dispc_data as struct dss_data is for dss_device, move
> > some common parts - maybe the dispc_ops itself - there and find the
> > private data with container_of macro. Also the contents of struct
> > dss_data in side dss_device is currently redundant. These should be
> > easy enough to fix, if we decide to take this route.
> > 
> > Signed-off-by: Jyri Sarha <jsarha at ti.com>
> > ---
> > 
> >  drivers/gpu/drm/omapdrm/dss/base.c    | 11 +++++------
> >  drivers/gpu/drm/omapdrm/dss/dispc.c   |  4 ++++
> >  drivers/gpu/drm/omapdrm/dss/dss.c     |  2 +-
> >  drivers/gpu/drm/omapdrm/dss/dss.h     |  2 ++
> >  drivers/gpu/drm/omapdrm/dss/omapdss.h | 13 +++++++++----
> >  drivers/gpu/drm/omapdrm/omap_drv.h    |  2 +-
> >  6 files changed, 22 insertions(+), 12 deletions(-)
> 
> I think something in this direction would be good. I'd really like to keep
> it possible to run dss6 on top of omapdrm.
> 
> But I think this can be done slightly simpler like this:
> 
> 
> diff --git a/drivers/gpu/drm/omapdrm/dss/base.c
> b/drivers/gpu/drm/omapdrm/dss/base.c index 99e8cb8dc65b..08913e006e93
> 100644
> --- a/drivers/gpu/drm/omapdrm/dss/base.c
> +++ b/drivers/gpu/drm/omapdrm/dss/base.c
> @@ -19,10 +19,11 @@
>  #include <linux/of_graph.h>
>  #include <linux/list.h>
> 
> -#include "dss.h"
>  #include "omapdss.h"
> 
>  static struct dss_device *dss_device;
> +static struct dispc_device *s_dispc_device;
> +static const struct dispc_ops *s_dispc_ops;
> 
>  static struct list_head omapdss_comp_list;
> 
> @@ -46,16 +47,23 @@ EXPORT_SYMBOL(omapdss_set_dss);
> 
>  struct dispc_device *dispc_get_dispc(struct dss_device *dss)
>  {
> -	return dss->dispc;
> +	return s_dispc_device;
>  }
>  EXPORT_SYMBOL(dispc_get_dispc);
> 
>  const struct dispc_ops *dispc_get_ops(struct dss_device *dss)
>  {
> -	return dss->dispc_ops;
> +	return s_dispc_ops;
>  }
>  EXPORT_SYMBOL(dispc_get_ops);
> 
> +void omapdss_set_dispc(struct dispc_device *dispc, const struct dispc_ops*
> dispc_ops)
> +{
> +	s_dispc_device = dispc;
> +	s_dispc_ops = dispc_ops;
> +}
> +EXPORT_SYMBOL(omapdss_set_dispc);
> +
>  static bool omapdss_list_contains(const struct device_node *node)
>  {
>  	struct omapdss_comp_node *comp;
> diff --git a/drivers/gpu/drm/omapdrm/dss/dispc.c
> b/drivers/gpu/drm/omapdrm/dss/dispc.c index ce470b51e326..b72f981d660e
> 100644
> --- a/drivers/gpu/drm/omapdrm/dss/dispc.c
> +++ b/drivers/gpu/drm/omapdrm/dss/dispc.c
> @@ -4786,7 +4786,7 @@ static int dispc_bind(struct device *dev, struct
> device *master, void *data) dispc_runtime_put(dispc);
> 
>  	dss->dispc = dispc;
> -	dss->dispc_ops = &dispc_ops;
> +	omapdss_set_dispc(dispc, &dispc_ops);
> 
>  	dispc->debugfs = dss_debugfs_create_file(dss, "dispc", dispc_dump_regs,
>  						 dispc);
> @@ -4807,8 +4807,8 @@ static void dispc_unbind(struct device *dev, struct
> device *master, void *data)
> 
>  	dss_debugfs_remove_file(dispc->debugfs);
> 
> +	omapdss_set_dispc(NULL, NULL);
>  	dss->dispc = NULL;
> -	dss->dispc_ops = NULL;
> 
>  	pm_runtime_disable(dev);
> 
> diff --git a/drivers/gpu/drm/omapdrm/dss/dss.h
> b/drivers/gpu/drm/omapdrm/dss/dss.h index 6f6fd3d1b159..3d23232ec1f7 100644
> --- a/drivers/gpu/drm/omapdrm/dss/dss.h
> +++ b/drivers/gpu/drm/omapdrm/dss/dss.h
> @@ -274,7 +274,6 @@ struct dss_device {
>  	struct dss_pll	*video2_pll;
> 
>  	struct dispc_device *dispc;
> -	const struct dispc_ops *dispc_ops;
>  };
> 
>  /* core */
> diff --git a/drivers/gpu/drm/omapdrm/dss/omapdss.h
> b/drivers/gpu/drm/omapdrm/dss/omapdss.h index a4f71e082c1c..b724dae22d7a
> 100644
> --- a/drivers/gpu/drm/omapdrm/dss/omapdss.h
> +++ b/drivers/gpu/drm/omapdrm/dss/omapdss.h
> @@ -751,6 +751,7 @@ struct dispc_ops {
> 
>  struct dispc_device *dispc_get_dispc(struct dss_device *dss);
>  const struct dispc_ops *dispc_get_ops(struct dss_device *dss);
> +void omapdss_set_dispc(struct dispc_device *dispc, const struct dispc_ops*
> dispc_ops);
> 
>  bool omapdss_component_is_display(struct device_node *node);
>  bool omapdss_component_is_output(struct device_node *node);
> 
> 
> Yes, it adds two new globals. But I don't think those are a big issue. Note
> that I left the dss->dispc there, for dss internal use.
> 
> Laurent, what do you think? If this is fine, can you squash to your series?
> Or I can even have this on top as well. I think otherwise it's good for
> merging.

To be honest I like Jyri's approach better, with a small caveat: we really 
need to standardize how we name our data structures. It will be painful (as in 
generating conflicts) but should make the code much clearer. dss_data vs. 
dss_device vs. omap_dss_device is just too confusing. If you agree to a rename 
of data structure I'll make a proposal.

Additionally, one thing I like about this patch is that the dss_data structure 
(to be renamed...) can store data shared between the DSS2-5 and DSS6 
implementations, which would make it easier to share code where applicable. 
Being completely honest again I haven't reviewed the DSS6 implementation yet, 
so there might be no opportunity for code sharing.

> Can you also have a quick look at patches 2, 3, 4, 5, 6 and 7. While their
> aim is to get dss6 working, I think they're ok cleanups and shouldn't cause
> issues with the main dss rework.

Sure, I'll review them now.

-- 
Regards,

Laurent Pinchart