Re: [PATCH v3 01/22] drm: Include ddc adapter pointer in struct drm_connector

[Andrzej Pietrasiewicz <andrzej.p-ZGY8ohtN/8qB+jHODAdFcQ@public.gmane.org>]

Hi Thomas,

Thank you for your comments. Please see inline.

W dniu 30.06.2019 o 10:12, Thomas Zimmermann pisze:
> Hi
> 
> I like the idea, but would prefer a more structured approach.
> 
> Setting connector->ddc before calling drm_sysfs_connector_add() seems
> error prone. The dependency is not really clear from the code or interfaces.
> 
> The other thing is that drivers I mostly work on, ast and mgag200, have
> code like this:
> 
>    struct ast_i2c_chan {
> 	struct i2c_adapter adapter;
> 	struct drm_device *dev;
> 	struct i2c_algo_bit_data bit;
>    };
> 
>    struct ast_connector {
> 	struct drm_connector base;
> 	struct ast_i2c_chan *i2c;
>    };
> 
> It already encodes the connection between connector and ddc adapter.
> 
> I suggest to introduce struct drm_i2c_adapter
> 
>    struct drm_i2c_adapter {
> 	struct i2c_adapter base;
> 	struct drm_connector *connector;
>    };
> 
> and convert drivers over to it. Ast would look like this:
> 
>    struct ast_i2c_chan {
> 	struct drm_i2c_adapter adapter;
> 	struct i2c_algo_bit_data bit;
>    };
> 

There are few flavors of these drivers. In some of them
the i2c_adapter for ddc is allocated and initialized by
the driver, which must provide a place in memory to hold
the adapter. ast is an example of this approach.

But there are others, such as for example exynos_hdmi.c.
It gets its ddc adapter with of_find_i2c_adapter_by_node()
and merely stores a pointer to it, while not managing the
memory needed to hold the i2c_adapter.

Do you have any idea how to accommodate these various
flavors of drivers in the scheme you propose?

Andrzej


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