drm: docs: Update task from drm TODO list

Level: Intermediate

Transition away from using mipi_dsi_*_write_seq()

-------------------------------------------------

The macros mipi_dsi_generic_write_seq() and mipi_dsi_dcs_write_seq() are

non-intuitive because, if there are errors, they return out of the *caller's*

function. We should move all callers to use mipi_dsi_generic_write_seq_multi()

and mipi_dsi_dcs_write_seq_multi() macros instead.

Once all callers are transitioned, the macros and the functions that they call,

mipi_dsi_generic_write_chatty() and mipi_dsi_dcs_write_buffer_chatty(), can

probably be removed. Alternatively, if people feel like the _multi() variants

are overkill for some use cases, we could keep the mipi_dsi_*_write_seq()

variants but change them not to return out of the caller.

Transition away from using deprecated MIPI DSI functions

--------------------------------------------------------

There are many functions defined in ``drm_mipi_dsi.c`` which have been

deprecated. Each deprecated function was deprecated in favor of its `multi`

variant (e.g. `mipi_dsi_generic_write()` and `mipi_dsi_generic_write_multi()`).

The `multi` variant of a function includes improved error handling and logic

which makes it more convenient to make several calls in a row, as most MIPI

drivers do.

Drivers should be updated to use undeprecated functions. Once all usages of the

deprecated MIPI DSI functions have been removed, their definitions may be

removed from ``drm_mipi_dsi.c``.

Contact: Douglas Anderson <dianders@chromium.org>