[PATCH v2 09/14] drm/dp-mst: Export symbols for dpcd read/write

[Lyude Paul]

[Added Leo Li here, since they did the auxdev work that introduced these
functions]

Since it seems we'll actually be doing remote DPCD read/writes in DRM drivers
and not just from auxdev, maybe we should combine drm_dp_dpcd_read() with
drm_dp_mst_dpcd_read() and do the same with the _write() variants? Based on
previous discussions with Leo Li I remember that we can't just combine the
dp_aux_dev->transfer() callbacks in struct drm_dp_aux_dev, but I don't see a
reason we can't just teach drm_dp_dpcd_read/write() to work with MST aux so
that we don't need two seperate functions. This should be pretty easy to do,
just:

/* Add a check like this at the start of drm_dp_dpcd_read(): */
ssize_t drm_dp_dpcd_read(...) {
	if (aux->is_remote)
		return drm_dp_mst_dpcd_read(...);

	/* ... */
}

/* And in drm_dp_dpcd_write(): */
ssize_t drm_dp_dpcd_write(...) {
	if (aux->is_remote)
		return drm_dp_mst_dpcd_write(...);

	/* ... */
}

Then just replace the manual calls to drm_dp_mst_dpcd_write() in
drivers/gpu/drm/drm_dp_aux_dev.c with normal
drm_dp_dpcd_read()/drm_dp_dpcd_write() calls. Thoughts?

On Tue, 2019-08-20 at 15:11 -0400, David Francis wrote:
> To use these functions in drm driver directories, they must be
> exported
> 
> Signed-off-by: David Francis <David.Francis at amd.com>
> ---
>  drivers/gpu/drm/drm_dp_mst_topology.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
> b/drivers/gpu/drm/drm_dp_mst_topology.c
> index b40d975aec76..5d5bd42da17c 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -1512,6 +1512,7 @@ ssize_t drm_dp_mst_dpcd_read(struct drm_dp_aux *aux,
>  	return drm_dp_send_dpcd_read(port->mgr, port,
>  				     offset, size, buffer);
>  }
> +EXPORT_SYMBOL(drm_dp_mst_dpcd_read);
>  
>  /**
>   * drm_dp_mst_dpcd_write() - write a series of bytes to the DPCD via
> sideband
> @@ -1535,6 +1536,7 @@ ssize_t drm_dp_mst_dpcd_write(struct drm_dp_aux *aux,
>  	return drm_dp_send_dpcd_write(port->mgr, port,
>  				      offset, size, buffer);
>  }
> +EXPORT_SYMBOL(drm_dp_mst_dpcd_write);
>  
>  static void drm_dp_check_mstb_guid(struct drm_dp_mst_branch *mstb, u8
> *guid)
>  {
-- 
Cheers,
	Lyude Paul