On 2019-08-20 5:02 p.m., Lyude Paul wrote:
[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?
I think this would work well.
drm_dp_mst_dpcd_read/write will eventually call drm_dp_dpcd_write, so doing so would cause a recursive call. That should be safe though. The mst manager's aux will be used, and that should always be a real (is_remote == false) aux, fwict.
Essentially, it's just moving that conditional from auxdev_read/write_iter to drm_dp_dpcd_read/write.
Leo
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@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) {