Re: [PATCH 2/5] drm: of: introduce drm_of_find_panel_or_bridge

[Rob Herring]

On Mon, Feb 6, 2017 at 4:18 AM, Liviu Dudau <liviu.dudau@xxxxxxx> wrote:
> On Fri, Feb 03, 2017 at 09:36:32PM -0600, Rob Herring wrote:
>> Many drivers have a common pattern of searching the OF graph for either an
>> attached panel or bridge and then finding the DRM struct for the panel
>> or bridge. Also, most drivers need to handle deferred probing when the
>> DRM device is not yet instantiated. Create a common function,
>> drm_of_find_panel_or_bridge, to find the connected node and the
>> associated DRM panel or bridge device.
>>
>> Signed-off-by: Rob Herring <robh@xxxxxxxxxx>
>> ---
>>  drivers/gpu/drm/drm_of.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++
>>  include/drm/drm_of.h     | 13 +++++++++++++
>>  2 files changed, 63 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
>> index 47848ed8ca48..b29ce2f52113 100644
>> --- a/drivers/gpu/drm/drm_of.c
>> +++ b/drivers/gpu/drm/drm_of.c
>> @@ -3,7 +3,9 @@
>>  #include <linux/list.h>
>>  #include <linux/of_graph.h>
>>  #include <drm/drmP.h>
>> +#include <drm/drm_bridge.h>
>>  #include <drm/drm_crtc.h>
>> +#include <drm/drm_panel.h>
>>  #include <drm/drm_of.h>
>>
>>  static void drm_release_of(struct device *dev, void *data)
>> @@ -207,3 +209,51 @@ int drm_of_encoder_active_endpoint(struct device_node *node,
>>       return -EINVAL;
>>  }
>>  EXPORT_SYMBOL_GPL(drm_of_encoder_active_endpoint);
>> +
>> +/*
>> + * drm_of_find_panel_or_bridge - return connected panel or bridge device
>> + * @np: device tree node containing encoder input ports
>> + * @panel: pointer to hold returned drm_panel
>> + * @bridge: pointer to hold returned drm_bridge
>> + *
>> + * Given a DT node's port and endpoint number, find the connected node and
>> + * return either the associated struct drm_panel or drm_bridge device.
>> + *
>> + * Returns zero if successful, or one of the standard error codes if it fails.
>> + */
>> +int drm_of_find_panel_or_bridge(const struct device_node *np,
>> +                             int port, int endpoint,
>> +                             struct drm_panel **panel,
>> +                             struct drm_bridge **bridge)
>> +{
>> +     int ret = -ENODEV;
>
> Given that you never return 'ret' with -ENODEV can I suggest that you initialise 'ret'
> with -EPROBE_DEFER and then you can get rid of the two assignments further down?

But I can if both panel and bridge are NULL. I'm going with Philipp's
suggestion of -EINVAL here.

Rob