[PATCH] drm/i2c: tda998x: Choose between atomic or non atomic dpms helper

[Liviu.Dudau at arm.com]

On Sat, Jan 16, 2016 at 10:17:54PM +0200, Jyri Sarha wrote:
> Choose between atomic or non atomic connector dpms helper. If tda998x
> is connected to a drm driver that does not support atomic modeset
> calling drm_atomic_helper_connector_dpms() causes a crash when the
> connectors atomic state is not initialized. The patch implements a
> driver specific connector dpms helper that calls
> drm_atomic_helper_connector_dpms() if driver supports DRIVER_ATOMIC
> and otherwise it calls the legacy drm_helper_connector_dpms().
> 
> Fixes commit 9736e988d328 ("drm/i2c: tda998x: Add support for atomic
> modesetting").
> 
> Signed-off-by: Jyri Sarha <jsarha at ti.com>

Looks much cleaner to me.

Acked-by: Liviu Dudau <Liviu.Dudau at arm.com>

> ---
> 
> Ok, so this is the second approach to solve this issue. The first
> attempt can be found here [1] with the follow from Liviu Dudau that
> suggested this approach. 
> 
> It just makes me wonder if drm_atomic_helper_connector_dpms() should
> call the legacy callback automatically if DRIVER_ATOMIC is not set or
> at least bail out gracefully with an error message. Then again it may
> be overkill if the tda998x is the only driver that need to support
> both situations.

I would guess that in general it makes sense for the core code to do what
you suggest, but the idea is to try to encourage the drivers to convert
to atomic ops rather than give them too many crutches. And the tda998x will
need this for a short period of time until tilcdc converts as well.

Best regards,
Liviu

> 
> Best regards,
> Jyri
> 
> [1] http://www.spinics.net/lists/dri-devel/msg98514.html
> 
>  drivers/gpu/drm/i2c/tda998x_drv.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i2c/tda998x_drv.c b/drivers/gpu/drm/i2c/tda998x_drv.c
> index 012d36d..bb7d507 100644
> --- a/drivers/gpu/drm/i2c/tda998x_drv.c
> +++ b/drivers/gpu/drm/i2c/tda998x_drv.c
> @@ -1382,8 +1382,16 @@ static void tda998x_connector_destroy(struct drm_connector *connector)
>  	drm_connector_cleanup(connector);
>  }
>  
> +static int tda998x_connector_dpms(struct drm_connector *connector, int mode)
> +{
> +	if (drm_core_check_feature(connector->dev, DRIVER_ATOMIC))
> +		return drm_atomic_helper_connector_dpms(connector, mode);
> +	else
> +		return drm_helper_connector_dpms(connector, mode);
> +}
> +
>  static const struct drm_connector_funcs tda998x_connector_funcs = {
> -	.dpms = drm_atomic_helper_connector_dpms,
> +	.dpms = tda998x_connector_dpms,
>  	.reset = drm_atomic_helper_connector_reset,
>  	.fill_modes = drm_helper_probe_single_connector_modes,
>  	.detect = tda998x_connector_detect,
> -- 
> 1.9.1
> 

-- 
====================
| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
  ---------------
    ¯\_(ツ)_/¯