linux-kernel - Re: [PATCH v2 1/6] drm/vkms: Switch to managed for connector

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Message-ID: <20240827-tactful-delectable-stork-06bded@houat>
Date: Tue, 27 Aug 2024 18:42:18 +0200
From: Maxime Ripard <mripard@...nel.org>
To: Rodrigo Siqueira <rodrigosiqueiramelo@...il.com>, 
	Melissa Wen <melissa.srw@...il.com>, Maíra Canal <mairacanal@...eup.net>, 
	Haneen Mohammed <hamohammed.sa@...il.com>, Daniel Vetter <daniel@...ll.ch>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Thomas Zimmermann <tzimmermann@...e.de>, 
	David Airlie <airlied@...il.com>, dri-devel@...ts.freedesktop.org, arthurgrillo@...eup.net, 
	linux-kernel@...r.kernel.org, jeremie.dautheribes@...tlin.com, miquel.raynal@...tlin.com, 
	thomas.petazzoni@...tlin.com, seanpaul@...gle.com, nicolejadeyee@...gle.com
Subject: Re: [PATCH v2 1/6] drm/vkms: Switch to managed for connector

On Tue, Aug 27, 2024 at 05:08:08PM GMT, Louis Chauvet wrote:
> Le 27/08/24 - 16:39, Maxime Ripard a écrit :
> > On Tue, Aug 27, 2024 at 03:24:10PM GMT, Louis Chauvet wrote:
> > > Le 27/08/24 - 15:15, Maxime Ripard a écrit :
> > > > Hi,
> > > > 
> > > > On Tue, Aug 27, 2024 at 11:57:36AM GMT, Louis Chauvet wrote:
> > > > > The current VKMS driver uses non-managed function to create connectors. It
> > > > > is not an issue yet, but in order to support multiple devices easily,
> > > > > convert this code to use drm and device managed helpers.
> > > > > 
> > > > > Signed-off-by: Louis Chauvet <louis.chauvet@...tlin.com>
> > > > > ---
> > > > >  drivers/gpu/drm/vkms/vkms_drv.h    |  1 -
> > > > >  drivers/gpu/drm/vkms/vkms_output.c | 22 ++++++++++++----------
> > > > >  2 files changed, 12 insertions(+), 11 deletions(-)
> > > > > 
> > > > > diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
> > > > > index 5e46ea5b96dc..9a3c6c34d1f6 100644
> > > > > --- a/drivers/gpu/drm/vkms/vkms_drv.h
> > > > > +++ b/drivers/gpu/drm/vkms/vkms_drv.h
> > > > > @@ -99,7 +99,6 @@ struct vkms_crtc_state {
> > > > >  struct vkms_output {
> > > > >  	struct drm_crtc crtc;
> > > > >  	struct drm_encoder encoder;
> > > > > -	struct drm_connector connector;
> > > > >  	struct drm_writeback_connector wb_connector;
> > > > >  	struct hrtimer vblank_hrtimer;
> > > > >  	ktime_t period_ns;
> > > > > diff --git a/drivers/gpu/drm/vkms/vkms_output.c b/drivers/gpu/drm/vkms/vkms_output.c
> > > > > index 5ce70dd946aa..4fe6b88e8081 100644
> > > > > --- a/drivers/gpu/drm/vkms/vkms_output.c
> > > > > +++ b/drivers/gpu/drm/vkms/vkms_output.c
> > > > > @@ -3,11 +3,11 @@
> > > > >  #include "vkms_drv.h"
> > > > >  #include <drm/drm_atomic_helper.h>
> > > > >  #include <drm/drm_edid.h>
> > > > > +#include <drm/drm_managed.h>
> > > > >  #include <drm/drm_probe_helper.h>
> > > > >  
> > > > >  static const struct drm_connector_funcs vkms_connector_funcs = {
> > > > >  	.fill_modes = drm_helper_probe_single_connector_modes,
> > > > > -	.destroy = drm_connector_cleanup,
> > > > >  	.reset = drm_atomic_helper_connector_reset,
> > > > >  	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
> > > > >  	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
> > > > > @@ -50,7 +50,7 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index)
> > > > >  {
> > > > >  	struct vkms_output *output = &vkmsdev->output;
> > > > >  	struct drm_device *dev = &vkmsdev->drm;
> > > > > -	struct drm_connector *connector = &output->connector;
> > > > > +	struct drm_connector *connector;
> > > > >  	struct drm_encoder *encoder = &output->encoder;
> > > > >  	struct drm_crtc *crtc = &output->crtc;
> > > > >  	struct vkms_plane *primary, *cursor = NULL;
> > > > > @@ -80,8 +80,15 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index)
> > > > >  	if (ret)
> > > > >  		return ret;
> > > > >  
> > > > > -	ret = drm_connector_init(dev, connector, &vkms_connector_funcs,
> > > > > -				 DRM_MODE_CONNECTOR_VIRTUAL);
> > > > > +	connector = drmm_kzalloc(dev, sizeof(*connector), GFP_KERNEL);
> > > > > +	if (!connector) {
> > > > > +		DRM_ERROR("Failed to allocate connector\n");
> > > > > +		ret = -ENOMEM;
> > > > > +		goto err_connector;
> > > > > +	}
> > > > > +
> > > > 
> > > > I think it would be worth explaining why you need to move to a separate
> > > > allocation for the connector now.
> > > > 
> > > > Maxime
> > > 
> > > Hi,
> > > 
> > > This is in preparation for ConfigFS implementation, as the number of 
> > > connector/encoders/crtc/planes... will be dynamic, we need to have 
> > > separate alloaction.
> > > 
> > > If I add this paragraph in the commit message, is it sufficient?
> > > 
> > > 	A specific allocation for the connector is not strictly necessary 
> > > 	at this point, but in order to implement dynamic configuration of 
> > > 	VKMS (configFS), it will be easier to have one allocation per 
> > > 	connector.
> > > 
> > > (same for encoder & CRTC)
> > 
> > Yeah, that's a good message, but it probably belongs in a separate patch
> > then.
> 
> Can you explain what you mean by "in a separate patch"? I wanted to write 
> this paragraph in the commit log.

You're doing two things in that patch: converting to drmm like you
documented in your original commit log, and switching from having the
connector (encoder, and crtc) from vkms_output to being dynamically
allocated.

Ideally, you should have one patch to switch from being part of
vkms_output to a dynamic allocation (with the commit log you suggested
above), and one patch to switch to drmm with your original commit log.

Maxime

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