linux-kernel - Re: [PATCH 1/3 v4] drm: Introduce drm_connector_register

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Message-ID: <1459246208.3021.15.camel@synopsys.com>
Date:	Tue, 29 Mar 2016 10:10:08 +0000
From:	Alexey Brodkin <Alexey.Brodkin@...opsys.com>
To:	"dh.herrmann@...il.com" <dh.herrmann@...il.com>
CC:	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"daniel@...ll.ch" <daniel@...ll.ch>,
	"airlied@...ux.ie" <airlied@...ux.ie>
Subject: Re: [PATCH 1/3 v4] drm: Introduce drm_connector_register_all()
 helper

Hi David,

On Tue, 2016-03-29 at 12:08 +0200, David Herrmann wrote:
> Hi
> 
> On Tue, Mar 29, 2016 at 12:02 PM, Alexey Brodkin
> <Alexey.Brodkin@...opsys.com> wrote:
> > 
> > As a pair to already existing drm_connector_unregister_all() we're adding
> > generic implementation of what is already done in some drivers.
> > 
> > Once this helper is implemented we'll be ready to switch existing
> > driver-specific implementations with the generic one.
> > 
> > Signed-off-by: Alexey Brodkin <abrodkin@...opsys.com>
> > Cc: Daniel Vetter <daniel@...ll.ch>
> > Cc: David Airlie <airlied@...ux.ie>
> > Cc: David Herrmann <dh.herrmann@...il.com>
> > ---
> > 
> > Changes v3 -> v4:
> >  * In drm_connector_register_all() fail path which calls unregister_all()
> >    is moved outside of loop&locked section (as suggested by Daniel)
> > 
> > Changes v2 -> v3:
> >  * Updated title with capital after colon
> >  * Simplified failure path with direct and unconditional invocation of
> >    unregister_all()
> >  * Updated kerneldoc description of the drm_connector_register_all()
> > 
> > Changes v1 -> v2:
> >  * Rename drm_connector_unplug_all() to drm_connector_unregister_all()
> >  * Use drm_for_each_connector() instead of list_for_each_entry()
> >  * Updated kerneldoc for drm_dev_register()
> > 
> >  drivers/gpu/drm/drm_crtc.c | 39 +++++++++++++++++++++++++++++++++++++++
> >  drivers/gpu/drm/drm_drv.c  |  6 +++++-
> >  include/drm/drm_crtc.h     |  3 ++-
> >  3 files changed, 46 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> > index 7675826..3e4cdb1 100644
> > --- a/drivers/gpu/drm/drm_crtc.c
> > +++ b/drivers/gpu/drm/drm_crtc.c
> > @@ -1079,6 +1079,45 @@ void drm_connector_unregister(struct drm_connector *connector)
> >  EXPORT_SYMBOL(drm_connector_unregister);
> > 
> >  /**
> > + * drm_connector_register_all - register all connectors
> > + * @dev: drm device
> > + *
> > + * This function registers all connectors in sysfs and other places so that
> > + * userspace can start to access them. Drivers can call it after calling
> > + * drm_dev_register() to complete the device registration, if they don't call
> > + * drm_connector_register() on each connector individually.
> > + *
> > + * When a device is unplugged and should be removed from userspace access,
> > + * call drm_connector_unregister_all(), which is the inverse of this
> > + * function.
> > + *
> > + * Returns:
> > + * Zero on success, error code on failure.
> > + */
> > +int drm_connector_register_all(struct drm_device *dev)
> > +{
> > +       struct drm_connector *connector;
> > +       int ret;
> > +
> > +       mutex_lock(&dev->mode_config.mutex);
> > +
> > +       drm_for_each_connector(connector, dev) {
> > +               ret = drm_connector_register(connector);
> > +               if (ret)
> > +                       goto err;
> > +       }
> > +
> > +       mutex_unlock(&dev->mode_config.mutex);
> > +
> > +       return 0;
> > +
> > +err:
> > +       drm_connector_unregister_all(dev);
> You _must_ unlock the mutex before returning.

So true!

BTW that's why I liked the previous solution - code was much cleaner
with only 1 branch of execution.

Will resend v5 in a minute.

-Alexey