Hi Sylwester
On Mon, 8 Apr 2013, Sylwester Nawrocki wrote:
> Hi Guennadi,
>
> On 04/08/2013 01:07 PM, Guennadi Liakhovetski wrote:
> > Currently bridge device drivers register devices for all subdevices
> > synchronously, tupically, during their probing. E.g. if an I2C CMOS sensor
> > is attached to a video bridge device, the bridge driver will create an I2C
> > device and wait for the respective I2C driver to probe. This makes linking
> > of devices straight forward, but this approach cannot be used with
> > intrinsically asynchronous and unordered device registration systems like
> > the Flattened Device Tree. To support such systems this patch adds an
> > asynchronous subdevice registration framework to V4L2. To use it respective
> > (e.g. I2C) subdevice drivers must register themselves with the framework.
> > A bridge driver on the other hand must register notification callbacks,
> > that will be called upon various related events.
> >
> > Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@xxxxxx>
> > ---
> >
> > v7:
> > 1. Removed bogus device reprobing from v4l2_async_unregister_subdev()
> > 2. Renamed V4L2_ASYNC_BUS_SPECIAL to V4L2_ASYNC_BUS_CUSTOM
>
> This change seems to be missing.
Indeed :-(
> > 3. Renamed v4l2_async_subdev_(un)register() to v4l2_async_(un)register_subdev()
[snip]
> > +static struct v4l2_async_subdev *v4l2_async_belongs(struct v4l2_async_notifier *notifier,
> > + struct v4l2_async_subdev_list *asdl)
> > +{
> > + struct v4l2_async_subdev *asd = NULL;
> > + bool (*match)(struct device *,
> > + struct v4l2_async_hw_device *);
> > +
> > + list_for_each_entry (asd, ¬ifier->waiting, list) {
> > + struct v4l2_async_hw_device *hw = &asd->hw;
> > + switch (hw->bus_type) {
> > + case V4L2_ASYNC_BUS_SPECIAL:
> > + match = hw->match.special.match;
> > + if (!match)
> > + /* Match always */
> > + return asd;
> > + break;
> > + case V4L2_ASYNC_BUS_PLATFORM:
> > + match = match_platform;
> > + break;
> > + case V4L2_ASYNC_BUS_I2C:
> > + match = match_i2c;
> > + break;
> > + default:
> > + /* Oops */
> > + match = NULL;
> > + dev_err(notifier->v4l2_dev ? notifier->v4l2_dev->dev : NULL,
> > + "Invalid bus-type %u on %p\n", hw->bus_type, asd);
> > + }
> > +
> > + if (match && match(asdl->dev, hw))
> > + break;
>
> Since we maintain various lists of sub-devices, couldn't we match them e.g. by
> name instead ? What would be preventing this ?
Do you have a specific case where your proposal would work, whereas mine
wouldn't? This can be changed at any time, we can leave it until there's a
real use-case, for which this implementation wouldn't work.
> And additionally provide an API to override the matching method?
Override - that's what the "SPECIAL" (CUSTOM) is for.
> > diff --git a/include/media/v4l2-async.h b/include/media/v4l2-async.h
> > new file mode 100644
> > index 0000000..c0470c6
> > --- /dev/null
> > +++ b/include/media/v4l2-async.h
> > @@ -0,0 +1,105 @@
> > +/*
> > + * V4L2 asynchronous subdevice registration API
> > + *
> > + * Copyright (C) 2012, Guennadi Liakhovetski <g.liakhovetski@xxxxxx>
>
> s/2012/2013 ?
>
> > + *
> > + * This program is free software; you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License version 2 as
> > + * published by the Free Software Foundation.
> > + */
> > +
> > +#ifndef V4L2_ASYNC_H
> > +#define V4L2_ASYNC_H
> > +
> > +#include <linux/list.h>
> > +#include <linux/mutex.h>
> > +#include <linux/notifier.h>
>
> Is there anything used from this header ?
Don't think so, I'll remove it.
Thanks
Guennadi
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/
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