Re: [PATCH v4l-utils] Introduce v4l2-get-device tool

[Ezequiel Garcia <ezequiel@collabora.com>]

On Sat, 2018-11-10 at 11:29 +0100, Hans Verkuil wrote:
> On 11/09/2018 10:52 PM, Ezequiel Garcia wrote:
> > This tool allows to find a device by driver name,
> > this is useful for scripts to be written in a generic way.
> 
> Why not add support for this to v4l2-sysfs-path? And improve it at the same
> time (swradio devices do not show up when I run v4l2-sysfs-path, I also suspect
> v4l-touch devices aren't recognized. Ditto for media devices.
> 

I can add the functionality to v4l2-sysfs-path, and we can document
the rest in some TODO list, as I don't think we need to get everything
solved right now :-)

> > Usage:
> > 
> > v4l2-get-device -d uvcvideo -c V4L2_CAP_VIDEO_CAPTURE
> > /dev/video0
> > /dev/video2
> > 
> > Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
> > ---
> >  configure.ac                            |   1 +
> >  utils/Makefile.am                       |   1 +
> >  utils/v4l2-get-device/.gitignore        |   1 +
> >  utils/v4l2-get-device/Makefile.am       |   4 +
> >  utils/v4l2-get-device/v4l2-get-device.c | 147 ++++++++++++++++++++++++
> >  v4l-utils.spec.in                       |   1 +
> >  6 files changed, 155 insertions(+)
> >  create mode 100644 utils/v4l2-get-device/.gitignore
> >  create mode 100644 utils/v4l2-get-device/Makefile.am
> >  create mode 100644 utils/v4l2-get-device/v4l2-get-device.c
> > 
> > diff --git a/configure.ac b/configure.ac
> > index 5cc34c248fbf..918cb59704b9 100644
> > --- a/configure.ac
> > +++ b/configure.ac
> > @@ -31,6 +31,7 @@ AC_CONFIG_FILES([Makefile
> >  	utils/v4l2-compliance/Makefile
> >  	utils/v4l2-ctl/Makefile
> >  	utils/v4l2-dbg/Makefile
> > +	utils/v4l2-get-device/Makefile
> >  	utils/v4l2-sysfs-path/Makefile
> >  	utils/qv4l2/Makefile
> >  	utils/cec-ctl/Makefile
> > diff --git a/utils/Makefile.am b/utils/Makefile.am
> > index 2d5070288c13..2b2b27107d13 100644
> > --- a/utils/Makefile.am
> > +++ b/utils/Makefile.am
> > @@ -9,6 +9,7 @@ SUBDIRS = \
> >  	v4l2-compliance \
> >  	v4l2-ctl \
> >  	v4l2-dbg \
> > +	v4l2-get-device \
> >  	v4l2-sysfs-path \
> >  	cec-ctl \
> >  	cec-compliance \
> > diff --git a/utils/v4l2-get-device/.gitignore b/utils/v4l2-get-device/.gitignore
> > new file mode 100644
> > index 000000000000..b222144c9f4e
> > --- /dev/null
> > +++ b/utils/v4l2-get-device/.gitignore
> > @@ -0,0 +1 @@
> > +v4l2-get-device
> > diff --git a/utils/v4l2-get-device/Makefile.am b/utils/v4l2-get-device/Makefile.am
> > new file mode 100644
> > index 000000000000..2e5a6e0ba32f
> > --- /dev/null
> > +++ b/utils/v4l2-get-device/Makefile.am
> > @@ -0,0 +1,4 @@
> > +bin_PROGRAMS = v4l2-get-device
> > +v4l2_get_device_SOURCES = v4l2-get-device.c
> > +v4l2_get_device_LDADD = ../libmedia_dev/libmedia_dev.la
> > +v4l2_get_device_LDFLAGS = $(ARGP_LIBS)
> > diff --git a/utils/v4l2-get-device/v4l2-get-device.c b/utils/v4l2-get-device/v4l2-get-device.c
> > new file mode 100644
> > index 000000000000..f9cc323b7057
> > --- /dev/null
> > +++ b/utils/v4l2-get-device/v4l2-get-device.c
> > @@ -0,0 +1,147 @@
> > +/*
> > + * Copyright © 2018 Collabora, Ltd.
> > + *
> > + * Based on v4l2-sysfs-path by Mauro Carvalho Chehab:
> > + *
> > + * Copyright © 2011 Red Hat, Inc.
> > + *
> > + * Permission to use, copy, modify, distribute, and sell this software
> > + * and its documentation for any purpose is hereby granted without
> > + * fee, provided that the above copyright notice appear in all copies
> > + * and that both that copyright notice and this permission notice
> > + * appear in supporting documentation, and that the name of Red Hat
> > + * not be used in advertising or publicity pertaining to distribution
> > + * of the software without specific, written prior permission.  Red
> > + * Hat makes no representations about the suitability of this software
> > + * for any purpose.  It is provided "as is" without express or implied
> > + * warranty.
> > + *
> > + * THE AUTHORS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
> > + * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN
> > + * NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
> > + * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
> > + * OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
> > + * NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
> > + * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
> > + *
> > + */
> > +
> > +#include <argp.h>
> > +#include <config.h>
> > +#include <fcntl.h>
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +#include <string.h>
> > +#include <sys/types.h>
> > +#include <sys/stat.h>
> > +#include <sys/ioctl.h>
> > +#include <sys/unistd.h>
> > +
> > +#include <linux/videodev2.h>
> > +
> > +#include "../libmedia_dev/get_media_devices.h"
> > +
> > +const char *argp_program_version = "v4l2-get-device " V4L_UTILS_VERSION;
> > +const char *argp_program_bug_address = "Ezequiel Garcia <ezequiel@collabora.com>";
> > +
> > +struct args {
> > +	const char *driver;
> > +	unsigned int device_caps;
> > +};
> > +
> > +static const struct argp_option options[] = {
> > +	{"driver", 'd', "DRIVER", 0, "device driver name", 0},
> > +	{"v4l2-device-caps", 'c', "CAPS", 0, "v4l2 device capabilities", 0},
> 
> I'd like a bus-info option as well, if possible.
> 

Guess that works.

> > +	{ 0 }
> > +};
> > +
> > +static unsigned int parse_capabilities(const char *arg)
> > +{
> > +	char *s, *str = strdup(arg);
> > +	unsigned int caps = 0;
> > +
> > +	s = strtok (str,",");
> > +	while (s != NULL) {
> > +		if (!strcmp(s, "V4L2_CAP_VIDEO_CAPTURE"))
> > +			caps |= V4L2_CAP_VIDEO_CAPTURE;
> > +		else if (!strcmp(s, "V4L2_CAP_VIDEO_OUTPUT"))
> > +			caps |= V4L2_CAP_VIDEO_OUTPUT;
> > +		else if (!strcmp(s, "V4L2_CAP_VIDEO_OVERLAY"))
> > +			caps |= V4L2_CAP_VIDEO_OVERLAY;
> > +		else if (!strcmp(s, "V4L2_CAP_VBI_CAPTURE"))
> > +			caps |= V4L2_CAP_VBI_CAPTURE;
> > +		else if (!strcmp(s, "V4L2_CAP_VBI_OUTPUT"))
> > +			caps |= V4L2_CAP_VBI_OUTPUT;
> 
> Let's support all CAPS here. I'd also drop the V4L2_CAP_ prefix (or make it optional)
> and make the strcmp case-insensitive to ease typing.
> 

OK.

> > +		s = strtok (NULL, ",");
> > +	}
> > +	free(str);
> > +	return caps;
> > +}
> > +
> > +static error_t parse_opt(int k, char *arg, struct argp_state *state)
> > +{
> > +	struct args *args = state->input;
> > +
> > +	switch (k) {
> > +	case 'd':
> > +		args->driver = arg;
> > +		break;
> > +	case 'c':
> > +		args->device_caps = parse_capabilities(arg);
> > +		break;
> > +	default:
> > +		return ARGP_ERR_UNKNOWN;
> > +	}
> > +	return 0;
> > +}
> > +
> > +static struct argp argp = {
> > +	.options = options,
> > +	.parser = parse_opt,
> > +};
> > +
> > +int main(int argc, char *argv[])
> > +{
> > +	const char *vid;
> > +	struct args args;
> > +	void *md;
> > +
> > +	args.driver = NULL;
> > +	args.device_caps = 0;
> > +	argp_parse(&argp, argc, argv, 0, 0, &args);
> > +
> > +	md = discover_media_devices();
> 
> I never really liked this. My main problem is that it doesn't know about media devices.
> 

Sorry, not sure what you don't really like?

The discover_media_devices() is maybe not the best API, but it's what v4l2-sysfs-path
uses, and it seemed to fit what we need as a first step (to find v4l2 devices).

Perhaps we can use this for now and pospone improving the discovery library?

> In my view it should look for media devices first, query them and get all the device
> nodes referenced in the topology, and then fall back to the old method to discover
> any remaining device nodes for drivers that do not create a media device.
> 
> You need media device support anyway since you also want to be able to query the media
> device for a specific driver and find the device node for a specific entity.
> 

I've been thinking about this (since I started with http://git.ideasonboard.org/media-enum.git),
but to be honest, I failed to see why I would want to query media devices.

Let's say we want to find a H264 decoder, I don't think the topology is be
of much use, is it?

In any case, I think this is part of a bigger discussion, would you consider merging
v4l discovery for now?
 
> > +
> > +	vid = NULL;
> > +	do {
> > +		struct v4l2_capability cap;
> > +		char devnode[64];
> > +		int ret;
> > +		int fd;
> > +
> > +		vid = get_associated_device(md, vid, MEDIA_V4L_VIDEO,
> > +					    NULL, NONE);
> > +		if (!vid)
> > +			break;
> > +		snprintf(devnode, 64, "/dev/%s", vid);
> > +		fd = open(devnode, O_RDWR);
> > +		if (fd < 0)
> > +			continue;
> > +
> > +		memset(&cap, 0, sizeof cap);
> > +		ret = ioctl(fd, VIDIOC_QUERYCAP, &cap);
> > +		if (ret) {
> > +			close(fd);
> > +			continue;
> > +		}
> > +		close(fd);
> > +
> > +		if (strncmp(args.driver, (char *)cap.driver, sizeof(cap.driver)))
> > +			continue;
> > +		if (args.device_caps && (args.device_caps & cap.device_caps) != args.device_caps)
> > +			continue;
> > +		fprintf(stdout, "%s\n", devnode);
> > +	} while (vid);
> > +	free_media_devices(md);
> > +	return 0;
> > +}
> > diff --git a/v4l-utils.spec.in b/v4l-utils.spec.in
> > index 67bdca57ae92..ab15286b039b 100644
> > --- a/v4l-utils.spec.in
> > +++ b/v4l-utils.spec.in
> > @@ -159,6 +159,7 @@ gtk-update-icon-cache %{_datadir}/icons/hicolor &>/dev/null || :
> >  %{_bindir}/ivtv-ctl
> >  %{_bindir}/v4l2-ctl
> >  %{_bindir}/v4l2-sysfs-path
> > +%{_bindir}/v4l2-get-device
> >  %{_mandir}/man1/ir-keytable.1*
> >  %{_mandir}/man1/ir-ctl.1*
> >  
> > 
> 
> Regards,
> 
> 	Hans