[systemd-devel] [PATCH udev v4] udev: Add builtin/rule to export touchscreen/tablet size as udev properties

[David Herrmann]

Hi

On Mon, Dec 22, 2014 at 5:04 PM, Carlos Garnacho <carlosg at gnome.org> wrote:
> This rule is only run on tablet/touchscreen devices, and extracts their size
> in millimeters, as it can be found out through their struct input_absinfo.
>
> This may be useful to separate policy and application at the time of mapping
> these devices to the available outputs in windowing environments that don't
> offer that information as readily (eg. Wayland). This way the compositor can
> stay deterministic, and the mix-and-match heuristics are performed outside.
>
> Conceivably, that information can be changed through EVIOCSABS anywhere
> else, but we're only interested in values prior to any calibration, this
> rule is thus only run on "add", and no tracking of changes is performed.
> This should only remain a problem if calibration were automatically applied
> by an earlier udev rule (read: don't).
>
>   v2: Folded rationale into commit log, made a builtin, set properties
>       on device nodes themselves
>   v3: Use inline function instead of macro for mm. size calculation,
>       use DECIMAL_STR_MAX, other code style issues
>   v4: Made rule more selective
> ---
>  Makefile.am                            |  2 +
>  rules/60-input_abs_size.rules          |  9 ++++
>  src/udev/udev-builtin-input_abs_size.c | 81 ++++++++++++++++++++++++++++++++++
>  src/udev/udev-builtin.c                |  1 +
>  src/udev/udev.h                        |  2 +
>  5 files changed, 95 insertions(+)
>  create mode 100644 rules/60-input_abs_size.rules
>  create mode 100644 src/udev/udev-builtin-input_abs_size.c
>
> diff --git a/Makefile.am b/Makefile.am
> index ab07d3b..db3e014 100644
> --- a/Makefile.am
> +++ b/Makefile.am
> @@ -3412,6 +3412,7 @@ dist_udevrules_DATA += \
>         rules/42-usb-hid-pm.rules \
>         rules/50-udev-default.rules \
>         rules/60-drm.rules \
> +       rules/60-input_abs_size.rules \
>         rules/60-keyboard.rules \
>         rules/70-mouse.rules \
>         rules/60-persistent-storage-tape.rules \
> @@ -3512,6 +3513,7 @@ libudev_core_la_SOURCES = \
>         src/udev/udev-builtin.c \
>         src/udev/udev-builtin-btrfs.c \
>         src/udev/udev-builtin-hwdb.c \
> +       src/udev/udev-builtin-input_abs_size.c \
>         src/udev/udev-builtin-input_id.c \
>         src/udev/udev-builtin-keyboard.c \
>         src/udev/udev-builtin-net_id.c \
> diff --git a/rules/60-input_abs_size.rules b/rules/60-input_abs_size.rules
> new file mode 100644
> index 0000000..90c0eef
> --- /dev/null
> +++ b/rules/60-input_abs_size.rules
> @@ -0,0 +1,9 @@
> +# do not edit this file, it will be overwritten on update
> +
> +ACTION!="add", GOTO="input_abs_size_end"
> +KERNEL!="event*", GOTO="input_abs_size_end"

Please also match on the "input" subsystem here. There might be other
devices called "event<something>".

> +
> +ENV{ID_INPUT_TOUCHSCREEN}=="1", IMPORT{builtin}="input_abs_size"
> +ENV{ID_INPUT_TABLET}=="1", IMPORT{builtin}="input_abs_size"
> +
> +LABEL="input_abs_size_end"
> diff --git a/src/udev/udev-builtin-input_abs_size.c b/src/udev/udev-builtin-input_abs_size.c
> new file mode 100644
> index 0000000..faf707e
> --- /dev/null
> +++ b/src/udev/udev-builtin-input_abs_size.c
> @@ -0,0 +1,81 @@
> +/*
> + * input_abs_size - extracts abs X/Y size in millimeters from input devices
> + *
> + * Copyright (C) 2014 Red Hat
> + * Author:
> + *   Carlos Garnacho  <carlosg at gnome.org>
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful, but
> + * WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with keymap; if not, write to the Free Software Foundation,
> + * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
> + */
> +
> +#include <linux/input.h>
> +#include "udev.h"

Please include "util.h" directly, as you use quite a bunch of helpers from it.

> +
> +static inline int abs_size_mm(const struct input_absinfo *absinfo)
> +{

We put the opening-braces on the same line as the function.

> +        /* Resolution is defined to be in units/mm for ABS_X/Y */
> +        return (absinfo->maximum - absinfo->minimum) / absinfo->resolution;
> +}
> +
> +static void extract_info(struct udev_device *dev, const char *devpath, bool test)
> +{
> +        char width[DECIMAL_STR_MAX(int)], height[DECIMAL_STR_MAX(int)];
> +        struct input_absinfo xabsinfo = {}, yabsinfo = {};
> +        _cleanup_close_ int fd = -1;
> +
> +        fd = open(devpath, O_RDONLY|O_CLOEXEC);
> +

Drop that empty line.

> +        if (fd < 0)
> +                return;
> +
> +        if (ioctl(fd, EVIOCGABS(ABS_X), &xabsinfo) < 0 ||
> +            ioctl(fd, EVIOCGABS(ABS_Y), &yabsinfo) < 0)
> +                return;
> +
> +        if (xabsinfo.resolution <= 0 || yabsinfo.resolution <= 0)
> +                return;
> +
> +        snprintf(width, sizeof(width), "%d", abs_size_mm(&xabsinfo));
> +        snprintf(height, sizeof(height), "%d", abs_size_mm(&yabsinfo));
> +
> +        udev_builtin_add_property(dev, test, "ID_INPUT_WIDTH_MM", width);
> +        udev_builtin_add_property(dev, test, "ID_INPUT_HEIGHT_MM", height);
> +}
> +
> +static int builtin_input_abs_size(struct udev_device *dev, int argc, char *argv[], bool test) {
> +        const char *subsystem;
> +        const char *devnode;
> +
> +        subsystem = udev_device_get_subsystem(dev);
> +
> +        if (!subsystem || !streq(subsystem, "input"))
> +                return EXIT_SUCCESS;
> +
> +        devnode = udev_device_get_devnode(dev);
> +

Again, please drop that empty line.

> +        /* not an evdev node */
> +        if (!devnode)
> +                return EXIT_SUCCESS;
> +
> +        extract_info(dev, devnode, test);
> +
> +        return EXIT_SUCCESS;
> +}
> +
> +const struct udev_builtin udev_builtin_input_abs_size = {
> +        .name = "input_abs_size",
> +        .cmd = builtin_input_abs_size,
> +        .help = "input device size information",
> +};
> diff --git a/src/udev/udev-builtin.c b/src/udev/udev-builtin.c
> index 3bcbd6e..9febf4c 100644
> --- a/src/udev/udev-builtin.c
> +++ b/src/udev/udev-builtin.c
> @@ -47,6 +47,7 @@ static const struct udev_builtin *builtins[] = {
>  #ifdef HAVE_ACL
>          [UDEV_BUILTIN_UACCESS] = &udev_builtin_uaccess,
>  #endif
> +        [UDEV_BUILTIN_INPUT_ABS_SIZE] = &udev_builtin_input_abs_size,
>  };
>
>  void udev_builtin_init(struct udev *udev) {
> diff --git a/src/udev/udev.h b/src/udev/udev.h
> index dece6ec..d3b3b51 100644
> --- a/src/udev/udev.h
> +++ b/src/udev/udev.h
> @@ -164,6 +164,7 @@ enum udev_builtin_cmd {
>  #ifdef HAVE_ACL
>          UDEV_BUILTIN_UACCESS,
>  #endif
> +        UDEV_BUILTIN_INPUT_ABS_SIZE,
>          UDEV_BUILTIN_MAX
>  };
>  struct udev_builtin {
> @@ -190,6 +191,7 @@ extern const struct udev_builtin udev_builtin_net_setup_link;
>  extern const struct udev_builtin udev_builtin_path_id;
>  extern const struct udev_builtin udev_builtin_usb_id;
>  extern const struct udev_builtin udev_builtin_uaccess;
> +extern const struct udev_builtin udev_builtin_input_abs_size;
>  void udev_builtin_init(struct udev *udev);
>  void udev_builtin_exit(struct udev *udev);
>  enum udev_builtin_cmd udev_builtin_lookup(const char *command);

Otherwise, looks all good. I was about to push it, but could you
rename it to something more generic? "udev_builtin_evdev_id" for
example. I don't want a different builtin for each evdev property we
add, so lets be generic enough right from the beginning.

Thanks
David