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Date: Sat, 27 Jul 2013 15:07:00 +0200
From: David Herrmann <dh.herrmann@...il.com>
To: Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc: Dmitry Torokhov <dmitry.torokhov@...il.com>,
Benjamin Tissoires <benjamin.tissoires@...il.com>,
Peter Hutterer <peter.hutterer@...-t.net>,
"open list:HID CORE LAYER" <linux-input@...r.kernel.org>,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] input/uinput: add UI_GET_SYSPATH ioctl to retrieve
the sysfs path
Hi
On Mon, Jul 15, 2013 at 3:37 PM, Benjamin Tissoires
<benjamin.tissoires@...hat.com> wrote:
> Evemu [1] uses uinput to replay devices traces it has recorded. However,
> the way evemu uses uinput is slightly different from how uinput is
> supposed to be used.
> Evemu creates the device node through uinput, bu inject events through
> the input device node directly (and skipping the uinput node).
>
> Currently, evemu relies on an heuristic to guess which input node was
> created. The problem is that is heuristic is subjected to races between
> different uinput devices or even with physical devices. Having a way
> to retrieve the sysfs path allows us to find the event node without
> having to rely on this heuristic.
It would actually be enough to return the "input_no" from
input_register_device() (which is currently local but we could save it
in "dev"). Or only the device-name. I don't know why you want the full
syspath. It's just overhead in the kernel that we could easily let
user-space do. And the path /sys/class/input/<devname> can be put
together by user-space.
Anyway, Dmitry has to decide on that. Apart from some style-issues I
mentioned below:
Reviewed-by: David Herrmann <dh.herrmann@...il.com>
Cheers
David
> [1] http://www.freedesktop.org/wiki/Evemu/
>
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
> ---
> drivers/input/misc/uinput.c | 37 ++++++++++++++++++++++++++++++++++++-
> include/linux/uinput.h | 1 +
> include/uapi/linux/uinput.h | 3 +++
> 3 files changed, 40 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/input/misc/uinput.c b/drivers/input/misc/uinput.c
> index 7d518b4..49a9f7d 100644
> --- a/drivers/input/misc/uinput.c
> +++ b/drivers/input/misc/uinput.c
> @@ -22,6 +22,7 @@
> * Changes/Revisions:
> * 0.4 12/07/2013 (Peter Hutterer <peter.hutterer@...hat.com>)
> * - update uinput_user_dev struct to allow abs resolution
> + * - add UI_GET_SYSPATH ioctl
What tree is that patch against? I cannot see an "0.4" entry in:
http://git.kernel.org/cgit/linux/kernel/git/dtor/input.git/tree/drivers/input/misc/uinput.c?h=next
> * 0.3 09/04/2006 (Anssi Hannula <anssi.hannula@...il.com>)
> * - updated ff support for the changes in kernel interface
> * - added MODULE_VERSION
> @@ -667,6 +668,21 @@ static int uinput_ff_upload_from_user(const char __user *buffer,
> __ret; \
> })
>
> +static int uinput_str_to_user(const char *str, unsigned int maxlen,
> + void __user *p)
As Peter mentioned, I'd move "maxlen" to the end.
> +{
> + int len;
> +
> + if (!str)
> + return -ENOENT;
> +
> + len = strlen(str) + 1;
> + if (len > maxlen)
> + len = maxlen;
> +
> + return copy_to_user(p, str, len) ? -EFAULT : len;
I'd prefer a "strlcpy()" so we guarantee a terminating 0 for
user-space, but I guess that'd be rather complex to do here. I
couldn't find any strlcpy_to_user()...
> +}
> +
> static long uinput_ioctl_handler(struct file *file, unsigned int cmd,
> unsigned long arg, void __user *p)
> {
> @@ -676,6 +692,8 @@ static long uinput_ioctl_handler(struct file *file, unsigned int cmd,
> struct uinput_ff_erase ff_erase;
> struct uinput_request *req;
> char *phys;
> + const char *path;
> + unsigned int size;
>
> retval = mutex_lock_interruptible(&udev->mutex);
> if (retval)
> @@ -828,7 +846,24 @@ static long uinput_ioctl_handler(struct file *file, unsigned int cmd,
> break;
>
> default:
> - retval = -EINVAL;
> + retval = -EAGAIN;
> + }
> +
> + if (retval == -EAGAIN) {
> + size = _IOC_SIZE(cmd);
> +
> + /* Now check variable-length commands */
> + switch (cmd & ~IOCSIZE_MASK) {
> + case UI_GET_SYSPATH(0):
> + path = kobject_get_path(&udev->dev->dev.kobj,
> + GFP_KERNEL);
I know, device registration is protected by udev->mutex but I'd still prefer:
if (udev->state != UIST_CREATED)
return -ENOENT;
But that's probably a matter of taste.
> + retval = uinput_str_to_user(path, size, p);
> + kfree(path);
> + break;
> +
> + default:
> + retval = -EINVAL;
> + }
> }
>
> out:
> diff --git a/include/linux/uinput.h b/include/linux/uinput.h
> index 6291a22..64fab81 100644
> --- a/include/linux/uinput.h
> +++ b/include/linux/uinput.h
> @@ -22,6 +22,7 @@
> * Changes/Revisions:
> * 0.4 12/07/2013 (Peter Hutterer <peter.hutterer@...hat.com>)
> * - update uinput_user_dev struct to allow abs resolution
> + * - add UI_GET_SYSPATH ioctl
> * 0.3 24/05/2006 (Anssi Hannula <anssi.hannulagmail.com>)
> * - update ff support for the changes in kernel interface
> * - add UINPUT_VERSION
> diff --git a/include/uapi/linux/uinput.h b/include/uapi/linux/uinput.h
> index f6a393b..d826409 100644
> --- a/include/uapi/linux/uinput.h
> +++ b/include/uapi/linux/uinput.h
> @@ -22,6 +22,7 @@
> * Changes/Revisions:
> * 0.4 12/07/2013 (Peter Hutterer <peter.hutterer@...hat.com>)
> * - update uinput_user_dev struct to allow abs resolution
> + * - add UI_GET_SYSPATH ioctl
> * 0.3 24/05/2006 (Anssi Hannula <anssi.hannulagmail.com>)
> * - update ff support for the changes in kernel interface
> * - add UINPUT_VERSION
> @@ -75,6 +76,8 @@ struct uinput_ff_erase {
> #define UI_BEGIN_FF_ERASE _IOWR(UINPUT_IOCTL_BASE, 202, struct uinput_ff_erase)
> #define UI_END_FF_ERASE _IOW(UINPUT_IOCTL_BASE, 203, struct uinput_ff_erase)
>
> +#define UI_GET_SYSPATH(len) _IOC(_IOC_READ, UINPUT_IOCTL_BASE, 300, len)
> +
> /*
> * To write a force-feedback-capable driver, the upload_effect
> * and erase_effect callbacks in input_dev must be implemented.
> --
> 1.8.3.1
>
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