Re: [PATCH v3] input/uinput: add UI_GET_SYSNAME ioctl to retrieve thesysfs path
From: Benjamin Tissoires
Date: Mon Jan 20 2014 - 13:59:55 EST
Hi David,
thanks for the review
On Sat, Jan 18, 2014 at 5:51 AM, David Herrmann <dh.herrmann@xxxxxxxxx> wrote:
> Hi
>
> On Fri, Jan 17, 2014 at 8:12 PM, Benjamin Tissoires
> <benjamin.tissoires@xxxxxxxxxx> 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 relies on libevdev, which creates the device node through uinput.
>> It then injects events through the input device node directly (and it
>> completely skips the uinput node).
>>
>> Currently, libevdev 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.
>>
>> [1] http://www.freedesktop.org/wiki/Evemu/
>>
>> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
>> ---
>>
>> Ok, I am resurrecting this. The original patch was sent last July here:
>> https://patchwork.kernel.org/patch/2827524/
>>
>> changes since v2:
>> - the ioctl returns only the device name, thus I renamed the ioctl to UI_GET_SYSNAME
>> - reordered uinput_str_to_user() arguments
>> - be sure to terminate the user string we send by \0
>> - abort if udev->state is not UIST_CREATED
>> - dropped the patch 1/2 (adding resolution to uinput) because I think David has
>> already it in one of his queues (ABS2 IIRC)
>>
>> I also posted the corresponding libevdev here:
>> http://lists.freedesktop.org/archives/input-tools/2014-January/000757.html
>>
>> Cheers,
>> Benjamin
>>
>> drivers/input/misc/uinput.c | 46 ++++++++++++++++++++++++++++++++++++++++++++-
>> include/linux/uinput.h | 2 ++
>> include/uapi/linux/uinput.h | 13 ++++++++++++-
>> 3 files changed, 59 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/input/misc/uinput.c b/drivers/input/misc/uinput.c
>> index 7728359..0203219 100644
>> --- a/drivers/input/misc/uinput.c
>> +++ b/drivers/input/misc/uinput.c
>> @@ -20,6 +20,8 @@
>> * Author: Aristeu Sergio Rozanski Filho <aris@xxxxxxxxxxxxxxxxx>
>> *
>> * Changes/Revisions:
>> + * 0.4 01/09/2014 (Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>)
>> + * - add UI_GET_SYSNAME ioctl
>> * 0.3 09/04/2006 (Anssi Hannula <anssi.hannula@xxxxxxxxx>)
>> * - updated ff support for the changes in kernel interface
>> * - added MODULE_VERSION
>> @@ -670,6 +672,27 @@ static int uinput_ff_upload_from_user(const char __user *buffer,
>> __ret; \
>> })
>>
>> +static int uinput_str_to_user(void __user *dest, const char *str,
>> + unsigned int maxlen)
>> +{
>> + int len, ret;
>> +
>> + if (!str)
>> + return -ENOENT;
>> +
>> + len = strlen(str) + 1;
>> + if (len > maxlen)
>> + len = maxlen;
>> +
>> + ret = copy_to_user(dest, str, len);
>> + if (ret)
>> + return -EFAULT;
>> +
>> + /* force terminating '\0' */
>> + ret = copy_to_user(dest + len - 1, "\0", 1);
>
> You must make sure "maxlen != 0", otherwise you write beyond buffer
> boundaries here. I'd say return -EINVAL in case maxlen == 0.
oh, yes, you are right.
>
> btw., you can also use: put_user(0, (char*)dest + len - 1);
k, will amend
>
>> + return ret ? -EFAULT : len;
>> +}
>> +
>> static long uinput_ioctl_handler(struct file *file, unsigned int cmd,
>> unsigned long arg, void __user *p)
>> {
>> @@ -679,6 +702,8 @@ 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 *name;
>> + unsigned int size;
>>
>> retval = mutex_lock_interruptible(&udev->mutex);
>> if (retval)
>> @@ -831,7 +856,26 @@ static long uinput_ioctl_handler(struct file *file, unsigned int cmd,
>> break;
>>
>> default:
>> - retval = -EINVAL;
>> + retval = -EAGAIN;
>> + }
>> +
>> + if (retval == -EAGAIN) {
>
> Ehh, in case another ioctl returns -EAGAIN, we overwrite the error
> with -EINVAL below in the "default:" clause. Maybe we should first
> convert all the "break;" commands to "goto out;".
yep, that was one of the thing which also made me some trouble by
re-reading the patch after this amount of time.
Either I can make a "goto out" patch before, or I can just add a bool
probe_variable_length which would be set be the previous default case.
The latter implies less changes, but might be more ugly than the previous.
Any preferences?
>
> Patch looks good to me.
Thanks!
Cheers,
Benjamin
> Thanks
> David
>
>> + size = _IOC_SIZE(cmd);
>> +
>> + /* Now check variable-length commands */
>> + switch (cmd & ~IOCSIZE_MASK) {
>> + case UI_GET_SYSNAME(0):
>> + if (udev->state != UIST_CREATED) {
>> + retval = -ENOENT;
>> + goto out;
>> + }
>> + name = dev_name(&udev->dev->dev);
>> + retval = uinput_str_to_user(p, name, size);
>> + break;
>> +
>> + default:
>> + retval = -EINVAL;
>> + }
>> }
>>
>> out:
>> diff --git a/include/linux/uinput.h b/include/linux/uinput.h
>> index 0a4487d..0994c0d 100644
>> --- a/include/linux/uinput.h
>> +++ b/include/linux/uinput.h
>> @@ -20,6 +20,8 @@
>> * Author: Aristeu Sergio Rozanski Filho <aris@xxxxxxxxxxxxxxxxx>
>> *
>> * Changes/Revisions:
>> + * 0.4 01/09/2014 (Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>)
>> + * - add UI_GET_SYSNAME 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 fe46431..0389b48 100644
>> --- a/include/uapi/linux/uinput.h
>> +++ b/include/uapi/linux/uinput.h
>> @@ -20,6 +20,8 @@
>> * Author: Aristeu Sergio Rozanski Filho <aris@xxxxxxxxxxxxxxxxx>
>> *
>> * Changes/Revisions:
>> + * 0.4 01/09/2014 (Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>)
>> + * - add UI_GET_SYSNAME ioctl
>> * 0.3 24/05/2006 (Anssi Hannula <anssi.hannulagmail.com>)
>> * - update ff support for the changes in kernel interface
>> * - add UINPUT_VERSION
>> @@ -35,7 +37,7 @@
>> #include <linux/types.h>
>> #include <linux/input.h>
>>
>> -#define UINPUT_VERSION 3
>> +#define UINPUT_VERSION 4
>>
>>
>> struct uinput_ff_upload {
>> @@ -73,6 +75,15 @@ 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)
>>
>> +/**
>> + * UI_GET_SYSNAME - get the sysfs name of the created uinput device
>> + *
>> + * @return the sysfs name of the created virtual input device.
>> + * The complete sysfs path is then /sys/devices/virtual/input/--NAME--
>> + * Usually, it is in the form "inputN"
>> + */
>> +#define UI_GET_SYSNAME(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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