linux-kernel - Re: [PATCH v2 1/1] Input: don't modify the id of ioctl-provided ff effect on upload failure

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Message-ID: <20140329191236.GC10710@core.coreip.homeip.net>
Date:	Sat, 29 Mar 2014 12:12:36 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Elias Vanderstuyft <elias.vds@...il.com>
Cc:	Anssi Hannula <anssi.hannula@....fi>,
	Michal Malý <madcatxster@...oid-pointer.net>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/1] Input: don't modify the id of ioctl-provided ff
 effect on upload failure

On Sat, Mar 29, 2014 at 01:16:36PM +0100, Elias Vanderstuyft wrote:
> If a new (id == -1) ff effect was uploaded from userspace,
> ff-core.c::input_ff_upload() will have assigned
> a positive number to the new effect id.
> Currently, evdev.c::evdev_do_ioctl() will save this new id to userspace,
> regardless of whether the upload succeeded or not.
> 
> On upload failure, this can be confusing because the dev->ff->effects[] array
> will not contain an element at the index of that new effect id.
> 
> This patch fixes this by leaving the id unchanged after upload fails.
> 
> Note: Unfortunately applications should still expect changed effect id for
> quite some time.
> 
> This has been discussed on:
> http://www.mail-archive.com/linux-input@vger.kernel.org/msg08513.html
> ("ff-core effect id handling in case of a failed effect upload")
> 
> Suggested-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
> Signed-off-by: Elias Vanderstuyft <elias.vds@...il.com>
> Cc: Anssi Hannula <anssi.hannula@....fi>
> Cc: Michal Malý <madcatxster@...oid-pointer.net>
> Cc: linux-input@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org

Applied, thank you, and sorry for the delay.

> ---
>  v2:
>   Only added one line to the commit message to say
>   what this patch actually does,
>   instead of only stating the reason why it's submitted.
> 
>  drivers/input/evdev.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
> index a06e125..ce953d8 100644
> --- a/drivers/input/evdev.c
> +++ b/drivers/input/evdev.c
> @@ -954,11 +954,13 @@ static long evdev_do_ioctl(struct file *file, unsigned int cmd,
>  			return -EFAULT;
>  
>  		error = input_ff_upload(dev, &effect, file);
> +		if (error)
> +			return error;
>  
>  		if (put_user(effect.id, &(((struct ff_effect __user *)p)->id)))
>  			return -EFAULT;
>  
> -		return error;
> +		return 0;
>  	}
>  
>  	/* Multi-number variable-length handlers */
> -- 
> 1.8.3.1
> 

-- 
Dmitry
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