From mboxrd@z Thu Jan  1 00:00:00 1970
From: kristof@sigsegv.be (Kristof Provost)
Date: Wed, 8 Oct 2014 17:57:50 +0200
Subject: User space <==> kernel space for device wakeups.
In-Reply-To: <CAC-LjFv7pDX0RRup7tywrRRJEf6_tCoVaTgqFCd0fVxZSMkbhA@mail.gmail.com>
References: <CAB6A5-ALq0WT2CKAOYX-O+-OgYJcr0G8OWz6EFkqb-Z6QGA2Bw@mail.gmail.com>
	<20141008132941.GB5119@kroah.com>
	<CAC-LjFv7pDX0RRup7tywrRRJEf6_tCoVaTgqFCd0fVxZSMkbhA@mail.gmail.com>
Message-ID: <20141008155750.GF2017@vega.codepro.be>
To: kernelnewbies@lists.kernelnewbies.org
List-Id: kernelnewbies.lists.kernelnewbies.org

On 2014-10-08 21:14:43 (+0530), Jeshwanth Kumar N K <jeshkumar555@gmail.com> wrote:
> Wayback when I was working on some project to wake up userspace program for
> every rising edge in GPIO pin (hall sensor), I use to send signal to the
> PID from kernel, before that userspace has to register its PID with kernel
> module. 
> 
I've seen a certain vendor[1] do something similar. They saved the task
pointer for whichever process made the magical ioctl() call and used it
to send signals from the interrupt handler. It worked, right up to the
point where the process went away and then the kernel panicked.

Regards,
Kristof

[1] Who shall remain nameless here. Naming them would only give people
    the impression that other vendors might be better.