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From: Johan Hovold <johan@kernel.org>
To: Sean Young <sean@mess.org>
Cc: linux-media@vger.kernel.org, linux-usb@vger.kernel.org,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Jon Rhees <support@usbuirt.com>, Oliver Neukum <oneukum@suse.com>
Subject: Re: [PATCH v3 0/3] IR driver for USB-UIRT device
Date: Thu, 20 May 2021 15:40:22 +0200	[thread overview]
Message-ID: <YKZmxkmRXYRnTL/o@hovoldconsulting.com> (raw)
In-Reply-To: <20210517123509.GA6597@gofer.mess.org>

On Mon, May 17, 2021 at 01:35:09PM +0100, Sean Young wrote:
> On Mon, May 17, 2021 at 11:35:22AM +0100, Sean Young wrote:
> > On Mon, May 17, 2021 at 11:30:39AM +0200, Johan Hovold wrote:

> > > Ok, but apart from BPF that sound like other stuff and not the three
> > > items you list above? Is there anything preventing those items from
> > > being implemented in user space?
> > 
> > Well, after IR is decoded, you want to send decoded scancodes/key codes
> > to any input device, so your remote works just like any input device.
> 
> There is another advantage. IR decoding in userspace involves a lot more
> context switches/scheduling, and it can feel laggy when the cpu is under
> load (e.g. video decoding on the CPU). When you press pause/play/stop or
> so you expect the response the instantatiously. A 100ms delay is noticable.

RT scheduling? Sounds like you should be able to handle this way faster
than 100 ms.

> Alternatively the key-up events get delayed and you end up with multiple
> un-intended button repeats. None of this happens with kernel decoding and
> it feels very snappy.

Yeah, perhaps it's best handled in-kernel, but it seems we should be
able to handle a simple key press within 20 ms or whatever the critical
latency is here using either option (kernel or user-space driver).

Johan

  reply	other threads:[~2021-05-20 13:40 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-06 12:44 [PATCH v3 0/3] IR driver for USB-UIRT device Sean Young
2021-05-06 12:44 ` [PATCH v3 1/3] USB: serial: move ftdi_sio.h into include directories Sean Young
2021-05-14 11:16   ` Johan Hovold
2021-05-06 12:44 ` [PATCH v3 2/3] media: rc: new driver for USB-UIRT device Sean Young
2021-05-14 11:38   ` Johan Hovold
2021-05-15  9:52     ` Sean Young
2021-05-17  9:38       ` Johan Hovold
2021-05-06 12:44 ` [PATCH v3 3/3] USB: serial: blacklist USB-UIRT when driver is selected Sean Young
2021-05-14 11:40   ` Johan Hovold
2021-05-15  9:56     ` Sean Young
2021-05-17  9:40       ` Johan Hovold
2021-05-10  8:15 ` [PATCH v3 0/3] IR driver for USB-UIRT device Johan Hovold
2021-05-11 10:32   ` Sean Young
2021-05-14 11:16     ` Johan Hovold
2021-05-15  9:22       ` Sean Young
2021-05-17  9:30         ` Johan Hovold
2021-05-17 10:35           ` Sean Young
2021-05-17 12:35             ` Sean Young
2021-05-20 13:40               ` Johan Hovold [this message]
2021-05-20 13:31             ` Johan Hovold
2021-05-21 11:39               ` Sean Young
2021-06-23 12:48                 ` Johan Hovold
2021-05-25 12:25               ` Oliver Neukum
2021-06-23 13:10                 ` Johan Hovold
2021-06-24  9:13                   ` Sean Young
2021-06-24  9:41                     ` Johan Hovold
2021-06-25  8:08                       ` Sean Young
2021-07-02 10:44                         ` Johan Hovold

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