linux-kernel - Re: [PATCH] hid-input: Use a larger event buffer for MT devices

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Message-ID: <AANLkTinI8w5vCi-VOf_IybZmOBDe8gjlJymZNSmmpkpk@mail.gmail.com>
Date:	Mon, 14 Jun 2010 09:17:49 -0700
From:	Ping Cheng <pinglinux@...il.com>
To:	Henrik Rydberg <rydberg@...omail.se>
Cc:	Jiri Kosina <jkosina@...e.cz>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	Stephane Chatty <chatty@...c.fr>,
	Rafi Rubin <rafi@...s.upenn.edu>,
	Michael Poole <mdpoole@...ilus.org>
Subject: Re: [PATCH] hid-input: Use a larger event buffer for MT devices

On Mon, Jun 14, 2010 at 4:49 AM, Henrik Rydberg <rydberg@...omail.se> wrote:
> The MT devices produce a lot of data. Tell the underlying input device
> approximately how many events will be sent per synchronization, to allow
> for better buffering. The number is a template based on continuously
> reporting details for each finger on a single hand.
>
> Signed-off-by: Henrik Rydberg <rydberg@...omail.se>
> ---
> Hi Jiri,
>
> This patch goes together with the evdev buffer patchset, which Dmitry
> is going to queue for 2.6.36.
>
> Cheers,
> Henrik
>
>  drivers/hid/hid-input.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
> index 7a0d2e4..69d152e 100644
> --- a/drivers/hid/hid-input.c
> +++ b/drivers/hid/hid-input.c
> @@ -534,6 +534,9 @@ mapped:
>                        input_set_abs_params(input, usage->code, a, b, (b - a) >> 8, (b - a) >> 4);
>                else    input_set_abs_params(input, usage->code, a, b, 0, 0);
>
> +               /* use a larger default input buffer for MT devices */
> +               if (usage->code == ABS_MT_POSITION_X && input->hint_events_per_packet == 0)
> +                       input_set_events_per_packet(input, 60);

Do we really want to use a hardcoded number here? Considering you have
used the same value in your "input: bcm5974" patch, adding it as an
ifdef in linux/input.h should not be an overkill in design and offers
the other drivers a chance to use it.

Ping

>        }
>
>        if (usage->type == EV_ABS &&
> --
> 1.6.3.3
>
> --
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