Date:   Mon, 18 Mar 2019 15:44:55 +0100 (CET)
From:   Jiri Kosina <jikos@kernel.org>
To:     Andrej Shadura <andrew.shadura@collabora.co.uk>
cc:     linux-input@vger.kernel.org, linux-usb@vger.kernel.org,
        kernel@collabora.com, Theodore Ts'o <tytso@mit.edu>,
        Vasily Khoruzhick <anarsoul@gmail.com>,
        Nick Kossifidis <mickflemm@gmail.com>,
        linux-crypto@vger.kernel.org
Subject: Re: [PATCH v2] HID: add driver for U2F Zero built-in LED and RNG
In-Reply-To: <20190309183213.7598-1-andrew.shadura@collabora.co.uk>
Message-ID: <nycvar.YFH.7.76.1903181542260.19912@cbobk.fhfr.pm>
References: <20190309183213.7598-1-andrew.shadura@collabora.co.uk>
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On Sat, 9 Mar 2019, Andrej Shadura wrote:

> U2F Zero supports custom commands for blinking the LED and getting data
> from the internal hardware RNG. Expose the blinking function as a LED
> device, and the internal hardware RNG as an HWRNG so that it can be used
> to feed the enthropy pool.
> 
> Signed-off-by: Andrej Shadura <andrew.shadura@collabora.co.uk>
> ---
> 
> This version of the patch sets the quality to 1.
> 
> ---
>  drivers/hid/Kconfig       |  15 ++
>  drivers/hid/Makefile      |   1 +
>  drivers/hid/hid-ids.h     |   1 +
>  drivers/hid/hid-u2fzero.c | 371 ++++++++++++++++++++++++++++++++++++++
>  4 files changed, 388 insertions(+)
>  create mode 100644 drivers/hid/hid-u2fzero.c
> 
> diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
> index 41e9935fc584..4f1b8939561d 100644
> --- a/drivers/hid/Kconfig
> +++ b/drivers/hid/Kconfig
> @@ -989,6 +989,21 @@ config HID_UDRAW_PS3
>  	  Say Y here if you want to use the THQ uDraw gaming tablet for
>  	  the PS3.
>  
> +config HID_U2FZERO
> +	tristate "U2F Zero LED and RNG support"
> +	depends on HID
> +	depends on LEDS_CLASS
> +	help
> +	  Support for the LED of the U2F Zero device.
> +
> +	  U2F Zero supports custom commands for blinking the LED
> +	  and getting data from the internal hardware RNG.
> +	  The internal hardware can be used to feed the enthropy pool.
> +
> +	  U2F Zero only supports blinking its LED, so this driver doesn't
> +	  allow setting the brightness to anything but 1, which will
> +	  trigger a single blink and immediately reset to back 0.
> +

This driver isn't really a generic (transport-agnostic) one (which also 
means it's missing USB dependency in Kconfig btw).

Is there a reason why it can't be abstracted that way so that it'd fit our 
principal model in HID subsystem?

Also, I've looked at it really briefly, but can't it be easily implemented 
in userspace?

Thanks,

-- 
Jiri Kosina
SUSE Labs