linux-kernel - Re: [PATCH] mfd: cros_ec_dev: Add a poll handler to receive MKBP events

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Message-ID: <20190402040647.GM4187@dell>
Date:   Tue, 2 Apr 2019 05:06:47 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Enric Balletbo i Serra <enric.balletbo@...labora.com>
Cc:     gwendal@...omium.org, bleung@...omium.org,
        linux-kernel@...r.kernel.org, groeck@...omium.org,
        kernel@...labora.com, dtor@...omium.org,
        Vincent Palatin <vpalatin@...omium.org>
Subject: Re: [PATCH] mfd: cros_ec_dev: Add a poll handler to receive MKBP
 events

On Fri, 08 Mar 2019, Enric Balletbo i Serra wrote:

> From: Vincent Palatin <vpalatin@...omium.org>
> 
> Allow to poll on the cros_ec device to receive the MKBP events.
> 
> The /dev/cros_[ec|fp|..] file operations now implements the poll
> operation. The userspace can now receive specific MKBP events by doing the
> following:
> - Open the /dev/cros_XX file.
> - Call the CROS_EC_DEV_IOCEVENTMASK ioctl with the bitmap of the MKBP
>   events it wishes to receive as argument.
> - Poll on the file descriptor.
> - When it gets POLLIN, do a read on the file descriptor, the first
>   queued event will be returned (using the struct
>   ec_response_get_next_event format: one byte of event type, then
>   the payload).
> 
> The read() operation returns at most one event even if there are several
> queued, and it might be truncated if the buffer is smaller than the
> event (but the caller should know the maximum size of the events it is
> reading).
> 
> read() used to return the EC version string, it still does it when no
> event mask or an empty event is set for backward compatibility (despite
> nobody really using this feature).
> 
> This will be used, for example, by the userspace daemon to receive and
> treat the EC_MKBP_EVENT_FINGERPRINT sent by the FP MCU.

MFD does not seem like the correct place for this.  Maybe this is a
good candidate for drivers/platform/chrome/* where the rest of your
platform empire now resides.

> Signed-off-by: Vincent Palatin <vpalatin@...omium.org>
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>
> ---
> 
>  drivers/mfd/cros_ec_dev.c | 163 +++++++++++++++++++++++++++++++++++++-
>  drivers/mfd/cros_ec_dev.h |   1 +
>  2 files changed, 160 insertions(+), 4 deletions(-)

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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