linux-kernel - Re: [PATCH 0/6] In-kernel QMI handling

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Date:   Fri, 04 Aug 2017 10:36:07 -0500
From:   Dan Williams <dcbw@...hat.com>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        "David S. Miller" <davem@...emloft.net>,
        Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>
Cc:     linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/6] In-kernel QMI handling

On Fri, 2017-08-04 at 07:59 -0700, Bjorn Andersson wrote:
> This series starts by moving the common definitions of the QMUX
> protocol to the
> uapi header, as they are shared with clients - both in kernel and
> userspace.
> 
> This series then introduces in-kernel helper functions for aiding the
> handling
> of QMI encoded messages in the kernel. QMI encoding is a wire-format
> used in
> exchanging messages between the majority of QRTR clients and
> services.

This raises a few red-flags for me.  So far, we've kept almost
everything QMI related in userspace and handled all QMI control-channel 
messages from libraries like libqmi or uqmi via the cdc-wdm driver and
the "rmnet" interface via the qmi_wwan driver.  The kernel drivers just
serve as the transport.

Can you describe what kinds of in-kernel drivers need to actually parse
QMI messages as part of their operation?

Dan

> It then adds an abstractions to reduce the duplication of common code
> in
> drivers that needs to query the name server and send and receive
> encoded
> messages to a remote service.
> 
> Finally it introduces a sample implementation for showing QRTR and
> the QMI
> helpers in action. The sample device instantiates in response to
> finding the
> "test service" and implements the "test protocol".
> 
> Bjorn Andersson (6):
>   net: qrtr: Invoke sk_error_report() after setting sk_err
>   net: qrtr: Move constants to header file
>   net: qrtr: Add control packet definition to uapi
>   soc: qcom: Introduce QMI encoder/decoder
>   soc: qcom: Introduce QMI helpers
>   samples: Introduce Qualcomm QRTR sample client
> 
>  drivers/soc/qcom/Kconfig          |   8 +
>  drivers/soc/qcom/Makefile         |   3 +
>  drivers/soc/qcom/qmi_encdec.c     | 812
> ++++++++++++++++++++++++++++++++++++++
>  drivers/soc/qcom/qmi_interface.c  | 540 +++++++++++++++++++++++++
>  include/linux/soc/qcom/qmi.h      | 249 ++++++++++++
>  include/uapi/linux/qrtr.h         |  35 ++
>  net/qrtr/qrtr.c                   |  16 +-
>  samples/Kconfig                   |   8 +
>  samples/Makefile                  |   2 +-
>  samples/qrtr/Makefile             |   1 +
>  samples/qrtr/qrtr_sample_client.c | 603 ++++++++++++++++++++++++++++
>  11 files changed, 2261 insertions(+), 16 deletions(-)
>  create mode 100644 drivers/soc/qcom/qmi_encdec.c
>  create mode 100644 drivers/soc/qcom/qmi_interface.c
>  create mode 100644 include/linux/soc/qcom/qmi.h
>  create mode 100644 samples/qrtr/Makefile
>  create mode 100644 samples/qrtr/qrtr_sample_client.c
>