netdev - Re: [PATCH v13 0/4] userspace MHI client interface driver

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Date:   Tue, 1 Dec 2020 12:40:50 -0700
From:   Jeffrey Hugo <jhugo@...eaurora.org>
To:     Jakub Kicinski <kuba@...nel.org>,
        Hemant Kumar <hemantk@...eaurora.org>
Cc:     manivannan.sadhasivam@...aro.org, gregkh@...uxfoundation.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        bbhatt@...eaurora.org, loic.poulain@...aro.org,
        netdev@...r.kernel.org, linux-wireless@...r.kernel.org,
        Kalle Valo <kvalo@...eaurora.org>
Subject: Re: [PATCH v13 0/4] userspace MHI client interface driver

On 12/1/2020 12:29 PM, Jakub Kicinski wrote:
> On Fri, 27 Nov 2020 19:26:02 -0800 Hemant Kumar wrote:
>> This patch series adds support for UCI driver. UCI driver enables userspace
>> clients to communicate to external MHI devices like modem and WLAN. UCI driver
>> probe creates standard character device file nodes for userspace clients to
>> perform open, read, write, poll and release file operations. These file
>> operations call MHI core layer APIs to perform data transfer using MHI bus
>> to communicate with MHI device. Patch is tested using arm64 based platform.
> 
> Wait, I thought this was for modems.
> 
> Why do WLAN devices need to communicate with user space?
> 

Why does it matter what type of device it is?  Are modems somehow unique 
in that they are the only type of device that userspace is allowed to 
interact with?

However, I'll bite.  Once such usecase would be QMI.  QMI is a generic 
messaging protocol, and is not strictly limited to the unique operations 
of a modem.

Another usecase would be Sahara - a custom file transfer protocol used 
for uploading firmware images, and downloading crashdumps.

Off the top of my head, this driver is useful for modems, wlan, and AI 
accelerators.

-- 
Jeffrey Hugo
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.