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

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Message-ID: <20201202041559.GA3241@thinkpad>
Date:   Wed, 2 Dec 2020 09:45:59 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Jeffrey Hugo <jhugo@...eaurora.org>,
        Hemant Kumar <hemantk@...eaurora.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 Tue, Dec 01, 2020 at 12:03:02PM -0800, Jakub Kicinski wrote:
> On Tue, 1 Dec 2020 12:40:50 -0700 Jeffrey Hugo wrote:
> > 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?
> 
> Yes modems are traditionally highly weird and require some serial
> device dance I don't even know about.
> 
> We have proper interfaces in Linux for configuring WiFi which work
> across vendors. Having char device access to WiFi would be a step 
> back.
> 

This is not for configuring the WiFi. This driver is mostly used for modems and
the AI accelerator Jeff is working on. But there might be a usecase for WLAN
devices as well to collect crash dumps and download fw (typical vendor ways) but
having those features are add-ons IMO.

So I think we should not be blocked by those usecases.

Thanks,
Mani