linux-kernel - Re: [PATCH v3] i2c: i2c-qcom-geni: Parse Error correctly in i2c GSI mode

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Date: Fri, 8 Mar 2024 08:02:10 +0100
From: Andi Shyti <andi.shyti@...nel.org>
To: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
Cc: konrad.dybcio@...aro.org, andersson@...nel.org, vkoul@...nel.org, 
	wsa@...nel.org, linux-arm-msm@...r.kernel.org, dmaengine@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org, quic_vdadhani@...cinc.com
Subject: Re: [PATCH v3] i2c: i2c-qcom-geni: Parse Error correctly in i2c GSI
 mode

Hi Mukesh,

..

> > > Fixes: d8703554f4de ("i2c: qcom-geni: Add support for GPI DMA")
> > 
> > I still don't understand what's the fix here. You are making a
> > generic DMA error to be more specific... where is the bug? What
> > exactly is broken now?
> > 
> This is about being particular while reporting specific error.
> Like i mentioned, instead of generic DMA transfer error, it should be
> particular error 1) NACK 2) BUT_PROTO 3)ARB_LOST.
> Ofcourse when data transfer via DMA fails, it can be considered as
> DMA Txfer fail.
> In summary so far driver was considering all failure as txfer failure,
> but i2c has errors which are kind of response/condition on the bus.

I understand that, but what I need to know is: does the system
crash? does the system act in unexpected way?

Moving from "you received an error" to "you received a nack" is
not a fix, it's an improvement and it should not have the Fixes
tag.

Having the Fixes tag decides which path this patch will take to
to reach upstream. It's important because after it gets to
upstream other people will take your patch and backport it older
kernels.

I want to avoid this extra work when not necessary.

> Sorry if it confusing still, but please let me know if anything required to
> be updated in  commit log which can bring clarity.
> 
> > Besides, keep in mind, that commits with fixes tags get
> > backported to older kernels (this one dates back to 5.18) and you
> > should also Cc the stable mailing list:
> > 
> > Cc: <stable@...r.kernel.org> # v5.18+
> 
> Sure, will add into CC. was waiting for reviewed-by tag.

No need to resend.

Thanks,
Andi