linux-kernel - Re: [PATCH 1/2] soc: qcom: smsm: Handle probe deferral

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Date:   Tue, 4 Apr 2017 04:38:07 +0200
From:   Jonathan Neuschäfer <j.neuschaefer@....net>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Jonathan Neusch?fer <j.neuschaefer@....net>,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] soc: qcom: smsm: Handle probe deferral

On Mon, Mar 27, 2017 at 11:18:29PM -0700, Bjorn Andersson wrote:
> On Wed 15 Mar 04:43 PDT 2017, Jonathan Neusch?fer wrote:
[...]
> >  	info = qcom_smem_get(QCOM_SMEM_HOST_ANY, SMEM_SMSM_SIZE_INFO, &size);
> > -	if (PTR_ERR(info) == -ENOENT || size != sizeof(*info)) {
> > +	if (PTR_ERR(info) == -EPROBE_DEFER) {
> > +		return PTR_ERR(info);
> > +	} else if (PTR_ERR(info) == -ENOENT || size != sizeof(*info)) {
> 
> The following elseif was supposed to take care of this case, but I
> clearly screwed this up.
> 
> Rather than adding a special case for EPROBE_DEFER before the two checks
> and then fix up the original expression to make errors fall back to the
> original else, I think you should rearrange the conditionals.
> 
> Probably better to write it like this instead:
> 
>         if (IS_ERR(info) && PTR_ERR(info) != -ENOENT) {
>                 if (PTR_ERR(info) != -EPROBE_DEFER)
>                         dev_err(smsm->dev, "unable to retrieve smsm size info\n");
>                 return PTR_ERR(info);
>         } else if (IS_ERR(info) || size != sizeof(*info)) {
>                 dev_warn(smsm->dev, "no smsm size info, using defaults\n");
>                 smsm->num_entries = SMSM_DEFAULT_NUM_ENTRIES;
>                 smsm->num_hosts = SMSM_DEFAULT_NUM_HOSTS;
>                 return 0;
>         }

Indeed, this looks better.

And it also obsoletes my patch 2/2, which is nice.

> >  		dev_warn(smsm->dev, "no smsm size info, using defaults\n");
> >  		smsm->num_entries = SMSM_DEFAULT_NUM_ENTRIES;
> >  		smsm->num_hosts = SMSM_DEFAULT_NUM_HOSTS;
> > @@ -515,7 +517,9 @@ static int qcom_smsm_probe(struct platform_device *pdev)
> >  	/* Acquire the main SMSM state vector */
> >  	ret = qcom_smem_alloc(QCOM_SMEM_HOST_ANY, SMEM_SMSM_SHARED_STATE,
> >  			      smsm->num_entries * sizeof(u32));
> > -	if (ret < 0 && ret != -EEXIST) {
> > +	if (ret == -EPROBE_DEFER) {
> > +		return ret;
> > +	} else if (ret < 0 && ret != -EEXIST) {
> 
> The idiomatic way to write this is:
> 
> if (ret < 0 && ret != -EEXIST) {
> 	if (ret != -EPROBE_DEFER)
> 		dev_err();
> 	return ret;
> }
> 
> However, for us to reach this point in smsm_probe() the above
> qcom_smem_get() must have returned successfully, i.e. we have SMEM in
> place so there's no need to handle this case specifically.

I came to the same conclusion but wasn't sure. I'll drop this part from
my patch.

I'll send a v2 of this series, although after applying your suggestions,
I can't claim much originality anymore.


Thanks for the review,
Jonathan Neuschäfer

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