linux-kernel - Re: [PATCH] coresight: Use devm_bitmap

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Date:   Thu, 28 Oct 2021 10:44:37 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc:     Joe Perches <joe@...ches.com>, suzuki.poulose@....com,
        mike.leach@...aro.org, leo.yan@...aro.org,
        alexander.shishkin@...ux.intel.com, mcoquelin.stm32@...il.com,
        alexandre.torgue@...s.st.com, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] coresight: Use devm_bitmap_zalloc when applicable

Good day,

On Sat, Oct 23, 2021 at 10:09:14PM +0200, Christophe JAILLET wrote:
> Le 23/10/2021 à 21:36, Joe Perches a écrit :
> > On Sat, 2021-10-23 at 21:24 +0200, Christophe JAILLET wrote:
> > > 'drvdata->chs.guaranteed' is a bitmap. So use 'devm_bitmap_kzalloc()' to
> > > simplify code, improve the semantic and avoid some open-coded arithmetic
> > > in allocator arguments.
> > []
> > > diff --git a/drivers/hwtracing/coresight/coresight-stm.c b/drivers/hwtracing/coresight/coresight-stm.c
> > []
> > > @@ -862,7 +862,6 @@ static int stm_probe(struct amba_device *adev, const struct amba_id *id)
> > >   	struct stm_drvdata *drvdata;
> > >   	struct resource *res = &adev->res;
> > >   	struct resource ch_res;
> > > -	size_t bitmap_size;
> > >   	struct coresight_desc desc = { 0 };
> > >   	desc.name = coresight_alloc_device_name(&stm_devs, dev);
> > > @@ -904,9 +903,7 @@ static int stm_probe(struct amba_device *adev, const struct amba_id *id)
> > >   	else
> > >   		drvdata->numsp = stm_num_stimulus_port(drvdata);
> > > -	bitmap_size = BITS_TO_LONGS(drvdata->numsp) * sizeof(long);
> > > -
> > > -	guaranteed = devm_kzalloc(dev, bitmap_size, GFP_KERNEL);
> > > +	guaranteed = devm_bitmap_zalloc(dev, drvdata->numsp, GFP_KERNEL);
> > >   	if (!guaranteed)
> > >   		return -ENOMEM;
> > >   	drvdata->chs.guaranteed = guaranteed;
> > 
> > guaranteed is also pretty useless
> > 
> 
> I agree, but removing it would make the line with devm_bitmap_zalloc() 86
> chars. This would not be consistent with the rest of the file and would
> (IMHO) require splitting.
> 
> Let see if the maintainer prefer saving one additional line of code, or
> keeping the logic in place.

I think we can get rid of @guaranteed and splitting is fine with me:

        drvdata->chs.guaranteed = devm_bitmap_zalloc(dev,
                                                     drvdata->numsp,
                                                     GFP_KERNEL);

Thanks,
Mathieu


> 
> CJ
>