linux-kernel - Re: [patch] drm/amd: cleanup get_mfd_cell

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Date:	Sat, 27 Feb 2016 13:40:49 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	walter harms <wharms@....de>
Cc:	David Airlie <airlied@...ux.ie>,
	Alex Deucher <alexander.deucher@....com>,
	Maruthi Srinivas Bayyavarapu <Maruthi.Bayyavarapu@....com>,
	Jammy Zhou <Jammy.Zhou@....com>,
	Murali Krishna Vemuri <murali-krishna.vemuri@....com>,
	Chunming Zhou <david1.zhou@....com>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [patch] drm/amd: cleanup get_mfd_cell_dev()

On Sat, Feb 27, 2016 at 10:50:40AM +0100, walter harms wrote:
> 
> 
> Am 25.02.2016 08:47, schrieb Dan Carpenter:
> > It's simpler to just use snprintf() to print this to one buffer instead
> > of using strcpy() and strcat().  Also using snprintf() is slightly safer
> > than using sprintf().
> > 
> > Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> > 
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_acp.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_acp.c
> > index 9f8cfaa..d6b0bff 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_acp.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_acp.c
> > @@ -240,12 +240,10 @@ static int acp_poweron(struct generic_pm_domain *genpd)
> >  static struct device *get_mfd_cell_dev(const char *device_name, int r)
> >  {
> >  	char auto_dev_name[25];
> > -	char buf[8];
> >  	struct device *dev;
> >  
> > -	sprintf(buf, ".%d.auto", r);
> > -	strcpy(auto_dev_name, device_name);
> > -	strcat(auto_dev_name, buf);
> > +	snprintf(auto_dev_name, sizeof(auto_dev_name),
> > +		 "%s.%d.auto", device_name, r);
> >  	dev = bus_find_device_by_name(&platform_bus_type, NULL, auto_dev_name);
> >  	dev_info(dev, "device %s added to pm domain\n", auto_dev_name);
> >  
> 
> hi,
> i tried to understand what is the base for char auto_dev_name[25]. It is not clear
> from these snipped if that is large or small.
> 
> (To be aware i assume that
> get_mfd_cell_dev("terrible_long_and_Stupid_name",1234567899346712) will never happen
> but i could find no reason)
> 
> A small comment that explains the magic 25 would be nice.

I have no idea, either of course.  For example,
mc13xxx_add_subdevice_pdata() assumes device_name by itself can be 30
characters.  Hence the change to snprintf.

regards,
dan carpenter