linux-kernel - Re: [PATCH] usb: gadget: udc: atmel: used managed kasprintf

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Date:   Mon, 16 Jan 2017 12:11:28 +0100
From:   Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:     Felipe Balbi <balbi@...nel.org>
Cc:     David Laight <David.Laight@...LAB.COM>,
        Nicolas Ferre <nicolas.ferre@...el.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Subject: Re: [PATCH] usb: gadget: udc: atmel: used managed kasprintf

On 16/01/2017 at 12:27:04 +0200, Felipe Balbi wrote :
> 
> Hi,
> 
> David Laight <David.Laight@...LAB.COM> writes:
> > From: Alexandre Belloni
> >> Sent: 02 December 2016 16:19
> >> On 02/12/2016 at 15:59:57 +0000, David Laight wrote :
> >> > From: Alexandre Belloni
> >> > > Sent: 01 December 2016 10:27
> >> > > Use devm_kasprintf instead of simple kasprintf to free the allocated memory
> >> > > when needed.
> >> >
> >> > s/when needed/when the device is freed/
> >> >
> >> > > Suggested-by: Peter Rosin <peda@...ntia.se>
> >> > > Signed-off-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
> >> > > ---
> >> > >  drivers/usb/gadget/udc/atmel_usba_udc.c | 3 ++-
> >> > >  1 file changed, 2 insertions(+), 1 deletion(-)
> >> > >
> >> > > diff --git a/drivers/usb/gadget/udc/atmel_usba_udc.c b/drivers/usb/gadget/udc/atmel_usba_udc.c
> >> > > index 45bc997d0711..aec72fe8273c 100644
> >> > > --- a/drivers/usb/gadget/udc/atmel_usba_udc.c
> >> > > +++ b/drivers/usb/gadget/udc/atmel_usba_udc.c
> >> > > @@ -1978,7 +1978,8 @@ static struct usba_ep * atmel_udc_of_init(struct platform_device *pdev,
> >> > >  			dev_err(&pdev->dev, "of_probe: name error(%d)\n", ret);
> >> > >  			goto err;
> >> > >  		}
> >> > > -		ep->ep.name = kasprintf(GFP_KERNEL, "ep%d", ep->index);
> >> > > +		ep->ep.name = devm_kasprintf(&pdev->dev, GFP_KERNEL, "ep%d",
> >> > > +					     ep->index);
> >> >
> >> > Acually why bother mallocing such a small string at all.
> >> > The maximum length is 12 bytes even if 'index' are unrestricted.
> >> >
> >> 
> >> IIRC, using statically allocated string is failing somewhere is the USB
> >> core but I don't remember all the details.
> >
> > I can't imagine that changing ep->ep.name from 'char *' to 'char [12]' would
> > make any difference.
> 
> the actual name is managed by the UDC. Meaning, ep->ep.name should be a
> pointer, but it could very well just point to ep->name which would be
> char [12].
> 

Yeah, I sent a patch that did just that.
http://lists.infradead.org/pipermail/linux-arm-kernel/2017-January/478602.html

-- 
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com