linux-kernel - Re: [PATCH] media: davinci/vpfe_capture.c: Avoid BUG

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Date:   Sun, 08 Dec 2019 06:44:11 -0300
From:   Ezequiel Garcia <ezequiel@...labora.com>
To:     Aditya Pakki <pakki001@....edu>
Cc:     kjlu@....edu, "Lad, Prabhakar" <prabhakar.csengg@...il.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media: davinci/vpfe_capture.c: Avoid BUG_ON for
 register failure

Hello Aditya,

On Fri, 2019-12-06 at 06:20 -0300, Ezequiel Garcia wrote:
> Hello Aditya,
> 
> Thanks for the patch.
> 
> On Thu, 2019-12-05 at 19:00 -0600, Aditya Pakki wrote:
> > In vpfe_register_ccdc_device(), failure to allocate dev->hw_ops
> > invokes calls to BUG_ON(). This patch returns the error to callers
> > instead of crashing.
> > 
> 
> I'm curious, are you actually getting this type of crash?
> 

Oops, it seems I was too fast to say this looked good.

The driver is not dynamically allocating dev->hw_ops;
as you can see hw_ops is not a pointer.

struct ccdc_hw_device {
        /* ccdc device name */
        char name[32];
        /* module owner */
        struct module *owner;
        /* hw ops */
        struct ccdc_hw_ops hw_ops;
};

Please, don't submit patches without testing, at the very
least compile testing.

Thanks,
Ezequiel

> > Signed-off-by: Aditya Pakki <pakki001@....edu>
> > ---
> >  drivers/media/platform/davinci/vpfe_capture.c | 21 ++++++-------------
> >  1 file changed, 6 insertions(+), 15 deletions(-)
> > 
> > diff --git a/drivers/media/platform/davinci/vpfe_capture.c b/drivers/media/platform/davinci/vpfe_capture.c
> > index 916ed743d716..6d394a006977 100644
> > --- a/drivers/media/platform/davinci/vpfe_capture.c
> > +++ b/drivers/media/platform/davinci/vpfe_capture.c
> > @@ -168,21 +168,11 @@ int vpfe_register_ccdc_device(const struct ccdc_hw_device *dev)
> >  	int ret = 0;
> >  	printk(KERN_NOTICE "vpfe_register_ccdc_device: %s\n", dev->name);
> >  
> > -	BUG_ON(!dev->hw_ops.open);
> > -	BUG_ON(!dev->hw_ops.enable);
> > -	BUG_ON(!dev->hw_ops.set_hw_if_params);
> > -	BUG_ON(!dev->hw_ops.configure);
> > -	BUG_ON(!dev->hw_ops.set_buftype);
> > -	BUG_ON(!dev->hw_ops.get_buftype);
> > -	BUG_ON(!dev->hw_ops.enum_pix);
> > -	BUG_ON(!dev->hw_ops.set_frame_format);
> > -	BUG_ON(!dev->hw_ops.get_frame_format);
> > -	BUG_ON(!dev->hw_ops.get_pixel_format);
> > -	BUG_ON(!dev->hw_ops.set_pixel_format);
> > -	BUG_ON(!dev->hw_ops.set_image_window);
> > -	BUG_ON(!dev->hw_ops.get_image_window);
> > -	BUG_ON(!dev->hw_ops.get_line_length);
> > -	BUG_ON(!dev->hw_ops.getfid);
> > +	if (!dev->hw_ops) {
> > +		printk(KERN_ERR "could not allocate hw_ops\n");
> 
> I'd drop this error message, as hw_ops is not really allocated here.
> 
> > +		ret = -EINVAL;
> > +		goto rvalue;
> 
> Instead of a goto to a return, just return -EINVAL here.
> 
> > +	}
> >  
> >  	mutex_lock(&ccdc_lock);
> >  	if (!ccdc_cfg) {
> > @@ -211,6 +201,7 @@ int vpfe_register_ccdc_device(const struct ccdc_hw_device *dev)
> >  	ccdc_dev = dev;
> >  unlock:
> >  	mutex_unlock(&ccdc_lock);
> > +rvalue:
> >  	return ret;
> >  }
> >  EXPORT_SYMBOL(vpfe_register_ccdc_device);
> 
> With those changes, the patch looks good.
> 
> Reviewed-by: Ezequiel Garcia <ezequiel@...labora.com>
> 
> Thanks,
> Ezequiel
>