linux-kernel - Re: [PATCH] staging: pi433: enforce tx_cfg to be set before any message can be sent

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Message-ID: <20220112084002.GA27596@mail.google.com>
Date:   Wed, 12 Jan 2022 21:40:02 +1300
From:   Paulo Miguel Almeida <paulo.miguel.almeida.rodenas@...il.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     gregkh@...uxfoundation.org, realwakka@...il.com,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: pi433: enforce tx_cfg to be set before any
 message can be sent

On Mon, Jan 10, 2022 at 12:17:23PM +0300, Dan Carpenter wrote:
> Seems reasonable.
> 
> On Sun, Jan 09, 2022 at 11:26:52AM +1300, Paulo Miguel Almeida wrote:
> > meta-comments:
> > - I'm not entirely sure if -EPERM is the best error code to return here,
> >   I'm taking suggestions
> 
> Better to just return -EINVAL.

> > ---
> >  drivers/staging/pi433/pi433_if.c | 16 +++++++++++++++-
> >  1 file changed, 15 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/staging/pi433/pi433_if.c b/drivers/staging/pi433/pi433_if.c
> > index 051c9052aeeb..3e9913f4bc7d 100644
> > --- a/drivers/staging/pi433/pi433_if.c
> > +++ b/drivers/staging/pi433/pi433_if.c
> > @@ -108,6 +108,9 @@ struct pi433_device {
> >  struct pi433_instance {
> >  	struct pi433_device	*device;
> >  	struct pi433_tx_cfg	tx_cfg;
> > +
> > +	/* control flags */
> > +	bool			tx_cfg_initialized;
> >  };
> >  
> >  /*-------------------------------------------------------------------------*/
> > @@ -823,6 +826,16 @@ pi433_write(struct file *filp, const char __user *buf,
> >  	if (count > MAX_MSG_SIZE)
> >  		return -EMSGSIZE;
> >  
> > +	/*
> > +	 * check if tx_cfg has been initialized otherwise we won't be able to
> > +	 * config the RF trasmitter correctly due to invalid settings
> > +	 */
> > +	if (!instance->tx_cfg_initialized) {
> > +		dev_dbg(device->dev,
> > +			"write: failed due to uninitialized tx_cfg");
> 
> Use dev_notice_once() or similar.  Maybe "unconfigured" instead of
> uninitialized?
> 
> 	dev_notice_once(device->dev,
> 			"write: failed due to unconfigured tx_cfg (see PI433_IOC_WR_TX_CFG)");
> 
> 
> > +		return -EPERM;
> > +	}
> > +
> >  	/*
> >  	 * write the following sequence into fifo:
> >  	 * - tx_cfg
> > @@ -897,6 +910,7 @@ pi433_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
> >  			return -EFAULT;
> >  		mutex_lock(&device->tx_fifo_lock);
> >  		memcpy(&instance->tx_cfg, &tx_cfg, sizeof(struct pi433_tx_cfg));
> > +		instance->tx_cfg_initialized = true;
> >  		mutex_unlock(&device->tx_fifo_lock);
> >  		break;
> >  	case PI433_IOC_RD_RX_CFG:
> > @@ -950,7 +964,7 @@ static int pi433_open(struct inode *inode, struct file *filp)
> >  	/* setup instance data*/
> >  	instance->device = device;
> >  	instance->tx_cfg.bit_rate = 4711;
> 
> This is sort of pointless because it can't work until that gets over
> written.
> 
> 
> > -	// TODO: fill instance->tx_cfg;
> > +	instance->tx_cfg_initialized = false;
> 
> kzalloc() will already set this to false.
> 
> regards,
> dan carpenter
> 

I agree with you on all points mentioned above. I will send another
version of this patch shortly.

Thanks for the patch review.

Paulo A.