linux-kernel - Re: [PATCH V2 2/3] soc: ti: knav_dma: Make knav_dma_open

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Message-ID: <20251001105721.wf6mr2ysj34uhkhh@rendition>
Date: Wed, 1 Oct 2025 05:57:21 -0500
From: Nishanth Menon <nm@...com>
To: Jacob Keller <jacob.e.keller@...el.com>
CC: Uwe Kleine-König <u.kleine-koenig@...libre.com>,
        Paolo
 Abeni <pabeni@...hat.com>, Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet
	<edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Andrew Lunn
	<andrew+netdev@...n.ch>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        Simon
 Horman <horms@...nel.org>,
        Siddharth Vadapalli <s-vadapalli@...com>,
        <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <netdev@...r.kernel.org>
Subject: Re: [PATCH V2 2/3] soc: ti: knav_dma: Make knav_dma_open_channel
 return NULL on error

On 16:59-20250930, Jacob Keller wrote:
> 
> 
> On 9/30/2025 5:16 AM, Nishanth Menon wrote:
> > Make knav_dma_open_channel consistently return NULL on error instead of
> > ERR_PTR. Currently the header include/linux/soc/ti/knav_dma.h returns NUL
> > when the driver is disabled, but the driver implementation returns
> > ERR_PTR(-EINVAL), creating API inconsistency for users.
> > 
> 
> I would word this as indicating that we don't even use ERR_PTR here at all!

Thanks. Yep, will do for the next respin.

> 
> > Standardize the error handling by making the function return NULL on all
> > error conditions.
> > 
> > Suggested-by: Simon Horman <horms@...nel.org>
> > Signed-off-by: Nishanth Menon <nm@...com>
> > ---
> > Changes in V2:
> > * renewed version
> > 
> >  drivers/soc/ti/knav_dma.c | 14 +++++++-------
> >  1 file changed, 7 insertions(+), 7 deletions(-)
> > 
> > diff --git a/drivers/soc/ti/knav_dma.c b/drivers/soc/ti/knav_dma.c
> > index a25ebe6cd503..e69f0946de29 100644
> > --- a/drivers/soc/ti/knav_dma.c
> > +++ b/drivers/soc/ti/knav_dma.c
> > @@ -402,7 +402,7 @@ static int of_channel_match_helper(struct device_node *np, const char *name,
> >   * @name:	slave channel name
> >   * @config:	dma configuration parameters
> >   *
> > - * Returns pointer to appropriate DMA channel on success or error.
> > + * Returns pointer to appropriate DMA channel on success or NULL on error.
> >   */
> >  void *knav_dma_open_channel(struct device *dev, const char *name,
> >  					struct knav_dma_cfg *config)
> > @@ -414,13 +414,13 @@ void *knav_dma_open_channel(struct device *dev, const char *name,
> >  
> >  	if (!kdev) {
> >  		pr_err("keystone-navigator-dma driver not registered\n");
> > -		return (void *)-EINVAL;
> > +		return NULL;
> 
> Wow. The driver doesn't even return ERR_PTR, but just directly casts
> -EINVAL to a void *... thats quite ugly. Good to remove this.
> 




-- 
Regards,
Nishanth Menon
Key (0xDDB5849D1736249D) / Fingerprint: F8A2 8693 54EB 8232 17A3  1A34 DDB5 849D 1736 249D
https://ti.com/opensource