linux-kernel - RE: [PATCH] devres: provide API devm

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Message-ID: <DU0PR04MB9417B76952E9B21E89946C09886D9@DU0PR04MB9417.eurprd04.prod.outlook.com>
Date:   Thu, 4 May 2023 08:59:41 +0000
From:   Peng Fan <peng.fan@....com>
To:     Greg KH <gregkh@...uxfoundation.org>,
        "Peng Fan (OSS)" <peng.fan@....nxp.com>
CC:     "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "rafael@...nel.org" <rafael@...nel.org>,
        "andriy.shevchenko@...ux.intel.com" 
        <andriy.shevchenko@...ux.intel.com>,
        "hdegoede@...hat.com" <hdegoede@...hat.com>,
        "jgg@...pe.ca" <jgg@...pe.ca>,
        "saravanak@...gle.com" <saravanak@...gle.com>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "abel.vesa@...aro.org" <abel.vesa@...aro.org>
Subject: RE: [PATCH] devres: provide API devm_kstrndup

Hi Greg,

> -----Original Message-----
> From: Greg KH <gregkh@...uxfoundation.org>
> Sent: 2023年5月4日 16:58
> To: Peng Fan (OSS) <peng.fan@....nxp.com>
> Cc: robh+dt@...nel.org; krzysztof.kozlowski+dt@...aro.org;
> rafael@...nel.org; andriy.shevchenko@...ux.intel.com;
> hdegoede@...hat.com; jgg@...pe.ca; saravanak@...gle.com;
> keescook@...omium.org; tglx@...utronix.de; linux-kernel@...r.kernel.org;
> abel.vesa@...aro.org; Peng Fan <peng.fan@....com>
> Subject: Re: [PATCH] devres: provide API devm_kstrndup
> 
> On Thu, May 04, 2023 at 03:57:54PM +0800, Peng Fan (OSS) wrote:
> > From: Peng Fan <peng.fan@....com>
> >
> > This patch introduces devm_kstrndup API so that the device's driver
> > can allocate memory and copy string.
> >
> > Signed-off-by: Peng Fan <peng.fan@....com>
> > ---
> >  drivers/base/devres.c  | 28 ++++++++++++++++++++++++++++
> > include/linux/device.h |  1 +
> >  2 files changed, 29 insertions(+)
> 
> We can not add apis with no users, please submit this at the same time a
> driver needs it.
> 
> And what driver would need to copy a string?

https://lore.kernel.org/all/20230504085506.504474-1-peng.fan@oss.nxp.com/

Should I submit V2 with the upper patch in a patchset?

Thanks,
Peng.

> 
> 
> >
> > diff --git a/drivers/base/devres.c b/drivers/base/devres.c index
> > 5c998cfac335..87e2965e5bab 100644
> > --- a/drivers/base/devres.c
> > +++ b/drivers/base/devres.c
> > @@ -963,6 +963,34 @@ char *devm_kstrdup(struct device *dev, const
> char
> > *s, gfp_t gfp)  }  EXPORT_SYMBOL_GPL(devm_kstrdup);
> >
> > +/**
> > + * devm_kstrndup - Allocate resource managed space and
> > + *                copy an existing string into that.
> > + * @dev: Device to allocate memory for
> > + * @s: the string to duplicate
> > + * @max: max length to duplicate
> > + * @gfp: the GFP mask used in the devm_kmalloc() call when allocating
> > +memory
> > + * RETURNS:
> > + * Pointer to allocated string on success, NULL on failure.
> > + */
> > +char *devm_kstrndup(struct device *dev, const char *s, size_t max,
> > +gfp_t gfp) {
> > +	size_t len;
> > +	char *buf;
> > +
> > +	if (!s)
> > +		return NULL;
> > +
> > +	len = strnlen(s, max);
> > +	buf = devm_kmalloc(dev, len + 1, gfp);
> > +	if (buf) {
> > +		memcpy(buf, s, len);
> > +		buf[len] = '\0';
> 
> Why not use kstrndup() instead of copying the same logic here?
> 
> thanks,
> 
> greg k-h