RE: [PATCH v3 2/4] rtc: pcf85363: Add support for NXP pcf85263 rtc

From: Biju Das <biju.das@bp.renesas.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>,
	Alessandro Zummo <a.zummo@towertech.it>,
	Geert Uytterhoeven <geert+renesas@glider.be>,
	"linux-rtc@vger.kernel.org" <linux-rtc@vger.kernel.org>,
	Simon Horman <horms@verge.net.au>,
	Chris Paterson <Chris.Paterson2@renesas.com>,
	Fabrizio Castro <fabrizio.castro@bp.renesas.com>,
	Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
	Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Subject: RE: [PATCH v3 2/4] rtc: pcf85363: Add support for NXP pcf85263 rtc
Date: Fri, 7 Dec 2018 10:16:41 +0000	[thread overview]
Message-ID: <OSBPR01MB21030916075015094519D0F2B8AA0@OSBPR01MB2103.jpnprd01.prod.outlook.com> (raw)
In-Reply-To: <CAMuHMdUXPPEqKiXC6reGkEUUAMUEK5Ku+zbDv0BS7KMVUYQGhQ@mail.gmail.com>

Hi Geert,

Thanks for the feedback.

> Subject: Re: [PATCH v3 2/4] rtc: pcf85363: Add support for NXP pcf85263 rtc
>
> Hi Biju,
>
> On Fri, Dec 7, 2018 at 10:34 AM Biju Das <biju.das@bp.renesas.com> wrote:
> > > Subject: Re: [PATCH v3 2/4] rtc: pcf85363: Add support for NXP
> > > pcf85263 rtc
> > >
> > > On 06/12/2018 15:49:57+0000, Biju Das wrote:
>
> > > > > Subject: Re: [PATCH v3 2/4] rtc: pcf85363: Add support for NXP
> > > > > pcf85263 rtc
>
> > > > > On Thu, Dec 6, 2018 at 4:24 PM Biju Das
> > > > > <biju.das@bp.renesas.com>
> > > wrote:
> > > > > > > Subject: Re: [PATCH v3 2/4] rtc: pcf85363: Add support for
> > > > > > > NXP
> > > > > > > pcf85263 rtc CC nvmem maintainer Given bytes should be 1,
> > > > > > > val should be a pointer to a single byte...
> > > > > > > What if bytes == 0?
> > > > > >
> > > > > > I doubt we get "bytes==0" because of the checks in "
> > > > > drivers/nvmem/core.c"
> > > > > > Function " bin_attr_nvmem_read/ bin_attr_nvmem_write".
> > > > >
> > > > > Depends. There are other functions calling
> > > > > nvmem_reg_{read,write}(),
> > > e.g.
> > > > > nvmem_device_{read,write}().
> > > >
> > > > OK. In that case, I will return (-EINVAL)  for "bytes !=1"
> > >
> > > I think it is probably better to ensure the nvmem core never passes
> > > an invalid number of bytes. All the ther RTC drivers make that
> assumption.
> >
> > In that case, I will do following checks in
> > nvmem_device_{read,write}() before calling nvmem_reg_{read,write}(),
> >
> > nvmem_device_read
> >
> > /* Stop the user from reading */
> > if (offset  >= nvmem->size)
> > return 0;
> >
> > if (bytes == 0)
> > return -EINVAL;
>
> Why not 0?

Ok. Will merge with above check.

if ((offset  >= nvmem->size)  && (bytes == 0))
        return 0;

> >
> > if (offset + bytes > nvmem->size)
>
> This might overflow, please use check_add_overflow().

Will use check_add_overflow() and then the  result is compared with nvmem->size, if the check operation is successful.

> > bytes = nvmem->size - offset;
> >
> > nvmem_device_write
> >
> > /* Stop the user from writing */
> > if (offset  >= nvmem->size)
> > return -EFBIG;
>
> ENOSPC?

OK, Will change it to ENOSPC.

> + same comments as for read.
>
> Oh, and offset is unsigned int instead of loff_t.
> Nobody's envisioning nvmem devices larger than 4 GiB?

Regards,
Biju

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