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

[Geert Uytterhoeven <geert@linux-m68k.org>]

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?

>
> if (offset + bytes > nvmem->size)

This might overflow, please use check_add_overflow().

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

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?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds