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In-Reply-To: <20180505202450.26630-1-malat@debian.org>
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From:   Andy Shevchenko <andy.shevchenko@gmail.com>
Date:   Sun, 6 May 2018 16:58:08 +0300
Message-ID: <CAHp75VcG6qX8_BjEHpB8UGHP+bw+=E8ki8_r=-PVqv1kQUOQXQ@mail.gmail.com>
Subject: Re: [PATCH] nvmem: properly handle returned value nvmem_reg_read
To:     Mathieu Malaterre <malat@debian.org>
Cc:     Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Sat, May 5, 2018 at 11:24 PM, Mathieu Malaterre <malat@debian.org> wrote=
:
> Function nvmem_reg_read can return a non zero value indicating an error.
> This returned value must be read and error propagated to
> nvmem_cell_prepare_write_buffer.

Must is to strong word here. How come it *must*?
Did you investigate the history of the changes that brought us to current c=
ode?

How had you tested your change?
While it looks subtle it is in one of the storage class devices core,
which might be very sensible to changing workflow.

> Silence the following gcc warning (W=3D1):
>
>   drivers/nvmem/core.c:1093:9: warning: variable =E2=80=98rc=E2=80=99 set=
 but not used [-Wunused-but-set-variable]

This is least argument to accept this patch.

>
> Signed-off-by: Mathieu Malaterre <malat@debian.org>
> ---
>  drivers/nvmem/core.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
> index b05aa8e81303..f34f2363925a 100644
> --- a/drivers/nvmem/core.c
> +++ b/drivers/nvmem/core.c
> @@ -1107,6 +1107,8 @@ static void *nvmem_cell_prepare_write_buffer(struct=
 nvmem_cell *cell,
>
>                 /* setup the first byte with lsb bits from nvmem */
>                 rc =3D nvmem_reg_read(nvmem, cell->offset, &v, 1);
> +               if (rc)
> +                       goto err;
>                 *b++ |=3D GENMASK(bit_offset - 1, 0) & v;
>
>                 /* setup rest of the byte if any */
> @@ -1125,11 +1127,16 @@ static void *nvmem_cell_prepare_write_buffer(stru=
ct nvmem_cell *cell,
>                 /* setup the last byte with msb bits from nvmem */
>                 rc =3D nvmem_reg_read(nvmem,
>                                     cell->offset + cell->bytes - 1, &v, 1=
);
> +               if (rc)
> +                       goto err;
>                 *p |=3D GENMASK(7, (nbits + bit_offset) % BITS_PER_BYTE) =
& v;
>
>         }
>
>         return buf;
> +err:
> +       kfree(buf);
> +       return NULL;
>  }
>
>  /**
> --
> 2.11.0
>


--=20
With Best Regards,
Andy Shevchenko