netdev - Re: [net-next 09/17] can: length: can_fd_len2dlc(): simplify length calculcation

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Message-ID: <a0d321d3-3e14-147d-121b-cd9074ab848e@pengutronix.de>
Date:   Thu, 14 Jan 2021 08:34:50 +0100
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Vincent MAILHOL <mailhol.vincent@...adoo.fr>
Cc:     netdev <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        linux-can <linux-can@...r.kernel.org>, kernel@...gutronix.de
Subject: Re: [net-next 09/17] can: length: can_fd_len2dlc(): simplify length
 calculcation

On 1/14/21 2:59 AM, Vincent MAILHOL wrote:
> On Tue. 14 Jan 2021 at 06:14, Marc Kleine-Budde <mkl@...gutronix.de> wrote:
>>
>> If the length paramter in len2dlc() exceeds the size of the len2dlc array, we
>> return 0xF. This is equal to the last 16 members of the array.
>>
>> This patch removes these members from the array, uses ARRAY_SIZE() for the
>> length check, and returns CANFD_MAX_DLC (which is 0xf).
>>
>> Reviewed-by: Vincent Mailhol <mailhol.vincent@...adoo.fr>
>> Link: https://lore.kernel.org/r/20210111141930.693847-9-mkl@pengutronix.de
>> Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
>> ---
>>  drivers/net/can/dev/length.c | 6 ++----
>>  1 file changed, 2 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/net/can/dev/length.c b/drivers/net/can/dev/length.c
>> index 5e7d481717ea..d695a3bee1ed 100644
>> --- a/drivers/net/can/dev/length.c
>> +++ b/drivers/net/can/dev/length.c
>> @@ -27,15 +27,13 @@ static const u8 len2dlc[] = {
>>         13, 13, 13, 13, 13, 13, 13, 13, /* 25 - 32 */
>>         14, 14, 14, 14, 14, 14, 14, 14, /* 33 - 40 */
>>         14, 14, 14, 14, 14, 14, 14, 14, /* 41 - 48 */
>> -       15, 15, 15, 15, 15, 15, 15, 15, /* 49 - 56 */
>> -       15, 15, 15, 15, 15, 15, 15, 15  /* 57 - 64 */
>>  };
>>
>>  /* map the sanitized data length to an appropriate data length code */
>>  u8 can_fd_len2dlc(u8 len)
>>  {
>> -       if (unlikely(len > 64))
>> -               return 0xF;
>> +       if (len > ARRAY_SIZE(len2dlc))
> 
> Sorry but I missed an of-by-one issue when I did my first
> review. Don't know why but it popped to my eyes this morning when
> casually reading the emails.
> 
> ARRAY_SIZE(len2dlc) is 49. If len is between 0 and 48, use the
> array, if len is greater *or equal* return CANFD_MAX_DLC.

Doh!

Looking for his brown paper bag,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
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