netdev - Re: [PATCH v2] net: bnxt_ptp: fix compilation error

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Date:   Mon, 28 Mar 2022 15:19:01 +0900
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     Pavan Chebbi <pavan.chebbi@...adcom.com>
Cc:     Michael Chan <michael.chan@...adcom.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH v2] net: bnxt_ptp: fix compilation error

On 3/28/22 15:10, Pavan Chebbi wrote:
> On Mon, Mar 28, 2022 at 11:14 AM Damien Le Moal
> <damien.lemoal@...nsource.wdc.com> wrote:
>>
>> On 3/28/22 14:36, Michael Chan wrote:
>>> On Sun, Mar 27, 2022 at 8:35 PM Damien Le Moal
>>> <damien.lemoal@...nsource.wdc.com> wrote:
>>>>
>>>> The Broadcom bnxt_ptp driver does not compile with GCC 11.2.2 when
>>>> CONFIG_WERROR is enabled. The following error is generated:
>>>>
>>>> drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c: In function ‘bnxt_ptp_enable’:
>>>> drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c:400:43: error: array
>>>> subscript 255 is above array bounds of ‘struct pps_pin[4]’
>>>> [-Werror=array-bounds]
>>>>   400 |  ptp->pps_info.pins[pin_id].event = BNXT_PPS_EVENT_EXTERNAL;
>>>>       |  ~~~~~~~~~~~~~~~~~~^~~~~~~~
>>>> In file included from drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c:20:
>>>> drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.h:75:24: note: while
>>>> referencing ‘pins’
>>>>    75 |         struct pps_pin pins[BNXT_MAX_TSIO_PINS];
>>>>       |                        ^~~~
>>>> cc1: all warnings being treated as errors
>>>>
>>>> This is due to the function ptp_find_pin() returning a pin ID of -1 when
>>>> a valid pin is not found and this error never being checked.
>>>> Use the TSIO_PIN_VALID() macroin bnxt_ptp_enable() to check the result
>>>> of the calls to ptp_find_pin() in bnxt_ptp_enable() to fix this
>>>> compilation error.
>>>>
>>>> Fixes: 9e518f25802c ("bnxt_en: 1PPS functions to configure TSIO pins")
>>>> Cc: <stable@...r.kernel.org>
>>>> Signed-off-by: Damien Le Moal <damien.lemoal@...nsource.wdc.com>
>>>> ---
>>>> Changes from v1:
>>>> * No need to change the TSIO_PIN_VALID() macro as pin_id is an unsigned
>>>>   value.
>>>>
>>>>  drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c | 4 ++--
>>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c
>>>> index a0b321a19361..3c8fccbb9013 100644
>>>> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c
>>>> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c
>>>> @@ -390,7 +390,7 @@ static int bnxt_ptp_enable(struct ptp_clock_info *ptp_info,
>>>>                 /* Configure an External PPS IN */
>>>>                 pin_id = ptp_find_pin(ptp->ptp_clock, PTP_PF_EXTTS,
>>>>                                       rq->extts.index);
>>>> -               if (!on)
>>>> +               if (!on || !TSIO_PIN_VALID(pin_id))
>>>
>>> I think we need to return an error if !TSIO_PIN_VALID().  If we just
>>> break, we'll still use pin_id after the switch statement.
>>>
>>>>                         break;
>>>>                 rc = bnxt_ptp_cfg_pin(bp, pin_id, BNXT_PPS_PIN_PPS_IN);
>>>>                 if (rc)
>>>> @@ -403,7 +403,7 @@ static int bnxt_ptp_enable(struct ptp_clock_info *ptp_info,
>>>>                 /* Configure a Periodic PPS OUT */
>>>>                 pin_id = ptp_find_pin(ptp->ptp_clock, PTP_PF_PEROUT,
>>>>                                       rq->perout.index);
>>>> -               if (!on)
>>>> +               if (!on || !TSIO_PIN_VALID(pin_id))
>>>
>>> Same here.
>>
>> The call to bnxt_ptp_cfg_pin() after the swith will return -ENOTSUPP for
>> invalid pin IDs. So I did not feel like adding more changes was necessary.
>>
>> We can return an error if you insist, but what should it be ? -EINVAL ?
>> -ENODEV ? -ENOTSUPP ? Given that bnxt_ptp_cfg_pin() return -ENOTSUPP, we
>> could use that code.
> 
> Would it not be better if we add a check only to validate the
> ptp_find_pin is not returning -1
> explicitly? TSIO_PIN_VALID validates just the MAX side. So I think
> adding a check for -1 only
> is valid and won't duplicate the code inside the two functions.

I did that in v1, but pin_id is unsigned (u8). So changing
TSIO_PIN_VALID() to check for "pin >= 0" is a bit silly in this case.
But looking at other drivers using ptp_find_pin(), many do check the
return value first...

Sending a v3 with that check added.

> 
>>
>>>
>>>>                         break;
>>>>
>>>>                 rc = bnxt_ptp_cfg_pin(bp, pin_id, BNXT_PPS_PIN_PPS_OUT);
>>>> --
>>>> 2.35.1
>>>>
>>
>>
>> --
>> Damien Le Moal
>> Western Digital Research


-- 
Damien Le Moal
Western Digital Research