linux-kernel - Re: [RFC 08/11] gpiolib: cdev: Add hardware timestamp clock type

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Message-ID: <1102e1b2-9d53-fc93-b7c5-bfeb9eb2e18d@nvidia.com>
Date:   Tue, 3 Aug 2021 15:41:56 -0700
From:   Dipen Patel <dipenp@...dia.com>
To:     Kent Gibson <warthog618@...il.com>
CC:     <thierry.reding@...il.com>, <jonathanh@...dia.com>,
        <linux-kernel@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-gpio@...r.kernel.org>, <linus.walleij@...aro.org>,
        <bgolaszewski@...libre.com>, <devicetree@...r.kernel.org>,
        <linux-doc@...r.kernel.org>, <robh+dt@...nel.org>,
        <andriy.shevchenko@...ux.intel.com>
Subject: Re: [RFC 08/11] gpiolib: cdev: Add hardware timestamp clock type


On 7/30/21 11:05 PM, Kent Gibson wrote:
> On Thu, Jul 29, 2021 at 08:07:15PM -0700, Dipen Patel wrote:
>> On 7/1/21 7:24 AM, Kent Gibson wrote:
> <snip>
>>>>  			ret = gpiod_direction_output(desc, val);
>>>>  			if (ret)
>>>>  				return ret;
>>>> @@ -1152,6 +1186,13 @@ static long linereq_set_config_unlocked(struct linereq *lr,
>>>>  					polarity_change);
>>>>  			if (ret)
>>>>  				return ret;
>>>> +
>>>> +			/* Check if new config sets hardware assisted clock */
>>>> +			if (flags & GPIO_V2_LINE_FLAG_EVENT_CLOCK_HARDWARE) {
>>>> +				ret = gpiod_hw_timestamp_control(desc, true);
>>>> +				if (ret)
>>>> +					return ret;
>>>> +			}
>>>>  		}
>>>>  
>>> The error code here can come from the pinctrl timestamp_control(), so it
>>> should be sanitised before being returned to userspace.
>> I do not understand what do you mean by sanitise. I just followed what
>>
>> gpiod_direction_output did just above which also returns ret from gpio
>>
>> driver code similar to timestamp_control API.
>>
> In this context, sanitise means convert any kernel internal error codes
> to their userspace equivalent before returning them to userspace.
>
> Fair enough with the gpiod_direction_output() comparison.  I was thinking
> of a patch Andy recently submitted[1] to sanitise gpiod_request(), which
> can sometimes return EPROBE_DEFER.  But I guess we can wait until we find
> a case of a driver returning an internal error code and add a sanitiser
> then.
Make sense, I will add sanity check
>
> Cheers,
> Kent.
>
> [1] https://www.spinics.net/lists/linux-gpio/msg60998.html
>