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

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Date:   Wed, 4 Aug 2021 06:38:05 +0800
From:   Kent Gibson <warthog618@...il.com>
To:     Dipen Patel <dipenp@...dia.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 Tue, Aug 03, 2021 at 03:41:56PM -0700, Dipen Patel wrote:
> 
> 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
> >

But I said don't bother yet.  And you need to know what errors to sanitise
before you sanitise them - unless you want to run through all the
possibilities that can be returned to userspace.

Cheers,
Kent.