linux-kernel - Re: [PATCH] gpiolib: debugfs: display gpios requested as irq only

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Message-ID: <555A0299.3030803@linaro.org>
Date:	Mon, 18 May 2015 18:17:45 +0300
From:	"Grygorii.Strashko@...aro.org" <grygorii.strashko@...aro.org>
To:	Johan Hovold <johan@...nel.org>
CC:	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>,
	linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] gpiolib: debugfs: display gpios requested as irq only

On 05/18/2015 06:08 PM, Johan Hovold wrote:
> On Mon, May 18, 2015 at 04:06:08PM +0300, Grygorii.Strashko@...aro.org wrote:
>> On 05/18/2015 02:02 PM, Johan Hovold wrote:
>>> On Fri, May 15, 2015 at 04:25:21PM +0300, grygorii.strashko@...aro.org wrote:
>>>> From: Grygorii Strashko <grygorii.strashko@...aro.org>
>>>>
>>>> Now GPIOs, wich are requested as IRQ only, will not be displayed
>>>> through GPIO debugfs. For example:
>>>>    # cat /proc/interrupts
>>>>               CPU0       CPU1
>>>> ...
>>>> 209:          0          0  4805d000.gpio  11 Edge      0-0021
>>>>
>>>>    # cat /debug/gpio
>>>> ...
>>>> GPIOs 160-191, platform/4805d000.gpio, gpio:
>>>> <--- no info about gpio used as IRQ only here
>>>>
>>>> GPIOs 192-223, platform/48051000.gpio, gpio:
>>>>    gpio-203 (vtt_fixed           ) out hi
>>>> ...
>>>>
>>>> Hence, improve GPIO debugfs code to show such kind of gpio and print
>>>> IRQ number also. In addition, add marker "requested" for GPIOs wich
>>>> were requested by using gpioX_request().
>>>>
>>>> After this patch sys/kernel/debug/gpio will produce following output:
>>>>
>>>>    # cat /debug/gpio
>>>> ...
>>>> GPIOs 160-191, platform/4805d000.gpio, gpio:
>>>>    gpio-171 ((null)              ) in  hi IRQ209
>>>>
>>>> GPIOs 192-223, platform/48051000.gpio, gpio:
>>>>    gpio-203 (vtt_fixed           ) out hi requested
>>>
>>> This is backwards. All gpios *should* be requested. *If* we are to
>>> include not-requested gpios in the debug output, then it is those pins
>>> that need to be marked as not-requested.
>>
>> Sry, but I didn't fully understand your point here ( - Why is it
>> backward?
> 
> My main point was that you should mark the pins used for irq only
> instead of the other way round.
> 
> We should also consider making sure that pins only used for irq are also
> requested.
> 
> With the current sysfs-interface it is for example to possible to
> request the same irq, and when that pin is unexported (or only irq
> released) the pin will no longer be marked for irq (just a flag that is
> cleared) so that the direction can be changed...
> 
> gpiolib also depends on pins to be requested to prevent the
> gpio-controller driver from being unloaded while in use.
> 
> [...]
> 
>> Of course, format of the marker "requested" is discussable. Could be:
>> - "requested" --> "not-requested"
>> - "I R" or "I G" where I - IRQ, G - GPIO, R - requested
>> - etc.
> 
> How about instead of
> 
> 	GPIOs 160-191, platform/4805d000.gpio, gpio:
> 	gpio-171 ((null)              ) in  hi IRQ209
> 
> you do something like:
> 
> 	GPIOs 160-191, platform/4805d000.gpio, gpio:
> 	gpio-171 (<irq-only>          ) in  hi IRQ-209

In general agree, but i propose to do it as 
	GPIOs 160-191, platform/4805d000.gpio, gpio:
 	gpio-171 ((null)          ) in  hi IRQ-209 <irq-only>

My intention is - this interface could be considered as more or less stable, so
it is better to add additional information at the end of each line to avoid
potential breakage of User space SW (test/debug scripts).

if you agree I'll update and re-send.
 
>>> The irq-number mapping could perhaps be useful, but it should go in a
>>> separate patch. I'd suggest adding a '-' before the irq-number (e.g.
>>> "IRQ-209").
>>
>> I've thought about this, but finally decided not to split it.
>> Could be done, if you insist )
> 
> Yes, you should split self-contained, logical changes into separate
> patches (so they can be reviewed, applied or rejected separately as
> well).

np. There will be two patches
- one to display "irq-only" gpios
- second to add IRQ number

Thanks.

-- 
regards,
-grygorii
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