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From: Marc Zyngier <maz@kernel.org>
To: Johan Hovold <johan@kernel.org>
Cc: linux-usb@vger.kernel.org, linux-gpio@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Linus Walleij <linus.walleij@linaro.org>,
	Bartosz Golaszewski <bgolaszewski@baylibre.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	kernel-team@android.com
Subject: Re: [PATCH 1/4] gpiolib: cdev: Flag invalid GPIOs as used
Date: Mon, 07 Dec 2020 14:59:18 +0000	[thread overview]
Message-ID: <4d00047a5727a8f26d3aa4c54892cc58@kernel.org> (raw)
In-Reply-To: <X845UohmzGM7+FPu@localhost>

On 2020-12-07 14:16, Johan Hovold wrote:
> On Fri, Dec 04, 2020 at 04:47:36PM +0000, Marc Zyngier wrote:
>> When reporting the state of a GPIO to userspace, we never check
>> for the actual validity of the line, meaning we report invalid
>> lines as being usable. A subsequent request will fail though,
>> which is an inconsistent behaviour from a userspace perspective.
>> 
>> Instead, let's check for the validity of the line and report it
>> as used if it is invalid. This allows a tool such as gpioinfo
>> to report something sensible:
>> 
>> gpiochip3 - 4 lines:
>> 	line   0:      unnamed       unused   input  active-high
>> 	line   1:      unnamed       kernel   input  active-high [used]
>> 	line   2:      unnamed       kernel   input  active-high [used]
>> 	line   3:      unnamed       unused   input  active-high
>> 
>> In this example, lines 1 and 2 are invalid, and cannot be used by
>> userspace.
>> 
>> Signed-off-by: Marc Zyngier <maz@kernel.org>
>> ---
>>  drivers/gpio/gpiolib-cdev.c | 1 +
>>  1 file changed, 1 insertion(+)
>> 
>> diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
>> index e9faeaf65d14..a0fcb4ccaa02 100644
>> --- a/drivers/gpio/gpiolib-cdev.c
>> +++ b/drivers/gpio/gpiolib-cdev.c
>> @@ -1910,6 +1910,7 @@ static void gpio_desc_to_lineinfo(struct 
>> gpio_desc *desc,
>>  	    test_bit(FLAG_USED_AS_IRQ, &desc->flags) ||
>>  	    test_bit(FLAG_EXPORT, &desc->flags) ||
>>  	    test_bit(FLAG_SYSFS, &desc->flags) ||
>> +	    !gpiochip_line_is_valid(gc, info->offset) ||
>>  	    !ok_for_pinctrl)
>>  		info->flags |= GPIO_V2_LINE_FLAG_USED;
> 
> So this is somewhat separate from the rest of the series in case it
> applies also to gpio chips with reserved ranges (e.g.
> "gpio-reserved-ranges" devicetree property). Are they currently 
> reported
> as available?

I don't have any HW that uses this, but gpiolib-of.c makes use of it to
expose the valid GPIO range. I expect these systems suffer from the same
issue.

> Looks like this will work well also for USB gpio controllers with 
> static
> muxing configured in EEPROM, especially as that is how we already 
> report
> pins reported as unavailable by pinctrl (i.e. ok_for_pinctrl).

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...

  reply	other threads:[~2020-12-07 15:00 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-04 16:47 [PATCH 0/4] USB: ftdio_sio: GPIO validity fixes Marc Zyngier
2020-12-04 16:47 ` [PATCH 1/4] gpiolib: cdev: Flag invalid GPIOs as used Marc Zyngier
2020-12-07 14:16   ` Johan Hovold
2020-12-07 14:59     ` Marc Zyngier [this message]
2020-12-09  9:25   ` Linus Walleij
2020-12-04 16:47 ` [PATCH 2/4] USB: serial: ftdi_sio: Report the valid GPIO lines to gpiolib Marc Zyngier
2020-12-09  9:28   ` Linus Walleij
2020-12-04 16:47 ` [PATCH 3/4] USB: serial: ftdi_sio: Log the CBUS GPIO validity Marc Zyngier
2020-12-07 14:29   ` Johan Hovold
2020-12-07 15:00     ` Marc Zyngier
2020-12-07 15:19       ` Johan Hovold
2020-12-09  9:35         ` Linus Walleij
2020-12-09 17:05           ` Johan Hovold
2020-12-09 17:39             ` Johan Hovold
2020-12-04 16:47 ` [PATCH 4/4] USB: serial: ftdi_sio: Drop GPIO line checking dead code Marc Zyngier
2020-12-07  9:55 ` [PATCH 0/4] USB: ftdio_sio: GPIO validity fixes Andy Shevchenko
2020-12-07 14:01 ` Johan Hovold
2020-12-07 14:41   ` Marc Zyngier
2020-12-07 15:08     ` Johan Hovold
2020-12-07 15:34       ` Marc Zyngier
2020-12-07 15:49         ` Johan Hovold
2020-12-09  9:20           ` Linus Walleij
2020-12-09 15:42             ` Johan Hovold

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