Re: [RFC v5 1/9] drivers/mfd: Add lookup table for Panel Control as GPIO signal

From: Thierry Reding <thierry.reding@gmail.com>
To: Shobhit Kumar <shobhit.kumar@intel.com>
Cc: Alexandre Courbot <gnurou@gmail.com>,
	Samuel Ortiz <sameo@linux.intel.com>,
	Jani Nikula <jani.nikula@intel.com>,
	intel-gfx <intel-gfx@lists.freedesktop.org>,
	Daniel Vetter <daniel.vetter@intel.com>,
	Linus Walleij <linus.walleij@linaro.org>
Subject: Re: [RFC v5 1/9] drivers/mfd: Add lookup table for Panel Control as GPIO signal
Date: Tue, 24 Mar 2015 09:51:03 +0100	[thread overview]
Message-ID: <20150324085102.GB17183@ulmo.nvidia.com> (raw)
In-Reply-To: <1426177893-17945-2-git-send-email-shobhit.kumar@intel.com>

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On Thu, Mar 12, 2015 at 10:01:25PM +0530, Shobhit Kumar wrote:
> On some Intel SoC platforms, the panel enable/disable signals are
> controlled by CRC PMIC. Add those control as a new GPIO in a lookup
> table for gpio-crystalcove chip during CRC driver load
> 
> CC: Samuel Ortiz <sameo@linux.intel.com>
> Cc: Linus Walleij <linus.walleij@linaro.org>
> Cc: Alexandre Courbot <gnurou@gmail.com>
> Cc: Thierry Reding <thierry.reding@gmail.com>
> Signed-off-by: Shobhit Kumar <shobhit.kumar@intel.com>
> ---
>  drivers/mfd/intel_soc_pmic_core.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/drivers/mfd/intel_soc_pmic_core.c b/drivers/mfd/intel_soc_pmic_core.c
> index 80cef04..365d5de 100644
> --- a/drivers/mfd/intel_soc_pmic_core.c
> +++ b/drivers/mfd/intel_soc_pmic_core.c
> @@ -24,8 +24,19 @@
>  #include <linux/acpi.h>
>  #include <linux/regmap.h>
>  #include <linux/mfd/intel_soc_pmic.h>
> +#include <linux/gpio/machine.h>
>  #include "intel_soc_pmic_core.h"
>  
> +/* Lookup table for the Panel Enable/Disable line as GPIO signals */
> +struct gpiod_lookup_table panel_gpio_table = {

Should this be static?

> +	/* Intel GFX is consumer */
> +	.dev_id = "0000:00:02.0",
> +	.table = {
> +		/* Panel EN/DISABLE */
> +		GPIO_LOOKUP("gpio_crystalcove", 94, "panel", GPIO_ACTIVE_HIGH),
> +	},
> +};
> +
>  /*
>   * On some boards the PMIC interrupt may come from a GPIO line.
>   * Try to lookup the ACPI table and see if such connection exists. If not,
> @@ -85,6 +96,9 @@ static int intel_soc_pmic_i2c_probe(struct i2c_client *i2c,
>  	if (ret)
>  		dev_warn(dev, "Can't enable IRQ as wake source: %d\n", ret);
>  
> +	/* Add lookup table binding for Panel Control to the GPIO Chip */
> +	gpiod_add_lookup_table(&panel_gpio_table);
> +

There's no corresponding gpiod_remove_lookup_table() call anywhere. That
is understandable, given that that function doesn't exist. However, this
driver can be unloaded (or at least unbound from the device), at which
point the data effectively becomes stale. This shouldn't pose much of a
problem because the driver can't be built as a module, so the data will
stick around. However, what happens if you unload and then reload the
driver? You'll be adding a second instance of the GPIO table. Given that
the data is identical maybe that isn't even a problem. Then again, it's
probably going to mess up the global list because you're adding the same
entry twice.

So I think that's something we need to fix. The same is true for the PWM
lookup table in a later patch.

Thierry

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