linux-kernel - Re: [PATCH V2 2/3] gpio: tegra: Remove the need of keeping device handle for gpio driver

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Date:	Tue, 19 Apr 2016 10:04:20 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Laxman Dewangan <ldewangan@...dia.com>,
	Thierry Reding <thierry.reding@...il.com>
Cc:	linus.walleij@...aro.org, gnurou@...il.com,
	linux-gpio@...r.kernel.org, linux-tegra@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 2/3] gpio: tegra: Remove the need of keeping device
 handle for gpio driver

On 04/19/2016 06:43 AM, Laxman Dewangan wrote:
>
> On Tuesday 19 April 2016 06:03 PM, Thierry Reding wrote:
>> * PGP Signed by an unknown key
>>
>> On Tue, Apr 19, 2016 at 03:13:39PM +0530, Laxman Dewangan wrote:
>>> Remove the file static device handle variable for keeping device handle
>>> of driver as this is just required for error prints. The required device
>>> handle are available from gpiochip structure.
>>>
>>> Signed-off-by: Laxman Dewangan <ldewangan@...dia.com>
>>> ---
>>>   drivers/gpio/gpio-tegra.c | 8 ++++----
>>>   1 file changed, 4 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/gpio/gpio-tegra.c b/drivers/gpio/gpio-tegra.c
>>> index 1b0c497..de022a9 100644
>>> --- a/drivers/gpio/gpio-tegra.c
>>> +++ b/drivers/gpio/gpio-tegra.c
>>> @@ -80,7 +80,6 @@ struct tegra_gpio_soc_config {
>>>       u32 upper_offset;
>>>   };
>>> -static struct device *dev;
>>>   static struct irq_domain *irq_domain;
>>>   static void __iomem *regs;
>>>   static u32 tegra_gpio_bank_count;
>>> @@ -240,7 +239,8 @@ static int tegra_gpio_irq_set_type(struct
>>> irq_data *d, unsigned int type)
>>>       ret = gpiochip_lock_as_irq(&tegra_gpio_chip, gpio);
>>>       if (ret) {
>>> -        dev_err(dev, "unable to lock Tegra GPIO %d as IRQ\n", gpio);
>>> +        dev_err(tegra_gpio_chip.parent,
>>> +            "unable to lock Tegra GPIO %d as IRQ\n", gpio);
>> Can't we get rid of the tegra_gpio_chip global variable altogether? We
>> set a struct tegra_gpio_bank * as the chip data for each of the
>> interrupts, so if we added a back link to the GPIO chip to each bank
>> we could easily get at the GPIO chip (and its parent device) from the
>> IRQ chip implementation.
>>
>
> We can get rid of all the global variables and can have only one (this
> is because our REGS macros uses the stride and changing then part of
> argument is too much change for single patch) as suggested by Stephen.

The REGS macro can take a parameter that points to the struct 
tegra_gpio_chip, which in turn can point at the struct 
tegra_gpio_soc_config. That doesn't sound like too many parameters/... 
to me. There's little point getting rid of all-but-one global.