linux-kernel - Re: [PATCH v1 1/1] mfd: intel_quark_i2c_gpio: Don't play dirty trick with const

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Message-ID: <20210326081646.GX2916463@dell>
Date:   Fri, 26 Mar 2021 08:16:46 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH v1 1/1] mfd: intel_quark_i2c_gpio: Don't play dirty trick
 with const

On Thu, 25 Mar 2021, Andy Shevchenko wrote:

> As Linus rightfully noticed, the driver plays dirty trick with const,
> i.e. it assigns a place holder data structure to the const field
> in the MFD cell and then drops the const by explicit casting. This
> is not how it should be.
> 
> Replace cell parameter by bar and assign local pointer res to the
> respective non-const place holder in the intel_quark_i2c_setup()
> and intel_quark_gpio_setup().
> 
> Reported-by: Linus Torvalds <torvalds@...ux-foundation.org>

Thanks for spotting this Linus.

> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  drivers/mfd/intel_quark_i2c_gpio.c | 26 ++++++++++++--------------
>  1 file changed, 12 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/mfd/intel_quark_i2c_gpio.c b/drivers/mfd/intel_quark_i2c_gpio.c
> index 7f90e6f022ba..f2bce2ade510 100644
> --- a/drivers/mfd/intel_quark_i2c_gpio.c
> +++ b/drivers/mfd/intel_quark_i2c_gpio.c
> @@ -157,17 +157,16 @@ static void intel_quark_unregister_i2c_clk(struct device *dev)
>  	clk_unregister(quark_mfd->i2c_clk);
>  }
>  
> -static int intel_quark_i2c_setup(struct pci_dev *pdev, struct mfd_cell *cell)
> +static int intel_quark_i2c_setup(struct pci_dev *pdev, int bar)
>  {
> +	struct mfd_cell *cell = &intel_quark_mfd_cells[bar];

What's stopping you from removing the seemingly superfluous 'bar'
parameter and simply doing:

	struct mfd_cell *cell = &intel_quark_mfd_cells[MFD_I2C_BAR];	  

> +	struct resource *res = intel_quark_i2c_res;
>  	const struct dmi_system_id *dmi_id;
>  	struct dw_i2c_platform_data *pdata;
> -	struct resource *res = (struct resource *)cell->resources;
>  	struct device *dev = &pdev->dev;
>  
> -	res[INTEL_QUARK_IORES_MEM].start =
> -		pci_resource_start(pdev, MFD_I2C_BAR);
> -	res[INTEL_QUARK_IORES_MEM].end =
> -		pci_resource_end(pdev, MFD_I2C_BAR);
> +	res[INTEL_QUARK_IORES_MEM].start = pci_resource_start(pdev, bar);
> +	res[INTEL_QUARK_IORES_MEM].end = pci_resource_end(pdev, bar);

If you do end up using 'MFD_I2C_BAR' again in here, please omit the
line wrap.  80-char lines are so 1990s!

>  	res[INTEL_QUARK_IORES_IRQ].start = pci_irq_vector(pdev, 0);
>  	res[INTEL_QUARK_IORES_IRQ].end = pci_irq_vector(pdev, 0);
> @@ -189,16 +188,15 @@ static int intel_quark_i2c_setup(struct pci_dev *pdev, struct mfd_cell *cell)
>  	return 0;
>  }

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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