linux-kernel - Re: [PATCH 1/1] PCI: Use FIELD_PREP() and remove *

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Message-ID: <20231031200312.GA25127@bhelgaas>
Date:   Tue, 31 Oct 2023 15:03:12 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] PCI: Use FIELD_PREP() and remove *_SHIFT defines

On Fri, Oct 27, 2023 at 11:38:11AM +0300, Ilpo Järvinen wrote:
> Instead of open-coded masking and shifting with PCI_CONF1_* bitfields,
> use GENMASK() and FIELD_PREP(), and then remove the *_SHIFT defines
> that are no longer needed.
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> ---
> 
>  drivers/pci/pci.h | 23 ++++++++++-------------
>  1 file changed, 10 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index 39a8932dc340..31da9fde8aca 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -2,6 +2,8 @@
>  #ifndef DRIVERS_PCI_H
>  #define DRIVERS_PCI_H
>  
> +#include <linux/bitfield.h>
> +#include <linux/bits.h>
>  #include <linux/pci.h>
>  
>  /* Number of possible devfns: 0.0 to 1f.7 inclusive */
> @@ -797,19 +799,15 @@ static inline pci_power_t mid_pci_get_power_state(struct pci_dev *pdev)
>   * Section 3.2.2.3.2, Figure 3-2, p. 50.
>   */
>  
> -#define PCI_CONF1_BUS_SHIFT	16 /* Bus number */
> -#define PCI_CONF1_DEV_SHIFT	11 /* Device number */
> -#define PCI_CONF1_FUNC_SHIFT	8  /* Function number */
> -
> -#define PCI_CONF1_BUS_MASK	0xff
> -#define PCI_CONF1_DEV_MASK	0x1f
> -#define PCI_CONF1_FUNC_MASK	0x7
> +#define PCI_CONF1_BUS_MASK	GENMASK(23, 16)
> +#define PCI_CONF1_DEV_MASK	GENMASK(15, 11)
> +#define PCI_CONF1_FUNC_MASK	GENMASK(10, 8)
>  #define PCI_CONF1_REG_MASK	0xfc /* Limit aligned offset to a maximum of 256B */
>  
>  #define PCI_CONF1_ENABLE	BIT(31)
> -#define PCI_CONF1_BUS(x)	(((x) & PCI_CONF1_BUS_MASK) << PCI_CONF1_BUS_SHIFT)
> -#define PCI_CONF1_DEV(x)	(((x) & PCI_CONF1_DEV_MASK) << PCI_CONF1_DEV_SHIFT)
> -#define PCI_CONF1_FUNC(x)	(((x) & PCI_CONF1_FUNC_MASK) << PCI_CONF1_FUNC_SHIFT)
> +#define PCI_CONF1_BUS(x)	FIELD_PREP(PCI_CONF1_BUS_MASK, (x))
> +#define PCI_CONF1_DEV(x)	FIELD_PREP(PCI_CONF1_DEV_MASK, (x))
> +#define PCI_CONF1_FUNC(x)	FIELD_PREP(PCI_CONF1_FUNC_MASK, (x))
>  #define PCI_CONF1_REG(x)	((x) & PCI_CONF1_REG_MASK)

I love getting rid of the _SHIFT #defines.

I'm a dinosaur and haven't been completely converted to the wonders of
GENMASK yet.  PCI_CONF1_ADDRESS is the only user of PCI_CONF1_BUS etc,
so I think this would be simpler overall:

  #define PCI_CONF1_BUS  0x00ff0000
  #define PCI_CONF1_DEV  0x0000f800
  #define PCI_CONF1_FUNC 0x00000700
  #define PCI_CONF1_REG  0x000000ff

  #define PCI_CONF1_ADDRESS(bus, dev, func, reg) \
    (FIELD_PREP(PCI_CONF1_BUS, (bus)) | \
     FIELD_PREP(PCI_CONF1_DEV, (dev)) | \
     FIELD_PREP(PCI_CONF1_FUNC, (func)) | \
     FIELD_PREP(PCI_CONF1_REG, (reg & ~0x3)))

The v6.7 merge window just opened, and I won't start merging v6.8
material until v6.7-rc1 (probably Nov 12), so no hurry on this.

Bjorn