linux-kernel - Re: [PATCH 09/10] PCI/VC: Use FIELD

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Date:   Wed, 11 Oct 2023 14:39:59 +0300 (EEST)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
cc:     linux-pci@...r.kernel.org,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH 09/10] PCI/VC: Use FIELD_GET()

On Tue, 10 Oct 2023, Bjorn Helgaas wrote:

> From: Bjorn Helgaas <bhelgaas@...gle.com>
> 
> Use FIELD_GET() to remove dependences on the field position, i.e., the
> shift value.  No functional change intended.
> 
> Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
> ---
>  drivers/pci/vc.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/vc.c b/drivers/pci/vc.c
> index 5fc59ac31145..a4ff7f5f66dd 100644
> --- a/drivers/pci/vc.c
> +++ b/drivers/pci/vc.c
> @@ -6,6 +6,7 @@
>   *     Author: Alex Williamson <alex.williamson@...hat.com>
>   */
>  
> +#include <linux/bitfield.h>
>  #include <linux/device.h>
>  #include <linux/kernel.h>
>  #include <linux/module.h>
> @@ -201,9 +202,9 @@ static int pci_vc_do_save_buffer(struct pci_dev *dev, int pos,
>  	/* Extended VC Count (not counting VC0) */
>  	evcc = cap1 & PCI_VC_CAP1_EVCC;
>  	/* Low Priority Extended VC Count (not counting VC0) */
> -	lpevcc = (cap1 & PCI_VC_CAP1_LPEVCC) >> 4;
> +	lpevcc = FIELD_GET(PCI_VC_CAP1_LPEVCC, cap1);
>  	/* Port Arbitration Table Entry Size (bits) */
> -	parb_size = 1 << ((cap1 & PCI_VC_CAP1_ARB_SIZE) >> 10);
> +	parb_size = 1 << FIELD_GET(PCI_VC_CAP1_ARB_SIZE, cap1);
>  
>  	/*
>  	 * Port VC Control Register contains VC Arbitration Select, which
> @@ -231,7 +232,7 @@ static int pci_vc_do_save_buffer(struct pci_dev *dev, int pos,
>  		int vcarb_offset;
>  
>  		pci_read_config_dword(dev, pos + PCI_VC_PORT_CAP2, &cap2);
> -		vcarb_offset = ((cap2 & PCI_VC_CAP2_ARB_OFF) >> 24) * 16;
> +		vcarb_offset = FIELD_GET(PCI_VC_CAP2_ARB_OFF, cap2) * 16;
>  
>  		if (vcarb_offset) {
>  			int size, vcarb_phases = 0;
> @@ -277,7 +278,7 @@ static int pci_vc_do_save_buffer(struct pci_dev *dev, int pos,
>  
>  		pci_read_config_dword(dev, pos + PCI_VC_RES_CAP +
>  				      (i * PCI_CAP_VC_PER_VC_SIZEOF), &cap);
> -		parb_offset = ((cap & PCI_VC_RES_CAP_ARB_OFF) >> 24) * 16;
> +		parb_offset = FIELD_GET(PCI_VC_RES_CAP_ARB_OFF, cap) * 16;
>  		if (parb_offset) {
>  			int size, parb_phases = 0;

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>

-- 
 i.