linux-kernel - Re: [PATCH 2/6] PCI: Add PCI_EXP_SLTCAP_*

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Date:   Fri, 25 Feb 2022 13:24:51 +0100
From:   Pali Rohár <pali@...nel.org>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Rob Herring <robh+dt@...nel.org>, Andrew Lunn <andrew@...n.ch>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Marek Behún <kabel@...nel.org>,
        Russell King <rmk+kernel@...linux.org.uk>,
        Gregory Clement <gregory.clement@...tlin.com>,
        linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/6] PCI: Add PCI_EXP_SLTCAP_*_SHIFT macros

On Thursday 24 February 2022 14:28:43 Bjorn Helgaas wrote:
> On Tue, Feb 22, 2022 at 05:31:54PM +0100, Pali Rohár wrote:
> > These macros allows to easily compose and extract Slot Power Limit and
> > Physical Slot Number values from Slot Capability Register.
> >
> > Signed-off-by: Pali Rohár <pali@...nel.org>
> > Signed-off-by: Marek Behún <kabel@...nel.org>
> > ---
> >  include/uapi/linux/pci_regs.h | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
> > index 108f8523fa04..3fc9a4cac630 100644
> > --- a/include/uapi/linux/pci_regs.h
> > +++ b/include/uapi/linux/pci_regs.h
> > @@ -591,10 +591,13 @@
> >  #define  PCI_EXP_SLTCAP_HPS	0x00000020 /* Hot-Plug Surprise */
> >  #define  PCI_EXP_SLTCAP_HPC	0x00000040 /* Hot-Plug Capable */
> >  #define  PCI_EXP_SLTCAP_SPLV	0x00007f80 /* Slot Power Limit Value */
> > +#define  PCI_EXP_SLTCAP_SPLV_SHIFT	7  /* Slot Power Limit Value shift */
> 
> Is there a way to use FIELD_PREP() and FIELD_GET() instead?  It seems
> like that's what the cool kids are doing now.

This is possible too.

I have proposed a patch with _SHIFT macros as this is the way how are
other macros in this file defined and used.

> At first I didn't really like them, but they do remove the need for
> adding _SHIFT macros that have to be manually related to the other.
> 
> >  #define  PCI_EXP_SLTCAP_SPLS	0x00018000 /* Slot Power Limit Scale */
> > +#define  PCI_EXP_SLTCAP_SPLS_SHIFT	15 /* Slot Power Limit Scale shift */
> >  #define  PCI_EXP_SLTCAP_EIP	0x00020000 /* Electromechanical Interlock Present */
> >  #define  PCI_EXP_SLTCAP_NCCS	0x00040000 /* No Command Completed Support */
> >  #define  PCI_EXP_SLTCAP_PSN	0xfff80000 /* Physical Slot Number */
> > +#define  PCI_EXP_SLTCAP_PSN_SHIFT	19 /* Physical Slot Number shift */
> >  #define PCI_EXP_SLTCTL		0x18	/* Slot Control */
> >  #define  PCI_EXP_SLTCTL_ABPE	0x0001	/* Attention Button Pressed Enable */
> >  #define  PCI_EXP_SLTCTL_PFDE	0x0002	/* Power Fault Detected Enable */
> > -- 
> > 2.20.1
> >